[clang-tools-extra] a671e79 - [clang] Implement CWG2413 (implicit `typename` in conversion operators) (#195207)
via cfe-commits
cfe-commits at lists.llvm.org
Fri May 1 18:59:32 PDT 2026
Author: Victor Chernyakin
Date: 2026-05-01T18:59:27-07:00
New Revision: a671e795908c306d4dc234d4ab017e141bf3d06e
URL: https://github.com/llvm/llvm-project/commit/a671e795908c306d4dc234d4ab017e141bf3d06e
DIFF: https://github.com/llvm/llvm-project/commit/a671e795908c306d4dc234d4ab017e141bf3d06e.diff
LOG: [clang] Implement CWG2413 (implicit `typename` in conversion operators) (#195207)
Link: [CWG2413](https://wg21.link/cwg2413). This DR was resolved by
[P1787R6](https://wg21.link/P1787R6) by adding the following wording to
[[temp.res.general]/4](https://eel.is/c++draft/temp.res.general#4):
> A [type-only
context](https://eel.is/c++draft/temp.res.general#def:context,type-only)
is defined as follows: A qualified or unqualified name is said to be in
a type-only context if it is the terminal name of
> - ...
> - a [type-specifier](https://eel.is/c++draft/dcl.type.general#nt:type-specifier) of a
> - ...
> - [conversion-type-id](https://eel.is/c++draft/class.conv.fct#nt:conversion-type-id),
Towards #54150.
Added:
Modified:
clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp
clang/docs/ReleaseNotes.rst
clang/include/clang/Parse/Parser.h
clang/lib/Parse/ParseDecl.cpp
clang/test/CXX/drs/cwg24xx.cpp
clang/test/CXX/temp/temp.res/p4.cpp
clang/www/cxx_dr_status.html
Removed:
################################################################################
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp
index 77ef2b8622c93..33359fdc3f4bc 100644
--- a/clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp
@@ -34,7 +34,8 @@ void RedundantTypenameCheck::registerMatchers(MatchFinder *Finder) {
cxxMethodDecl(), hasParent(friendDecl()),
functionDecl(has(nestedNameSpecifier())),
cxxDeductionGuideDecl(hasDeclContext(recordDecl())))))))),
- // Match return types.
+ // Match return types. FIXME: CWG2413 made conversion operators
+ // an implicit typename context.
functionDecl(unless(cxxConversionDecl()))))),
hasParent(expr(anyOf(cxxNamedCastExpr(), cxxNewExpr()))));
Finder->addMatcher(
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6b66a4fa1a261..61140ee6e880e 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -158,6 +158,9 @@ C++17 Feature Support
Resolutions to C++ Defect Reports
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+- Clang now allows omitting ``typename`` before a template name in a
+ conversion operator, implementing `CWG2413 <https://wg21.link/cwg2413>`_.
+
C Language Changes
------------------
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index 2274ece3d1d0e..cec1dc99e90d8 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -1685,13 +1685,13 @@ class Parser : public CodeCompletionHandler {
case DeclSpecContext::DSC_alias_declaration:
case DeclSpecContext::DSC_template_param:
case DeclSpecContext::DSC_new:
+ case DeclSpecContext::DSC_conv_operator:
return ImplicitTypenameContext::Yes;
case DeclSpecContext::DSC_normal:
case DeclSpecContext::DSC_objc_method_result:
case DeclSpecContext::DSC_condition:
case DeclSpecContext::DSC_template_arg:
- case DeclSpecContext::DSC_conv_operator:
case DeclSpecContext::DSC_association:
return ImplicitTypenameContext::No;
}
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 434a1a8fcb223..06203ba8aa64c 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3365,11 +3365,8 @@ void Parser::ParseDeclarationSpecifiers(
// If we are in a operator context, convert it back into a type specifier
// context for better error handling later on.
- if (DSContext == DeclSpecContext::DSC_conv_operator) {
- // No implicit typename here.
- AllowImplicitTypename = ImplicitTypenameContext::No;
+ if (DSContext == DeclSpecContext::DSC_conv_operator)
DSContext = DeclSpecContext::DSC_type_specifier;
- }
bool EnteringContext = (DSContext == DeclSpecContext::DSC_class ||
DSContext == DeclSpecContext::DSC_top_level);
diff --git a/clang/test/CXX/drs/cwg24xx.cpp b/clang/test/CXX/drs/cwg24xx.cpp
index 0a6a05c125451..5d6ec58b4caef 100644
--- a/clang/test/CXX/drs/cwg24xx.cpp
+++ b/clang/test/CXX/drs/cwg24xx.cpp
@@ -1,13 +1,23 @@
-// RUN: %clang_cc1 -std=c++98 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,cxx98-14
-// RUN: %clang_cc1 -std=c++11 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,cxx98-14
-// RUN: %clang_cc1 -std=c++14 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,cxx98-14
-// RUN: %clang_cc1 -std=c++17 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,since-cxx17
+// RUN: %clang_cc1 -std=c++98 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,cxx98-14,cxx98-17
+// RUN: %clang_cc1 -std=c++11 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,cxx98-14,cxx98-17
+// RUN: %clang_cc1 -std=c++14 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,cxx98-14,cxx98-17
+// RUN: %clang_cc1 -std=c++17 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,since-cxx17,cxx98-17
// RUN: %clang_cc1 -std=c++20 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,since-cxx20,since-cxx17
// RUN: %clang_cc1 -std=c++23 -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,since-cxx20,since-cxx17
// RUN: %clang_cc1 -std=c++2c -fexceptions -fcxx-exceptions -pedantic-errors %s -verify-directives -verify=expected,since-cxx20,since-cxx17
// cwg2406 is in cwg2406.cpp
+namespace cwg2413 { // cwg2413: 23
+template <typename T>
+struct S {
+ operator T::R();
+ // cxx98-17-error at -1 {{missing 'typename' prior to dependent type name 'T::R' is a C++20 extension}}
+ void f() { operator T::R(); }
+ // cxx98-17-error at -1 {{missing 'typename' prior to dependent type name 'T::R' is a C++20 extension}}
+};
+} // namespace cwg2413
+
namespace cwg2428 { // cwg2428: 19
#if __cplusplus >= 202002L
template <typename>
diff --git a/clang/test/CXX/temp/temp.res/p4.cpp b/clang/test/CXX/temp/temp.res/p4.cpp
index 9dbdd235e925d..6ca609b58cf2c 100644
--- a/clang/test/CXX/temp/temp.res/p4.cpp
+++ b/clang/test/CXX/temp/temp.res/p4.cpp
@@ -157,8 +157,8 @@ template int Test<X>;
template<typename T> struct A {
enum E : T::type {}; // expected-error{{missing 'typename'}}
- operator T::type() {} // expected-error{{missing 'typename'}}
- void f() { this->operator T::type(); } // expected-error{{missing 'typename'}}
+ operator T::type() {}
+ void f() { this->operator T::type(); }
};
template<typename T>
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 9f3cd07ea8a4e..feef0c3770f64 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16684,7 +16684,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
<td>[<a href="https://wg21.link/temp.res">temp.res</a>]</td>
<td>CD6</td>
<td><TT>typename</TT> in <I>conversion-function-id</I>s</td>
- <td class="unknown" align="center">Unknown</td>
+ <td class="unreleased" align="center">Clang 23</td>
</tr>
<tr id="2414">
<td><a href="https://cplusplus.github.io/CWG/issues/2414.html">2414</a></td>
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