Add support for cxx23 deducing-this. Fixes robotpy#120

Author: kdkavanagh

cxxheaderparser/parser.py

@@ -608,11 +608,19 @@ def _parse_template_decl(self) -> TemplateDecl:
                         param = self._parse_template_type_parameter(tok, None)
                     else:
                         param, _ = self._parse_parameter(
-                            ptok, TemplateNonTypeParam, False, ">"
+                            ptok,
+                            TemplateNonTypeParam,
+                            concept_ok=False,
+                            deduce_this_ok=False,
+                            end=">",
                         )
                 else:
                     param, _ = self._parse_parameter(
-                        tok, TemplateNonTypeParam, concept_ok=False, end=">"
+                        tok,
+                        TemplateNonTypeParam,
+                        concept_ok=False,
+                        deduce_this_ok=False,
+                        end=">",
                     )
 
                 params.append(param)
@@ -1761,6 +1769,7 @@ def _parse_parameter(
         tok: typing.Optional[LexToken],
         cls: typing.Type[PT],
         concept_ok: bool,
+        deduce_this_ok: bool,
         end: str = ")",
     ) -> typing.Tuple[PT, typing.Optional[Type]]:
         """
@@ -1775,6 +1784,10 @@ def _parse_parameter(
         param_pack = False
         parsed_type: typing.Optional[Type]
         at_type: typing.Optional[Type] = None
+        extras: typing.Dict[str, typing.Any] = {}
+
+        if self.lex.token_if("this") and deduce_this_ok:
+            extras["deduces_this"] = True
 
         if not tok:
             tok = self.lex.token()
@@ -1825,12 +1838,18 @@ def _parse_parameter(
         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)
+        param = cls(
+            type=dtype,
+            name=param_name,
+            default=default,
+            param_pack=param_pack,
+            **extras,
+        )
         self.debug_print("parameter: %s", param)
         return param, at_type
 
     def _parse_parameters(
-        self, concept_ok: bool
+        self, concept_ok: bool, deduce_this_ok: bool
     ) -> typing.Tuple[typing.List[Parameter], bool, typing.List[TemplateParam]]:
         """
         Consumes function parameters and returns them, and vararg if found, and
@@ -1854,7 +1873,13 @@ def _parse_parameters(
                 self._next_token_must_be(")")
                 break
 
-            param, at_type = self._parse_parameter(None, Parameter, concept_ok)
+            # Deduce-this only applicable for first function parameter
+            param, at_type = self._parse_parameter(
+                None,
+                Parameter,
+                concept_ok,
+                deduce_this_ok=deduce_this_ok and len(params) == 0,
+            )
             params.append(param)
             if at_type:
                 at_params.append(
@@ -2047,7 +2072,9 @@ def _parse_function(
         state.location = location
         is_class_block = isinstance(state, ClassBlockState)
 
-        params, vararg, at_params = self._parse_parameters(True)
+        params, vararg, at_params = self._parse_parameters(
+            True, deduce_this_ok=is_class_block
+        )
 
         # Promote abbreviated template parameters
         if at_params:
@@ -2243,7 +2270,7 @@ def _parse_cv_ptr_or_fn(
                     toks = self._consume_balanced_tokens(gtok)
                     self.lex.return_tokens(toks[1:-1])
 
-                fn_params, vararg, _ = self._parse_parameters(False)
+                fn_params, vararg, _ = self._parse_parameters(False, False)
 
                 assert not isinstance(dtype, FunctionType)
                 dtype = dtype_fn = FunctionType(dtype, fn_params, vararg)
@@ -2273,7 +2300,7 @@ def _parse_cv_ptr_or_fn(
                         assert not isinstance(dtype, FunctionType)
                         dtype = self._parse_array_type(aptok, dtype)
                     elif aptok.type == "(":
-                        fn_params, vararg, _ = self._parse_parameters(False)
+                        fn_params, vararg, _ = self._parse_parameters(False, False)
                         # the type we already have is the return type of the function pointer
 
                         assert not isinstance(dtype, FunctionType)

cxxheaderparser/types.py

@@ -664,6 +664,8 @@ class Parameter:
     name: typing.Optional[str] = None
     default: typing.Optional[Value] = None
     param_pack: bool = False
+    deduces_this: bool = False
+    """Indicates that this parameter is the parameter used for cxx23 deducing-this"""
 
     def format(self) -> str:
         default = f" = {self.default.format()}" if self.default else ""

tests/test_class.py

@@ -883,6 +883,60 @@ class StoneClass {
     )
 
 
+def test_class_fn_deduce_this() -> None:
+    content = """
+      class StoneClass {
+        template<typename Self>
+        int doSelf(this Self&& self);
+      };
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            classes=[
+                ClassScope(
+                    class_decl=ClassDecl(
+                        typename=PQName(
+                            segments=[NameSpecifier(name="StoneClass")],
+                            classkey="class",
+                        )
+                    ),
+                    methods=[
+                        Method(
+                            return_type=Type(
+                                typename=PQName(
+                                    segments=[FundamentalSpecifier(name="int")]
+                                )
+                            ),
+                            name=PQName(segments=[NameSpecifier(name="doSelf")]),
+                            parameters=[
+                                Parameter(
+                                    type=MoveReference(
+                                        moveref_to=Type(
+                                            typename=PQName(
+                                                segments=[NameSpecifier(name="Self")]
+                                            )
+                                        )
+                                    ),
+                                    name="self",
+                                    deduces_this=True,
+                                )
+                            ],
+                            template=TemplateDecl(
+                                params=[
+                                    TemplateTypeParam(typekey="typename", name="Self")
+                                ]
+                            ),
+                            access="private",
+                        ),
+                    ],
+                )
+            ]
+        )
+    )
+
+
 def test_class_fn_return_global_ns() -> None:
     content = """
       struct Avacado {