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Add support for cxx23 deducing-this. Fixes #120 #121

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Merged
merged 1 commit into from
Jul 14, 2025
Merged

Add support for cxx23 deducing-this. Fixes #120 #121

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43 changes: 35 additions & 8 deletions cxxheaderparser/parser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand Down Expand Up @@ -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]]:
"""
Expand All @@ -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 deduce_this_ok and self.lex.token_if("this"):
extras["deduces_this"] = True

if not tok:
tok = self.lex.token()
Expand Down Expand Up @@ -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
Expand All @@ -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(
Expand Down Expand Up @@ -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:
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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)
Expand Down
3 changes: 3 additions & 0 deletions cxxheaderparser/types.py
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Original file line number Diff line number Diff line change
Expand Up @@ -665,6 +665,9 @@ class Parameter:
default: typing.Optional[Value] = None
param_pack: bool = False

#: Indicates that this parameter is the parameter used for cxx23 deducing-this
deduces_this: bool = False

def format(self) -> str:
default = f" = {self.default.format()}" if self.default else ""
pp = "... " if self.param_pack else ""
Expand Down
54 changes: 54 additions & 0 deletions tests/test_class.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand Down