[Clang] Add the template depth when parsing type constraints

clang/docs/ReleaseNotes.rst

@@ -469,6 +469,7 @@ 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

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 increase
+  // the template depth as these parameters would not be instantiated
+  // at the current level.
+  TemplateParameterDepthRAII CurTemplateDepthTracker(TemplateParameterDepth);
+  ++CurTemplateDepthTracker;
   CXXScopeSpec SS;
   bool WasScopeAnnotation = Tok.is(tok::annot_cxxscope);
   if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,

clang/test/SemaTemplate/concepts.cpp

@@ -1489,6 +1489,31 @@ 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 {};