Merge pull request #80 from robotpy/cpp20

Add various C++20 features

.github/workflows/dist.yml

@@ -112,6 +112,10 @@ jobs:
     - name: Install test dependencies
       run: python -m pip --disable-pip-version-check install -r tests/requirements.txt
     
+    - name: Setup MSVC compiler
+      uses: ilammy/msvc-dev-cmd@v1
+      if: matrix.os == 'windows-latest'
+
     - name: Test wheel
       shell: bash
       run: |

.readthedocs.yml

@@ -0,0 +1,15 @@
+version: 2
+
+sphinx:
+  configuration: docs/conf.py
+
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.11"
+
+python:
+  install:
+  - requirements: docs/requirements.txt
+  - method: pip
+    path: .

cxxheaderparser/lexer.py

@@ -17,7 +17,7 @@ if sys.version_info >= (3, 8):
 else:
     Protocol = object
 
-_line_re = re.compile(r'^\#[\t ]*line (\d+) "(.*)"')
+_line_re = re.compile(r'^\#[\t ]*(line)? (\d+) "(.*)"')
 _multicomment_re = re.compile("\n[\\s]+\\*")
 
 
@@ -83,6 +83,7 @@ class PlyLexer:
         "char16_t",
         "char32_t",
         "class",
+        "concept",
         "const",
         "constexpr",
         "const_cast",
@@ -121,6 +122,7 @@ class PlyLexer:
         "public",
         "register",
         "reinterpret_cast",
+        "requires",
         "return",
         "short",
         "signed",
@@ -186,6 +188,7 @@ class PlyLexer:
         "DBL_RBRACKET",
         "DBL_COLON",
         "DBL_AMP",
+        "DBL_PIPE",
         "ARROW",
         "SHIFT_LEFT",
     ] + list(keywords)
@@ -448,8 +451,8 @@ class PlyLexer:
         # handle line macros
         m = _line_re.match(t.value)
         if m:
-            self.filename = m.group(2)
-            self.line_offset = 1 + self.lex.lineno - int(m.group(1))
+            self.filename = m.group(3)
+            self.line_offset = 1 + self.lex.lineno - int(m.group(2))
             return None
         # ignore C++23 warning directive
         if t.value.startswith("#warning"):
@@ -471,6 +474,7 @@ class PlyLexer:
     t_DBL_RBRACKET = r"\]\]"
     t_DBL_COLON = r"::"
     t_DBL_AMP = r"&&"
+    t_DBL_PIPE = r"\|\|"
     t_ARROW = r"->"
     t_SHIFT_LEFT = r"<<"
     # SHIFT_RIGHT introduces ambiguity

cxxheaderparser/options.py

@@ -2,7 +2,7 @@ from dataclasses import dataclass
 from typing import Callable, Optional
 
 #: arguments are (filename, content)
-PreprocessorFunction = Callable[[str, str], str]
+PreprocessorFunction = Callable[[str, Optional[str]], str]
 
 
 @dataclass

cxxheaderparser/parser.py

@@ -22,6 +22,7 @@ from .types import (
     AutoSpecifier,
     BaseClass,
     ClassDecl,
+    Concept,
     DecltypeSpecifier,
     DecoratedType,
     EnumDecl,
@@ -74,9 +75,10 @@ class CxxParser:
     def __init__(
         self,
         filename: str,
-        content: str,
+        content: typing.Optional[str],
         visitor: CxxVisitor,
         options: typing.Optional[ParserOptions] = None,
+        encoding: typing.Optional[str] = None,
     ) -> None:
         self.visitor = visitor
         self.filename = filename
@@ -85,6 +87,13 @@ class CxxParser:
         if options and options.preprocessor is not None:
             content = options.preprocessor(filename, content)
 
+        if content is None:
+            if encoding is None:
+                encoding = "utf-8-sig"
+
+            with open(filename, "r", encoding=encoding) as fp:
+                content = fp.read()
+
         self.lex: lexer.TokenStream = lexer.LexerTokenStream(filename, content)
 
         global_ns = NamespaceDecl([], False)
@@ -529,7 +538,7 @@ class CxxParser:
             self._finish_class_decl(old_state)
 
     #
-    # Template parsing
+    # Template and concept parsing
     #
 
     def _parse_template_type_parameter(
@@ -597,9 +606,13 @@ class CxxParser:
                         lex.return_token(ptok)
                         param = self._parse_template_type_parameter(tok, None)
                     else:
-                        param = self._parse_parameter(ptok, TemplateNonTypeParam, ">")
+                        param, _ = self._parse_parameter(
+                            ptok, TemplateNonTypeParam, False, ">"
+                        )
                 else:
-                    param = self._parse_parameter(tok, TemplateNonTypeParam, ">")
+                    param, _ = self._parse_parameter(
+                        tok, TemplateNonTypeParam, concept_ok=False, end=">"
+                    )
 
                 params.append(param)
 
@@ -632,6 +645,11 @@ class CxxParser:
             self._parse_using(tok, doxygen, template)
         elif tok.type == "friend":
             self._parse_friend_decl(tok, doxygen, template)
+        elif tok.type == "concept":
+            self._parse_concept(tok, doxygen, template)
+        elif tok.type == "requires":
+            template.raw_requires_pre = self._parse_requires(tok)
+            self._parse_declarations(self.lex.token(), doxygen, template)
         else:
             self._parse_declarations(tok, doxygen, template)
 
@@ -742,6 +760,117 @@ class CxxParser:
             self.state, TemplateInst(typename, extern, doxygen)
         )
 
+    def _parse_concept(
+        self,
+        tok: LexToken,
+        doxygen: typing.Optional[str],
+        template: TemplateDecl,
+    ) -> None:
+        name = self._next_token_must_be("NAME")
+        self._next_token_must_be("=")
+
+        # not trying to understand this for now
+        raw_constraint = self._create_value(self._consume_value_until([], ",", ";"))
+
+        state = self.state
+        if isinstance(state, ClassBlockState):
+            raise CxxParseError("concept cannot be defined in a class")
+
+        self.visitor.on_concept(
+            state,
+            Concept(
+                template=template,
+                name=name.value,
+                raw_constraint=raw_constraint,
+                doxygen=doxygen,
+            ),
+        )
+
+    # fmt: off
+    _expr_operators = {
+        "<", ">", "|", "%", "^", "!", "*", "-", "+", "&", "=",
+        "&&", "||", "<<"
+    }
+    # fmt: on
+
+    def _parse_requires(
+        self,
+        tok: LexToken,
+    ) -> Value:
+        tok = self.lex.token()
+
+        rawtoks: typing.List[LexToken] = []
+
+        # The easier case -- requires requires
+        if tok.type == "requires":
+            rawtoks.append(tok)
+            for tt in ("(", "{"):
+                tok = self._next_token_must_be(tt)
+                rawtoks.extend(self._consume_balanced_tokens(tok))
+            # .. and that's it?
+
+        # this is either a parenthesized expression or a primary clause
+        elif tok.type == "(":
+            rawtoks.extend(self._consume_balanced_tokens(tok))
+        else:
+            while True:
+                if tok.type == "(":
+                    rawtoks.extend(self._consume_balanced_tokens(tok))
+                else:
+                    tok = self._parse_requires_segment(tok, rawtoks)
+
+                # If this is not an operator of some kind, we don't know how
+                # to proceed so let the next parser figure it out
+                if tok.value not in self._expr_operators:
+                    break
+
+                rawtoks.append(tok)
+
+                # check once more for compound operator?
+                tok = self.lex.token()
+                if tok.value in self._expr_operators:
+                    rawtoks.append(tok)
+                    tok = self.lex.token()
+
+            self.lex.return_token(tok)
+
+        return self._create_value(rawtoks)
+
+    def _parse_requires_segment(
+        self, tok: LexToken, rawtoks: typing.List[LexToken]
+    ) -> LexToken:
+        # first token could be a name or ::
+        if tok.type == "DBL_COLON":
+            rawtoks.append(tok)
+            tok = self.lex.token()
+
+        while True:
+            # This token has to be a name or some other valid name-like thing
+            if tok.value == "decltype":
+                rawtoks.append(tok)
+                tok = self._next_token_must_be("(")
+                rawtoks.extend(self._consume_balanced_tokens(tok))
+            elif tok.type == "NAME":
+                rawtoks.append(tok)
+            else:
+                # not sure what I expected, but I didn't find it
+                raise self._parse_error(tok)
+
+            tok = self.lex.token()
+
+            # Maybe there's a specialization
+            if tok.value == "<":
+                rawtoks.extend(self._consume_balanced_tokens(tok))
+                tok = self.lex.token()
+
+            # Maybe we keep trying to parse this name
+            if tok.type == "DBL_COLON":
+                tok = self.lex.token()
+                continue
+
+            # Let the caller decide
+            return tok
+
     #
     # Attributes
     #
@@ -1607,23 +1736,43 @@ class CxxParser:
     #
 
     def _parse_parameter(
-        self, tok: typing.Optional[LexToken], cls: typing.Type[PT], end: str = ")"
-    ) -> PT:
+        self,
+        tok: typing.Optional[LexToken],
+        cls: typing.Type[PT],
+        concept_ok: bool,
+        end: str = ")",
+    ) -> typing.Tuple[PT, typing.Optional[Type]]:
         """
         Parses a single parameter (excluding vararg parameters). Also used
         to parse template non-type parameters
+
+        Returns parameter type, abbreviated template type
         """
 
         param_name = None
         default = None
         param_pack = False
+        parsed_type: typing.Optional[Type]
+        at_type: typing.Optional[Type] = None
 
-        # required typename + decorators
-        parsed_type, mods = self._parse_type(tok)
-        if parsed_type is None:
-            raise self._parse_error(None)
+        if not tok:
+            tok = self.lex.token()
 
-        mods.validate(var_ok=False, meth_ok=False, msg="parsing parameter")
+        # placeholder type, skip typename
+        if tok.type == "auto":
+            at_type = parsed_type = Type(PQName([AutoSpecifier()]))
+        else:
+            # required typename + decorators
+            parsed_type, mods = self._parse_type(tok)
+            if parsed_type is None:
+                raise self._parse_error(None)
+
+            mods.validate(var_ok=False, meth_ok=False, msg="parsing parameter")
+
+            # Could be a concept
+            if concept_ok and self.lex.token_if("auto"):
+                at_type = Type(parsed_type.typename)
+                parsed_type.typename = PQName([AutoSpecifier()])
 
         dtype = self._parse_cv_ptr(parsed_type)
 
@@ -1651,23 +1800,32 @@ class CxxParser:
         if self.lex.token_if("="):
             default = self._create_value(self._consume_value_until([], ",", end))
 
+        # abbreviated template pack
+        if at_type and self.lex.token_if("ELLIPSIS"):
+            param_pack = True
+
         param = cls(type=dtype, name=param_name, default=default, param_pack=param_pack)
         self.debug_print("parameter: %s", param)
-        return param
+        return param, at_type
 
-    def _parse_parameters(self) -> typing.Tuple[typing.List[Parameter], bool]:
+    def _parse_parameters(
+        self, concept_ok: bool
+    ) -> typing.Tuple[typing.List[Parameter], bool, typing.List[TemplateParam]]:
         """
-        Consumes function parameters and returns them, and vararg if found
+        Consumes function parameters and returns them, and vararg if found, and
+        promotes abbreviated template parameters to actual template parameters
+        if concept_ok is True
         """
 
         # starting at a (
 
         # special case: zero parameters
         if self.lex.token_if(")"):
-            return [], False
+            return [], False, []
 
         params: typing.List[Parameter] = []
         vararg = False
+        at_params: typing.List[TemplateParam] = []
 
         while True:
             if self.lex.token_if("ELLIPSIS"):
@@ -1675,8 +1833,17 @@ class CxxParser:
                 self._next_token_must_be(")")
                 break
 
-            param = self._parse_parameter(None, Parameter)
+            param, at_type = self._parse_parameter(None, Parameter, concept_ok)
             params.append(param)
+            if at_type:
+                at_params.append(
+                    TemplateNonTypeParam(
+                        type=at_type,
+                        param_idx=len(params) - 1,
+                        param_pack=param.param_pack,
+                    )
+                )
+
             tok = self._next_token_must_be(",", ")")
             if tok.value == ")":
                 break
@@ -1691,7 +1858,7 @@ class CxxParser:
             ):
                 params = []
 
-        return params, vararg
+        return params, vararg, at_params
 
     _auto_return_typename = PQName([AutoSpecifier()])
 
@@ -1737,6 +1904,15 @@ class CxxParser:
             if otok:
                 toks = self._consume_balanced_tokens(otok)[1:-1]
             fn.noexcept = self._create_value(toks)
+        else:
+            rtok = self.lex.token_if("requires")
+            if rtok:
+                fn_template = fn.template
+                if fn_template is None:
+                    raise self._parse_error(rtok)
+                elif isinstance(fn_template, list):
+                    fn_template = fn_template[0]
+                fn_template.raw_requires_post = self._parse_requires(rtok)
 
         if self.lex.token_if("{"):
             self._discard_contents("{", "}")
@@ -1797,6 +1973,13 @@ class CxxParser:
                 if otok:
                     toks = self._consume_balanced_tokens(otok)[1:-1]
                 method.noexcept = self._create_value(toks)
+            elif tok_value == "requires":
+                method_template = method.template
+                if method_template is None:
+                    raise self._parse_error(tok)
+                elif isinstance(method_template, list):
+                    method_template = method_template[0]
+                method_template.raw_requires_post = self._parse_requires(tok)
             else:
                 self.lex.return_token(tok)
                 break
@@ -1838,7 +2021,16 @@ class CxxParser:
         state.location = location
         is_class_block = isinstance(state, ClassBlockState)
 
-        params, vararg = self._parse_parameters()
+        params, vararg, at_params = self._parse_parameters(True)
+
+        # Promote abbreviated template parameters
+        if at_params:
+            if template is None:
+                template = TemplateDecl(at_params)
+            elif isinstance(template, TemplateDecl):
+                template.params.extend(at_params)
+            else:
+                template[-1].params.extend(at_params)
 
         # A method outside of a class has multiple name segments
         multiple_name_segments = len(pqname.segments) > 1
@@ -2011,7 +2203,7 @@ class CxxParser:
                     toks = self._consume_balanced_tokens(gtok)
                     self.lex.return_tokens(toks[1:-1])
 
-                fn_params, vararg = self._parse_parameters()
+                fn_params, vararg, _ = self._parse_parameters(False)
 
                 assert not isinstance(dtype, FunctionType)
                 dtype = dtype_fn = FunctionType(dtype, fn_params, vararg)
@@ -2039,7 +2231,7 @@ class CxxParser:
                         assert not isinstance(dtype, FunctionType)
                         dtype = self._parse_array_type(aptok, dtype)
                     elif aptok.type == "(":
-                        fn_params, vararg = self._parse_parameters()
+                        fn_params, vararg, _ = self._parse_parameters(False)
                         # the type we already have is the return type of the function pointer
 
                         assert not isinstance(dtype, FunctionType)

cxxheaderparser/preprocessor.py

@@ -1,37 +1,248 @@
 """
-Contains optional preprocessor support via pcpp
+Contains optional preprocessor support functions
 """
 
 import io
 import re
 import os
+import subprocess
+import sys
+import tempfile
 import typing
-from .options import PreprocessorFunction
 
-from pcpp import Preprocessor, OutputDirective, Action
+from .options import PreprocessorFunction
 
 
 class PreprocessorError(Exception):
     pass
 
 
-class _CustomPreprocessor(Preprocessor):
-    def __init__(self, encoding: typing.Optional[str]):
-        Preprocessor.__init__(self)
-        self.errors: typing.List[str] = []
-        self.assume_encoding = encoding
-
-    def on_error(self, file, line, msg):
-        self.errors.append(f"{file}:{line} error: {msg}")
-
-    def on_include_not_found(self, *ignored):
-        raise OutputDirective(Action.IgnoreAndPassThrough)
-
-    def on_comment(self, *ignored):
-        return True
+#
+# GCC preprocessor support
+#
 
 
-def _filter_self(fname: str, fp: typing.TextIO) -> str:
+def _gcc_filter(fname: str, fp: typing.TextIO) -> str:
+    new_output = io.StringIO()
+    keep = True
+    fname = fname.replace("\\", "\\\\")
+
+    for line in fp:
+        if line.startswith("# "):
+            last_quote = line.rfind('"')
+            if last_quote != -1:
+                keep = line[:last_quote].endswith(fname)
+
+        if keep:
+            new_output.write(line)
+
+    new_output.seek(0)
+    return new_output.read()
+
+
+def make_gcc_preprocessor(
+    *,
+    defines: typing.List[str] = [],
+    include_paths: typing.List[str] = [],
+    retain_all_content: bool = False,
+    encoding: typing.Optional[str] = None,
+    gcc_args: typing.List[str] = ["g++"],
+    print_cmd: bool = True,
+) -> PreprocessorFunction:
+    """
+    Creates a preprocessor function that uses g++ to preprocess the input text.
+
+    gcc is a high performance and accurate precompiler, but if an #include
+    directive can't be resolved or other oddity exists in your input it will
+    throw an error.
+
+    :param defines: list of #define macros specified as "key value"
+    :param include_paths: list of directories to search for included files
+    :param retain_all_content: If False, only the parsed file content will be retained
+    :param encoding: If specified any include files are opened with this encoding
+    :param gcc_args: This is the path to G++ and any extra args you might want
+    :param print_cmd: Prints the gcc command as its executed
+
+    .. code-block:: python
+
+        pp = make_gcc_preprocessor()
+        options = ParserOptions(preprocessor=pp)
+
+        parse_file(content, options=options)
+
+    """
+
+    if not encoding:
+        encoding = "utf-8"
+
+    def _preprocess_file(filename: str, content: typing.Optional[str]) -> str:
+        cmd = gcc_args + ["-w", "-E", "-C"]
+
+        for p in include_paths:
+            cmd.append(f"-I{p}")
+        for d in defines:
+            cmd.append(f"-D{d.replace(' ', '=')}")
+
+        kwargs = {"encoding": encoding}
+        if filename == "<str>":
+            cmd.append("-")
+            filename = "<stdin>"
+            if content is None:
+                raise PreprocessorError("no content specified for stdin")
+            kwargs["input"] = content
+        else:
+            cmd.append(filename)
+
+        if print_cmd:
+            print("+", " ".join(cmd), file=sys.stderr)
+
+        result: str = subprocess.check_output(cmd, **kwargs)  # type: ignore
+        if not retain_all_content:
+            result = _gcc_filter(filename, io.StringIO(result))
+
+        return result
+
+    return _preprocess_file
+
+
+#
+# Microsoft Visual Studio preprocessor support
+#
+
+
+def _msvc_filter(fp: typing.TextIO) -> str:
+    # MSVC outputs the original file as the very first #line directive
+    # so we just use that
+    new_output = io.StringIO()
+    keep = True
+
+    first = fp.readline()
+    assert first.startswith("#line")
+    fname = first[first.find('"') :]
+
+    for line in fp:
+        if line.startswith("#line"):
+            keep = line.endswith(fname)
+
+        if keep:
+            new_output.write(line)
+
+    new_output.seek(0)
+    return new_output.read()
+
+
+def make_msvc_preprocessor(
+    *,
+    defines: typing.List[str] = [],
+    include_paths: typing.List[str] = [],
+    retain_all_content: bool = False,
+    encoding: typing.Optional[str] = None,
+    msvc_args: typing.List[str] = ["cl.exe"],
+    print_cmd: bool = True,
+) -> PreprocessorFunction:
+    """
+    Creates a preprocessor function that uses cl.exe from Microsoft Visual Studio
+    to preprocess the input text. cl.exe is not typically on the path, so you
+    may need to open the correct developer tools shell or pass in the correct path
+    to cl.exe in the `msvc_args` parameter.
+
+    cl.exe will throw an error if a file referenced by an #include directive is not found.
+
+    :param defines: list of #define macros specified as "key value"
+    :param include_paths: list of directories to search for included files
+    :param retain_all_content: If False, only the parsed file content will be retained
+    :param encoding: If specified any include files are opened with this encoding
+    :param msvc_args: This is the path to cl.exe and any extra args you might want
+    :param print_cmd: Prints the command as its executed
+
+    .. code-block:: python
+
+        pp = make_msvc_preprocessor()
+        options = ParserOptions(preprocessor=pp)
+
+        parse_file(content, options=options)
+
+    """
+
+    if not encoding:
+        encoding = "utf-8"
+
+    def _preprocess_file(filename: str, content: typing.Optional[str]) -> str:
+        cmd = msvc_args + ["/nologo", "/E", "/C"]
+
+        for p in include_paths:
+            cmd.append(f"/I{p}")
+        for d in defines:
+            cmd.append(f"/D{d.replace(' ', '=')}")
+
+        tfpname = None
+
+        try:
+            kwargs = {"encoding": encoding}
+            if filename == "<str>":
+                if content is None:
+                    raise PreprocessorError("no content specified for stdin")
+
+                tfp = tempfile.NamedTemporaryFile(
+                    mode="w", encoding=encoding, suffix=".h", delete=False
+                )
+                tfpname = tfp.name
+                tfp.write(content)
+                tfp.close()
+
+                cmd.append(tfpname)
+            else:
+                cmd.append(filename)
+
+            if print_cmd:
+                print("+", " ".join(cmd), file=sys.stderr)
+
+            result: str = subprocess.check_output(cmd, **kwargs)  # type: ignore
+            if not retain_all_content:
+                result = _msvc_filter(io.StringIO(result))
+        finally:
+            if tfpname:
+                os.unlink(tfpname)
+
+        return result
+
+    return _preprocess_file
+
+
+#
+# PCPP preprocessor support (not installed by default)
+#
+
+
+try:
+    import pcpp
+    from pcpp import Preprocessor, OutputDirective, Action
+
+    class _CustomPreprocessor(Preprocessor):
+        def __init__(
+            self,
+            encoding: typing.Optional[str],
+            passthru_includes: typing.Optional["re.Pattern"],
+        ):
+            Preprocessor.__init__(self)
+            self.errors: typing.List[str] = []
+            self.assume_encoding = encoding
+            self.passthru_includes = passthru_includes
+
+        def on_error(self, file, line, msg):
+            self.errors.append(f"{file}:{line} error: {msg}")
+
+        def on_include_not_found(self, *ignored):
+            raise OutputDirective(Action.IgnoreAndPassThrough)
+
+        def on_comment(self, *ignored):
+            return True
+
+except ImportError:
+    pcpp = None
+
+
+def _pcpp_filter(fname: str, fp: typing.TextIO) -> str:
     # the output of pcpp includes the contents of all the included files, which
     # isn't what a typical user of cxxheaderparser would want, so we strip out
     # the line directives and any content that isn't in our original file
@@ -58,12 +269,22 @@ def make_pcpp_preprocessor(
     include_paths: typing.List[str] = [],
     retain_all_content: bool = False,
     encoding: typing.Optional[str] = None,
+    passthru_includes: typing.Optional["re.Pattern"] = None,
 ) -> PreprocessorFunction:
     """
     Creates a preprocessor function that uses pcpp (which must be installed
     separately) to preprocess the input text.
 
+    If missing #include files are encountered, this preprocessor will ignore the
+    error. This preprocessor is pure python so it's very portable, and is a good
+    choice if performance isn't critical.
+
+    :param defines: list of #define macros specified as "key value"
+    :param include_paths: list of directories to search for included files
+    :param retain_all_content: If False, only the parsed file content will be retained
     :param encoding: If specified any include files are opened with this encoding
+    :param passthru_includes: If specified any #include directives that match the
+                              compiled regex pattern will be part of the output.
 
     .. code-block:: python
 
@@ -74,8 +295,11 @@ def make_pcpp_preprocessor(
 
     """
 
-    def _preprocess_file(filename: str, content: str) -> str:
-        pp = _CustomPreprocessor(encoding)
+    if pcpp is None:
+        raise PreprocessorError("pcpp is not installed")
+
+    def _preprocess_file(filename: str, content: typing.Optional[str]) -> str:
+        pp = _CustomPreprocessor(encoding, passthru_includes)
         if include_paths:
             for p in include_paths:
                 pp.add_path(p)
@@ -86,6 +310,10 @@ def make_pcpp_preprocessor(
         if not retain_all_content:
             pp.line_directive = "#line"
 
+        if content is None:
+            with open(filename, "r", encoding=encoding) as fp:
+                content = fp.read()
+
         pp.parse(content, filename)
 
         if pp.errors:
@@ -111,6 +339,6 @@ def make_pcpp_preprocessor(
                         filename = filename.replace(os.sep, "/")
                     break
 
-            return _filter_self(filename, fp)
+            return _pcpp_filter(filename, fp)
 
     return _preprocess_file

cxxheaderparser/simple.py

@@ -34,6 +34,7 @@ from dataclasses import dataclass, field
 
 from .types import (
     ClassDecl,
+    Concept,
     EnumDecl,
     Field,
     ForwardDecl,
@@ -113,6 +114,9 @@ class NamespaceScope:
     using_alias: typing.List[UsingAlias] = field(default_factory=list)
     ns_alias: typing.List[NamespaceAlias] = field(default_factory=list)
 
+    #: Concepts
+    concepts: typing.List[Concept] = field(default_factory=list)
+
     #: Explicit template instantiations
     template_insts: typing.List[TemplateInst] = field(default_factory=list)
 
@@ -243,6 +247,9 @@ class SimpleCxxVisitor:
     def on_namespace_end(self, state: SNamespaceBlockState) -> None:
         pass
 
+    def on_concept(self, state: SNonClassBlockState, concept: Concept) -> None:
+        state.user_data.concepts.append(concept)
+
     def on_namespace_alias(
         self, state: SNonClassBlockState, alias: NamespaceAlias
     ) -> None:
@@ -348,7 +355,10 @@ def parse_file(
     if filename == "-":
         content = sys.stdin.read()
     else:
-        with open(filename, encoding=encoding) as fp:
-            content = fp.read()
+        content = None
 
-    return parse_string(content, filename=filename, options=options)
+    visitor = SimpleCxxVisitor()
+    parser = CxxParser(filename, content, visitor, options)
+    parser.parse()
+
+    return visitor.data

cxxheaderparser/types.py

@@ -454,12 +454,19 @@ class TemplateNonTypeParam:
 
        template <auto T>
                  ~~~~~~
+
+       // abbreviated template parameters are converted to this and param_idx is set
+       void fn(C auto p)
+               ~~~~~~
     """
 
     type: DecoratedType
     name: typing.Optional[str] = None
     default: typing.Optional[Value] = None
 
+    #: If this was promoted, the parameter index that this corresponds with
+    param_idx: typing.Optional[int] = None
+
     #: Contains a ``...``
     param_pack: bool = False
 
@@ -513,6 +520,15 @@ class TemplateDecl:
 
     params: typing.List[TemplateParam] = field(default_factory=list)
 
+    # Currently don't interpret requires, if that changes in the future
+    # then this API will change.
+
+    #: template <typename T> requires ...
+    raw_requires_pre: typing.Optional[Value] = None
+
+    #: template <typename T> int main() requires ...
+    raw_requires_post: typing.Optional[Value] = None
+
 
 #: If no template, this is None. This is a TemplateDecl if this there is a single
 #: declaration:
@@ -551,6 +567,31 @@ class TemplateInst:
     doxygen: typing.Optional[str] = None
 
 
+@dataclass
+class Concept:
+    """
+    Preliminary support for consuming headers that contain concepts, but
+    not trying to actually make sense of them at this time. If this is
+    something you care about, pull requests are welcomed!
+
+    .. code-block:: c++
+
+        template <class T>
+        concept Meowable = is_meowable<T>;
+
+        template<typename T>
+        concept Addable = requires (T x) { x + x; };
+    """
+
+    template: TemplateDecl
+    name: str
+
+    #: In the future this will be removed if we fully parse the expression
+    raw_constraint: Value
+
+    doxygen: typing.Optional[str] = None
+
+
 @dataclass
 class ForwardDecl:
     """

cxxheaderparser/visitor.py

@@ -8,6 +8,7 @@ else:
 
 
 from .types import (
+    Concept,
     EnumDecl,
     Field,
     ForwardDecl,
@@ -89,6 +90,14 @@ class CxxVisitor(Protocol):
         Called when a ``namespace`` alias is encountered
         """
 
+    def on_concept(self, state: NonClassBlockState, concept: Concept) -> None:
+        """
+        .. code-block:: c++
+
+            template <class T>
+            concept Meowable = is_meowable<T>;
+        """
+
     def on_forward_decl(self, state: State, fdecl: ForwardDecl) -> None:
         """
         Called when a forward declaration is encountered
@@ -254,6 +263,9 @@ class NullVisitor:
     def on_namespace_end(self, state: NamespaceBlockState) -> None:
         return None
 
+    def on_concept(self, state: NonClassBlockState, concept: Concept) -> None:
+        return None
+
     def on_namespace_alias(
         self, state: NonClassBlockState, alias: NamespaceAlias
     ) -> None:

docs/conf.py

@@ -12,27 +12,19 @@ import pkg_resources
 # -- Project information -----------------------------------------------------
 
 project = "cxxheaderparser"
-copyright = "2020-2021, Dustin Spicuzza"
+copyright = "2020-2023, Dustin Spicuzza"
 author = "Dustin Spicuzza"
 
 # The full version, including alpha/beta/rc tags
 release = pkg_resources.get_distribution("cxxheaderparser").version
 
-# -- RTD configuration ------------------------------------------------
-
-# on_rtd is whether we are on readthedocs.org, this line of code grabbed from docs.readthedocs.org
-on_rtd = os.environ.get("READTHEDOCS", None) == "True"
-
 
 # -- General configuration ---------------------------------------------------
 
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = [
-    "sphinx.ext.autodoc",
-    "sphinx_autodoc_typehints",
-]
+extensions = ["sphinx.ext.autodoc", "sphinx_autodoc_typehints", "sphinx_rtd_theme"]
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ["_templates"]
@@ -47,13 +39,7 @@ exclude_patterns = ["_build", "Thumbs.db", ".DS_Store"]
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-#
-if not on_rtd:  # only import and set the theme if we're building docs locally
-    import sphinx_rtd_theme
 
-    html_theme = "sphinx_rtd_theme"
-    html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
-else:
-    html_theme = "default"
+html_theme = "sphinx_rtd_theme"
 
 always_document_param_types = True

tests/test_abv_template.py

@@ -0,0 +1,353 @@
+# Note: testcases generated via `python -m cxxheaderparser.gentest`
+#
+# Tests various aspects of abbreviated function templates
+#
+
+from cxxheaderparser.simple import NamespaceScope, ParsedData, parse_string
+from cxxheaderparser.types import (
+    AutoSpecifier,
+    Function,
+    FundamentalSpecifier,
+    NameSpecifier,
+    PQName,
+    Parameter,
+    Pointer,
+    Reference,
+    TemplateDecl,
+    TemplateNonTypeParam,
+    Type,
+)
+
+
+def test_abv_template_f1() -> None:
+    content = """
+      void f1(auto);       // same as template<class T> void f1(T)
+      void f1p(auto p);
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f1")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(typename=PQName(segments=[AutoSpecifier()]))
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(typename=PQName(segments=[AutoSpecifier()])),
+                                param_idx=0,
+                            )
+                        ]
+                    ),
+                ),
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f1p")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(typename=PQName(segments=[AutoSpecifier()])),
+                            name="p",
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(typename=PQName(segments=[AutoSpecifier()])),
+                                param_idx=0,
+                            )
+                        ]
+                    ),
+                ),
+            ]
+        )
+    )
+
+
+def test_abv_template_f2() -> None:
+    content = """
+      void f2(C1 auto);    // same as template<C1 T> void f2(T), if C1 is a concept
+      void f2p(C1 auto p);
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f2")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(typename=PQName(segments=[AutoSpecifier()]))
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="C1")])
+                                ),
+                                param_idx=0,
+                            )
+                        ]
+                    ),
+                ),
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f2p")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(typename=PQName(segments=[AutoSpecifier()])),
+                            name="p",
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="C1")])
+                                ),
+                                param_idx=0,
+                            )
+                        ]
+                    ),
+                ),
+            ]
+        )
+    )
+
+
+def test_abv_template_f3() -> None:
+    content = """
+      void f3(C2 auto...);     // same as template<C2... Ts> void f3(Ts...), if C2 is a
+                               // concept
+      void f3p(C2 auto p...);
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f3")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(typename=PQName(segments=[AutoSpecifier()])),
+                            param_pack=True,
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="C2")])
+                                ),
+                                param_idx=0,
+                                param_pack=True,
+                            )
+                        ]
+                    ),
+                ),
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f3p")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(typename=PQName(segments=[AutoSpecifier()])),
+                            name="p",
+                            param_pack=True,
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="C2")])
+                                ),
+                                param_idx=0,
+                                param_pack=True,
+                            )
+                        ]
+                    ),
+                ),
+            ]
+        )
+    )
+
+
+def test_abv_template_f4() -> None:
+    content = """
+      void f4(C2 auto, ...);   // same as template<C2 T> void f4(T...), if C2 is a concept
+      void f4p(C2 auto p,...);
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f4")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(typename=PQName(segments=[AutoSpecifier()]))
+                        )
+                    ],
+                    vararg=True,
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="C2")])
+                                ),
+                                param_idx=0,
+                            )
+                        ]
+                    ),
+                ),
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f4p")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(typename=PQName(segments=[AutoSpecifier()])),
+                            name="p",
+                        )
+                    ],
+                    vararg=True,
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="C2")])
+                                ),
+                                param_idx=0,
+                            )
+                        ]
+                    ),
+                ),
+            ]
+        )
+    )
+
+
+def test_abv_template_f5() -> None:
+    content = """
+      void f5(const C3 auto *, C4 auto &);       // same as template<C3 T, C4 U> void f5(const T*, U&);
+      void f5p(const C3 auto * p1, C4 auto &p2);
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f5")]),
+                    parameters=[
+                        Parameter(
+                            type=Pointer(
+                                ptr_to=Type(
+                                    typename=PQName(
+                                        segments=[AutoSpecifier()],
+                                    ),
+                                    const=True,
+                                )
+                            )
+                        ),
+                        Parameter(
+                            type=Reference(
+                                ref_to=Type(typename=PQName(segments=[AutoSpecifier()]))
+                            )
+                        ),
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(
+                                        segments=[NameSpecifier(name="C3")]
+                                    ),
+                                ),
+                                param_idx=0,
+                            ),
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="C4")])
+                                ),
+                                param_idx=1,
+                            ),
+                        ]
+                    ),
+                ),
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f5p")]),
+                    parameters=[
+                        Parameter(
+                            type=Pointer(
+                                ptr_to=Type(
+                                    typename=PQName(
+                                        segments=[AutoSpecifier()],
+                                    ),
+                                    const=True,
+                                )
+                            ),
+                            name="p1",
+                        ),
+                        Parameter(
+                            type=Reference(
+                                ref_to=Type(typename=PQName(segments=[AutoSpecifier()]))
+                            ),
+                            name="p2",
+                        ),
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(
+                                        segments=[NameSpecifier(name="C3")]
+                                    ),
+                                ),
+                                param_idx=0,
+                            ),
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="C4")])
+                                ),
+                                param_idx=1,
+                            ),
+                        ]
+                    ),
+                ),
+            ]
+        )
+    )

tests/test_concepts.py

@@ -0,0 +1,811 @@
+from cxxheaderparser.simple import ClassScope, NamespaceScope, ParsedData, parse_string
+from cxxheaderparser.tokfmt import Token
+from cxxheaderparser.types import (
+    AutoSpecifier,
+    ClassDecl,
+    Concept,
+    Function,
+    FundamentalSpecifier,
+    MoveReference,
+    NameSpecifier,
+    PQName,
+    Parameter,
+    TemplateArgument,
+    TemplateDecl,
+    TemplateNonTypeParam,
+    TemplateSpecialization,
+    TemplateTypeParam,
+    Type,
+    Value,
+    Variable,
+)
+
+
+def test_concept_basic_constraint() -> None:
+    content = """
+      template <class T, class U>
+      concept Derived = std::is_base_of<U, T>::value;
+
+      template <Derived<Base> T> void f(T); // T is constrained by Derived<T, Base>
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            )
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(
+                                        segments=[
+                                            NameSpecifier(
+                                                name="Derived",
+                                                specialization=TemplateSpecialization(
+                                                    args=[
+                                                        TemplateArgument(
+                                                            arg=Type(
+                                                                typename=PQName(
+                                                                    segments=[
+                                                                        NameSpecifier(
+                                                                            name="Base"
+                                                                        )
+                                                                    ]
+                                                                )
+                                                            )
+                                                        )
+                                                    ]
+                                                ),
+                                            )
+                                        ]
+                                    )
+                                ),
+                                name="T",
+                            )
+                        ]
+                    ),
+                )
+            ],
+            concepts=[
+                Concept(
+                    template=TemplateDecl(
+                        params=[
+                            TemplateTypeParam(typekey="class", name="T"),
+                            TemplateTypeParam(typekey="class", name="U"),
+                        ]
+                    ),
+                    name="Derived",
+                    raw_constraint=Value(
+                        tokens=[
+                            Token(value="std"),
+                            Token(value="::"),
+                            Token(value="is_base_of"),
+                            Token(value="<"),
+                            Token(value="U"),
+                            Token(value=","),
+                            Token(value="T"),
+                            Token(value=">"),
+                            Token(value="::"),
+                            Token(value="value"),
+                        ]
+                    ),
+                )
+            ],
+        )
+    )
+
+
+def test_concept_basic_constraint2() -> None:
+    content = """
+      template <class T> constexpr bool is_meowable = true;
+
+      template <class T> constexpr bool is_cat = true;
+
+      template <class T>
+      concept Meowable = is_meowable<T>;
+
+      template <class T>
+      concept BadMeowableCat = is_meowable<T> && is_cat<T>;
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            variables=[
+                Variable(
+                    name=PQName(segments=[NameSpecifier(name="is_meowable")]),
+                    type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="bool")])
+                    ),
+                    value=Value(tokens=[Token(value="true")]),
+                    constexpr=True,
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="class", name="T")]
+                    ),
+                ),
+                Variable(
+                    name=PQName(segments=[NameSpecifier(name="is_cat")]),
+                    type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="bool")])
+                    ),
+                    value=Value(tokens=[Token(value="true")]),
+                    constexpr=True,
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="class", name="T")]
+                    ),
+                ),
+            ],
+            concepts=[
+                Concept(
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="class", name="T")]
+                    ),
+                    name="Meowable",
+                    raw_constraint=Value(
+                        tokens=[
+                            Token(value="is_meowable"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                        ]
+                    ),
+                ),
+                Concept(
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="class", name="T")]
+                    ),
+                    name="BadMeowableCat",
+                    raw_constraint=Value(
+                        tokens=[
+                            Token(value="is_meowable"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                            Token(value="&&"),
+                            Token(value="is_cat"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                        ]
+                    ),
+                ),
+            ],
+        )
+    )
+
+
+def test_concept_basic_requires() -> None:
+    content = """
+      template <typename T>
+      concept Hashable = requires(T a) {
+        { std::hash<T>{}(a) } -> std::convertible_to<std::size_t>;
+      };
+
+      template <Hashable T> void f(T) {}
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            )
+                        )
+                    ],
+                    has_body=True,
+                    template=TemplateDecl(
+                        params=[
+                            TemplateNonTypeParam(
+                                type=Type(
+                                    typename=PQName(
+                                        segments=[NameSpecifier(name="Hashable")]
+                                    )
+                                ),
+                                name="T",
+                            )
+                        ]
+                    ),
+                )
+            ],
+            concepts=[
+                Concept(
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="typename", name="T")]
+                    ),
+                    name="Hashable",
+                    raw_constraint=Value(
+                        tokens=[
+                            Token(value="requires"),
+                            Token(value="("),
+                            Token(value="T"),
+                            Token(value="a"),
+                            Token(value=")"),
+                            Token(value="{"),
+                            Token(value="{"),
+                            Token(value="std"),
+                            Token(value="::"),
+                            Token(value="hash"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                            Token(value="{"),
+                            Token(value="}"),
+                            Token(value="("),
+                            Token(value="a"),
+                            Token(value=")"),
+                            Token(value="}"),
+                            Token(value="->"),
+                            Token(value="std"),
+                            Token(value="::"),
+                            Token(value="convertible_to"),
+                            Token(value="<"),
+                            Token(value="std"),
+                            Token(value="::"),
+                            Token(value="size_t"),
+                            Token(value=">"),
+                            Token(value=";"),
+                            Token(value="}"),
+                        ]
+                    ),
+                )
+            ],
+        )
+    )
+
+
+def test_concept_nested_requirements() -> None:
+    content = """
+      template<class T>
+      concept Semiregular = DefaultConstructible<T> &&
+          CopyConstructible<T> && CopyAssignable<T> && Destructible<T> &&
+      requires(T a, std::size_t n)
+      {
+          requires Same<T*, decltype(&a)>; // nested: "Same<...> evaluates to true"
+          { a.~T() } noexcept; // compound: "a.~T()" is a valid expression that doesn't throw
+          requires Same<T*, decltype(new T)>; // nested: "Same<...> evaluates to true"
+          requires Same<T*, decltype(new T[n])>; // nested
+          { delete new T }; // compound
+          { delete new T[n] }; // compound
+      };
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            concepts=[
+                Concept(
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="class", name="T")]
+                    ),
+                    name="Semiregular",
+                    raw_constraint=Value(
+                        tokens=[
+                            Token(value="DefaultConstructible"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                            Token(value="&&"),
+                            Token(value="CopyConstructible"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                            Token(value="&&"),
+                            Token(value="CopyAssignable"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                            Token(value="&&"),
+                            Token(value="Destructible"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                            Token(value="&&"),
+                            Token(value="requires"),
+                            Token(value="("),
+                            Token(value="T"),
+                            Token(value="a"),
+                            Token(value=","),
+                            Token(value="std"),
+                            Token(value="::"),
+                            Token(value="size_t"),
+                            Token(value="n"),
+                            Token(value=")"),
+                            Token(value="{"),
+                            Token(value="requires"),
+                            Token(value="Same"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value="*"),
+                            Token(value=","),
+                            Token(value="decltype"),
+                            Token(value="("),
+                            Token(value="&"),
+                            Token(value="a"),
+                            Token(value=")"),
+                            Token(value=">"),
+                            Token(value=";"),
+                            Token(value="{"),
+                            Token(value="a"),
+                            Token(value="."),
+                            Token(value="~T"),
+                            Token(value="("),
+                            Token(value=")"),
+                            Token(value="}"),
+                            Token(value="noexcept"),
+                            Token(value=";"),
+                            Token(value="requires"),
+                            Token(value="Same"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value="*"),
+                            Token(value=","),
+                            Token(value="decltype"),
+                            Token(value="("),
+                            Token(value="new"),
+                            Token(value="T"),
+                            Token(value=")"),
+                            Token(value=">"),
+                            Token(value=";"),
+                            Token(value="requires"),
+                            Token(value="Same"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value="*"),
+                            Token(value=","),
+                            Token(value="decltype"),
+                            Token(value="("),
+                            Token(value="new"),
+                            Token(value="T"),
+                            Token(value="["),
+                            Token(value="n"),
+                            Token(value="]"),
+                            Token(value=")"),
+                            Token(value=">"),
+                            Token(value=";"),
+                            Token(value="{"),
+                            Token(value="delete"),
+                            Token(value="new"),
+                            Token(value="T"),
+                            Token(value="}"),
+                            Token(value=";"),
+                            Token(value="{"),
+                            Token(value="delete"),
+                            Token(value="new"),
+                            Token(value="T"),
+                            Token(value="["),
+                            Token(value="n"),
+                            Token(value="]"),
+                            Token(value="}"),
+                            Token(value=";"),
+                            Token(value="}"),
+                        ]
+                    ),
+                )
+            ]
+        )
+    )
+
+
+def test_concept_requires_class() -> None:
+    content = """
+      // clang-format off
+      template <typename T>
+      concept Number = std::integral<T> || std::floating_point<T>;
+
+      template <typename T>
+      requires Number<T>
+      struct WrappedNumber {};
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            classes=[
+                ClassScope(
+                    class_decl=ClassDecl(
+                        typename=PQName(
+                            segments=[NameSpecifier(name="WrappedNumber")],
+                            classkey="struct",
+                        ),
+                        template=TemplateDecl(
+                            params=[TemplateTypeParam(typekey="typename", name="T")],
+                            raw_requires_pre=Value(
+                                tokens=[
+                                    Token(value="Number"),
+                                    Token(value="<"),
+                                    Token(value="T"),
+                                    Token(value=">"),
+                                ]
+                            ),
+                        ),
+                    )
+                )
+            ],
+            concepts=[
+                Concept(
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="typename", name="T")]
+                    ),
+                    name="Number",
+                    raw_constraint=Value(
+                        tokens=[
+                            Token(value="std"),
+                            Token(value="::"),
+                            Token(value="integral"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                            Token(value="||"),
+                            Token(value="std"),
+                            Token(value="::"),
+                            Token(value="floating_point"),
+                            Token(value="<"),
+                            Token(value="T"),
+                            Token(value=">"),
+                        ]
+                    ),
+                )
+            ],
+        )
+    )
+
+
+def test_requires_last_elem() -> None:
+    content = """
+      template<typename T>
+      void f(T&&) requires Eq<T>;  // can appear as the last element of a function declarator
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="f")]),
+                    parameters=[
+                        Parameter(
+                            type=MoveReference(
+                                moveref_to=Type(
+                                    typename=PQName(segments=[NameSpecifier(name="T")])
+                                )
+                            )
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="typename", name="T")],
+                        raw_requires_post=Value(
+                            tokens=[
+                                Token(value="Eq"),
+                                Token(value="<"),
+                                Token(value="T"),
+                                Token(value=">"),
+                            ]
+                        ),
+                    ),
+                )
+            ]
+        )
+    )
+
+
+def test_requires_first_elem1() -> None:
+    content = """
+      template<typename T> requires Addable<T> // or right after a template parameter list
+      T add(T a, T b) { return a + b; }
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[NameSpecifier(name="T")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="add")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="a",
+                        ),
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="b",
+                        ),
+                    ],
+                    has_body=True,
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="typename", name="T")],
+                        raw_requires_pre=Value(
+                            tokens=[
+                                Token(value="Addable"),
+                                Token(value="<"),
+                                Token(value="T"),
+                                Token(value=">"),
+                            ]
+                        ),
+                    ),
+                )
+            ]
+        )
+    )
+
+
+def test_requires_first_elem2() -> None:
+    content = """
+      template<typename T> requires std::is_arithmetic_v<T>
+      T add(T a, T b) { return a + b; }
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[NameSpecifier(name="T")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="add")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="a",
+                        ),
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="b",
+                        ),
+                    ],
+                    has_body=True,
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="typename", name="T")],
+                        raw_requires_pre=Value(
+                            tokens=[
+                                Token(value="std"),
+                                Token(value="is_arithmetic_v"),
+                                Token(value="<"),
+                                Token(value="T"),
+                                Token(value=">"),
+                            ]
+                        ),
+                    ),
+                )
+            ]
+        )
+    )
+
+
+def test_requires_compound() -> None:
+    content = """
+      template<typename T> requires Addable<T> || Subtractable<T>
+      T add(T a, T b) { return a + b; }
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[NameSpecifier(name="T")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="add")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="a",
+                        ),
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="b",
+                        ),
+                    ],
+                    has_body=True,
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="typename", name="T")],
+                        raw_requires_pre=Value(
+                            tokens=[
+                                Token(value="Addable"),
+                                Token(value="<"),
+                                Token(value="T"),
+                                Token(value=">"),
+                                Token(value="||"),
+                                Token(value="Subtractable"),
+                                Token(value="<"),
+                                Token(value="T"),
+                                Token(value=">"),
+                            ]
+                        ),
+                    ),
+                )
+            ]
+        )
+    )
+
+
+def test_requires_ad_hoc() -> None:
+    content = """
+      template<typename T>
+          requires requires (T x) { x + x; } // ad-hoc constraint, note keyword used twice
+      T add(T a, T b) { return a + b; }
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[NameSpecifier(name="T")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="add")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="a",
+                        ),
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="b",
+                        ),
+                    ],
+                    has_body=True,
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="typename", name="T")],
+                        raw_requires_pre=Value(
+                            tokens=[
+                                Token(value="requires"),
+                                Token(value="("),
+                                Token(value="T"),
+                                Token(value="x"),
+                                Token(value=")"),
+                                Token(value="{"),
+                                Token(value="x"),
+                                Token(value="+"),
+                                Token(value="x"),
+                                Token(value=";"),
+                                Token(value="}"),
+                            ]
+                        ),
+                    ),
+                )
+            ]
+        )
+    )
+
+
+def test_requires_both() -> None:
+    content = """
+      // clang-format off
+      template<typename T>
+      requires Addable<T>
+      auto f1(T a, T b) requires Subtractable<T>;
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(typename=PQName(segments=[AutoSpecifier()])),
+                    name=PQName(segments=[NameSpecifier(name="f1")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="a",
+                        ),
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            ),
+                            name="b",
+                        ),
+                    ],
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="typename", name="T")],
+                        raw_requires_pre=Value(
+                            tokens=[
+                                Token(value="Addable"),
+                                Token(value="<"),
+                                Token(value="T"),
+                                Token(value=">"),
+                            ]
+                        ),
+                        raw_requires_post=Value(
+                            tokens=[
+                                Token(value="Subtractable"),
+                                Token(value="<"),
+                                Token(value="T"),
+                                Token(value=">"),
+                            ]
+                        ),
+                    ),
+                )
+            ]
+        )
+    )
+
+
+def test_requires_paren() -> None:
+    content = """
+      // clang-format off
+      template<class T>
+      void h(T) requires (is_purrable<T>());
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            functions=[
+                Function(
+                    return_type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="void")])
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="h")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(segments=[NameSpecifier(name="T")])
+                            )
+                        )
+                    ],
+                    template=TemplateDecl(
+                        params=[TemplateTypeParam(typekey="class", name="T")],
+                        raw_requires_post=Value(
+                            tokens=[
+                                Token(value="("),
+                                Token(value="is_purrable"),
+                                Token(value="<"),
+                                Token(value="T"),
+                                Token(value=">"),
+                                Token(value="("),
+                                Token(value=")"),
+                                Token(value=")"),
+                            ]
+                        ),
+                    ),
+                )
+            ]
+        )
+    )

tests/test_preprocessor.py

@@ -1,9 +1,20 @@
 import os
 import pathlib
+import pytest
+import re
+import shutil
+import subprocess
+import typing
 
-from cxxheaderparser.options import ParserOptions
-from cxxheaderparser.preprocessor import make_pcpp_preprocessor
-from cxxheaderparser.simple import NamespaceScope, ParsedData, parse_file, parse_string
+from cxxheaderparser.options import ParserOptions, PreprocessorFunction
+from cxxheaderparser import preprocessor
+from cxxheaderparser.simple import (
+    NamespaceScope,
+    ParsedData,
+    parse_file,
+    parse_string,
+    Include,
+)
 from cxxheaderparser.types import (
     FundamentalSpecifier,
     NameSpecifier,
@@ -15,12 +26,39 @@ from cxxheaderparser.types import (
 )
 
 
-def test_basic_preprocessor() -> None:
+@pytest.fixture(params=["gcc", "msvc", "pcpp"])
+def make_pp(request) -> typing.Callable[..., PreprocessorFunction]:
+    param = request.param
+    if param == "gcc":
+        gcc_path = shutil.which("g++")
+        if not gcc_path:
+            pytest.skip("g++ not found")
+
+        subprocess.run([gcc_path, "--version"])
+        return preprocessor.make_gcc_preprocessor
+    elif param == "msvc":
+        gcc_path = shutil.which("cl.exe")
+        if not gcc_path:
+            pytest.skip("cl.exe not found")
+
+        return preprocessor.make_msvc_preprocessor
+    elif param == "pcpp":
+        if preprocessor.pcpp is None:
+            pytest.skip("pcpp not installed")
+        return preprocessor.make_pcpp_preprocessor
+    else:
+        assert False
+
+
+def test_basic_preprocessor(
+    make_pp: typing.Callable[..., PreprocessorFunction]
+) -> None:
     content = """
       #define X 1
       int x = X;
     """
-    options = ParserOptions(preprocessor=make_pcpp_preprocessor())
+
+    options = ParserOptions(preprocessor=make_pp())
     data = parse_string(content, cleandoc=True, options=options)
 
     assert data == ParsedData(
@@ -38,7 +76,10 @@ def test_basic_preprocessor() -> None:
     )
 
 
-def test_preprocessor_omit_content(tmp_path: pathlib.Path) -> None:
+def test_preprocessor_omit_content(
+    make_pp: typing.Callable[..., PreprocessorFunction],
+    tmp_path: pathlib.Path,
+) -> None:
     """Ensure that content in other headers is omitted"""
     h_content = '#include "t2.h"' "\n" "int x = X;\n"
     h2_content = "#define X 2\n" "int omitted = 1;\n"
@@ -49,7 +90,7 @@ def test_preprocessor_omit_content(tmp_path: pathlib.Path) -> None:
     with open(tmp_path / "t2.h", "w") as fp:
         fp.write(h2_content)
 
-    options = ParserOptions(preprocessor=make_pcpp_preprocessor())
+    options = ParserOptions(preprocessor=make_pp())
     data = parse_file(tmp_path / "t1.h", options=options)
 
     assert data == ParsedData(
@@ -67,7 +108,10 @@ def test_preprocessor_omit_content(tmp_path: pathlib.Path) -> None:
     )
 
 
-def test_preprocessor_omit_content2(tmp_path: pathlib.Path) -> None:
+def test_preprocessor_omit_content2(
+    make_pp: typing.Callable[..., PreprocessorFunction],
+    tmp_path: pathlib.Path,
+) -> None:
     """
     Ensure that content in other headers is omitted while handling pcpp
     relative path quirk
@@ -84,9 +128,7 @@ def test_preprocessor_omit_content2(tmp_path: pathlib.Path) -> None:
     with open(tmp_path2 / "t2.h", "w") as fp:
         fp.write(h2_content)
 
-    options = ParserOptions(
-        preprocessor=make_pcpp_preprocessor(include_paths=[str(tmp_path)])
-    )
+    options = ParserOptions(preprocessor=make_pp(include_paths=[str(tmp_path)]))
 
     # Weirdness happens here
     os.chdir(tmp_path)
@@ -107,7 +149,9 @@ def test_preprocessor_omit_content2(tmp_path: pathlib.Path) -> None:
     )
 
 
-def test_preprocessor_encoding(tmp_path: pathlib.Path) -> None:
+def test_preprocessor_encoding(
+    make_pp: typing.Callable[..., PreprocessorFunction], tmp_path: pathlib.Path
+) -> None:
     """Ensure we can handle alternate encodings"""
     h_content = b"// \xa9 2023 someone\n" b'#include "t2.h"' b"\n" b"int x = X;\n"
 
@@ -119,7 +163,7 @@ def test_preprocessor_encoding(tmp_path: pathlib.Path) -> None:
     with open(tmp_path / "t2.h", "wb") as fp:
         fp.write(h2_content)
 
-    options = ParserOptions(preprocessor=make_pcpp_preprocessor(encoding="cp1252"))
+    options = ParserOptions(preprocessor=make_pp(encoding="cp1252"))
     data = parse_file(tmp_path / "t1.h", options=options, encoding="cp1252")
 
     assert data == ParsedData(
@@ -135,3 +179,26 @@ def test_preprocessor_encoding(tmp_path: pathlib.Path) -> None:
             ]
         )
     )
+
+
+@pytest.mark.skipif(preprocessor.pcpp is None, reason="pcpp not installed")
+def test_preprocessor_passthru_includes(tmp_path: pathlib.Path) -> None:
+    """Ensure that all #include pass through"""
+    h_content = '#include "t2.h"\n'
+
+    with open(tmp_path / "t1.h", "w") as fp:
+        fp.write(h_content)
+
+    with open(tmp_path / "t2.h", "w") as fp:
+        fp.write("")
+
+    options = ParserOptions(
+        preprocessor=preprocessor.make_pcpp_preprocessor(
+            passthru_includes=re.compile(".+")
+        )
+    )
+    data = parse_file(tmp_path / "t1.h", options=options)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(), includes=[Include(filename='"t2.h"')]
+    )