[clang] f37bdc2 - [Clang] Add the template depth when parsing type constraints (#163960)

[via cfe-commits]

Author: Younan Zhang
Date: 2025-10-18T05:05:24Z
New Revision: f37bdc24e6e647ce1744dd608718fd55430f8e3a

URL: https://github.com/llvm/llvm-project/commit/f37bdc24e6e647ce1744dd608718fd55430f8e3a
DIFF: https://github.com/llvm/llvm-project/commit/f37bdc24e6e647ce1744dd608718fd55430f8e3a.diff

LOG: [Clang] Add the template depth when parsing type constraints (#163960)

The lambdas can introduce new template parameters, and things would go
wrong if the new template parameters still lived in the depth of the
parent, when we evaluate the type constraints.

Fixes https://github.com/llvm/llvm-project/issues/162092

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/Parse/ParseTemplate.cpp
    clang/test/SemaTemplate/concepts.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8b4246880e927..903fb9f9e3cf9 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -478,6 +478,7 @@ Bug Fixes to C++ Support
 - Fix a crash when attempting to deduce a deduction guide from a non deducible template template parameter. (#130604)
 - Fix for clang incorrectly rejecting the default construction of a union with
   nontrivial member when another member has an initializer. (#GH81774)
+- Fixed a template depth issue when parsing lambdas inside a type constraint. (#GH162092)
 - Diagnose unresolved overload sets in non-dependent compound requirements. (#GH51246) (#GH97753)
 
 Bug Fixes to AST Handling

diff  --git a/clang/lib/Parse/ParseTemplate.cpp b/clang/lib/Parse/ParseTemplate.cpp
index dbc7cbc6cdc0c..330a9c6aea0c5 100644
--- a/clang/lib/Parse/ParseTemplate.cpp
+++ b/clang/lib/Parse/ParseTemplate.cpp
@@ -533,6 +533,12 @@ bool Parser::isTypeConstraintAnnotation() {
 bool Parser::TryAnnotateTypeConstraint() {
   if (!getLangOpts().CPlusPlus20)
     return false;
+  // The type constraint may declare template parameters, notably
+  // if it contains a generic lambda, so we need to increment
+  // the template depth as these parameters would not be instantiated
+  // at the current depth.
+  TemplateParameterDepthRAII CurTemplateDepthTracker(TemplateParameterDepth);
+  ++CurTemplateDepthTracker;
   CXXScopeSpec SS;
   bool WasScopeAnnotation = Tok.is(tok::annot_cxxscope);
   if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,

diff  --git a/clang/test/SemaTemplate/concepts.cpp b/clang/test/SemaTemplate/concepts.cpp
index aaa20f6240e76..a54bc02226058 100644
--- a/clang/test/SemaTemplate/concepts.cpp
+++ b/clang/test/SemaTemplate/concepts.cpp
@@ -1514,6 +1514,31 @@ static_assert( requires {{ &f } -> C;} ); // expected-error {{reference to overl
 
 }
 
+namespace GH162092 {
+
+template <typename T>
+struct vector;
+
+template <typename T, typename U>
+concept C = __is_same_as(T, U);
+
+template<class T, auto Cpt>
+concept generic_range_value = requires {
+    Cpt.template operator()<int>();
+};
+
+
+template<generic_range_value<[]<
+   C<int>
+   >() {}> T>
+void x() {}
+
+void foo() {
+  x<vector<int>>();
+}
+
+}
+
 namespace GH162770 {
   enum e {};
   template<e> struct s {};