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Per CWG 2672 substitution failure within the body of a lambda inside a
requires-expression should be a hard error.
Fixes https://github.com/llvm/llvm-project/issues/64138
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D156993
Files:
clang/docs/ReleaseNotes.rst
clang/lib/Sema/SemaTemplateInstantiate.cpp
clang/test/SemaCXX/lambda-unevaluated.cpp
Index: clang/test/SemaCXX/lambda-unevaluated.cpp
===================================================================
--- clang/test/SemaCXX/lambda-unevaluated.cpp
+++ clang/test/SemaCXX/lambda-unevaluated.cpp
@@ -155,17 +155,24 @@
template <class T>
concept lambda_works = requires {
- []() { T::foo(); };
+ []() { T::foo(); }; // expected-error{{type 'int' cannot be used prior to
'::'}}
+ // expected-note@-1{{while substituting into a lambda
expression here}}
+ // expected-note@-2{{in instantiation of requirement
here}}
+ // expected-note@-4{{while substituting template
arguments into constraint expression here}}
};
-static_assert(!lambda_works<int>);
+static_assert(!lambda_works<int>); // expected-note {{while checking the
satisfaction of concept 'lambda_works<int>' requested here}}
static_assert(lambda_works<WithFoo>);
template <class T>
-int* func(T) requires requires { []() { T::foo(); }; };
+int* func(T) requires requires { []() { T::foo(); }; }; //
expected-error{{type 'int' cannot be used prior to '::'}}
+ //
expected-note@-1{{while substituting into a lambda expression here}}
+ //
expected-note@-2{{in instantiation of requirement here}}
+ //
expected-note@-3{{while substituting template arguments into constraint
expression here}}
double* func(...);
-static_assert(__is_same(decltype(func(0)), double*));
+static_assert(__is_same(decltype(func(0)), double*)); // expected-note {{while
checking constraint satisfaction for template 'func<int>' required here}}
+ // expected-note@-1 {{in
instantiation of function template specialization
'lambda_in_constraints::func<int>'}}
static_assert(__is_same(decltype(func(WithFoo())), int*));
template <class T>
Index: clang/lib/Sema/SemaTemplateInstantiate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1074,7 +1074,6 @@
if (InNonInstantiationSFINAEContext)
return std::optional<TemplateDeductionInfo *>(nullptr);
- bool SawLambdaSubstitution = false;
for (SmallVectorImpl<CodeSynthesisContext>::const_reverse_iterator
Active = CodeSynthesisContexts.rbegin(),
ActiveEnd = CodeSynthesisContexts.rend();
@@ -1101,10 +1100,7 @@
// A lambda-expression appearing in a function type or a template
// parameter is not considered part of the immediate context for the
// purposes of template argument deduction.
-
- // We need to check parents.
- SawLambdaSubstitution = true;
- break;
+ return std::nullopt;
case CodeSynthesisContext::DefaultTemplateArgumentInstantiation:
case CodeSynthesisContext::PriorTemplateArgumentSubstitution:
@@ -1120,8 +1116,6 @@
// We're either substituting explicitly-specified template arguments,
// deduced template arguments. SFINAE applies unless we are in a lambda
// expression, see [temp.deduct]p9.
- if (SawLambdaSubstitution)
- return std::nullopt;
[[fallthrough]];
case CodeSynthesisContext::ConstraintSubstitution:
case CodeSynthesisContext::RequirementInstantiation:
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -132,6 +132,10 @@
(`#35574 <https://github.com/llvm/llvm-project/issues/35574>_`) and
(`#27224 <https://github.com/llvm/llvm-project/issues/27224>_`).
+- Clang emits an error on substitution failure within lambda body inside a
+ requires-expression. This fixes:
+ (`#64138 <https://github.com/llvm/llvm-project/issues/64138>_`).
+
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed an import failure of recursive friend class template.
Index: clang/test/SemaCXX/lambda-unevaluated.cpp
===================================================================
--- clang/test/SemaCXX/lambda-unevaluated.cpp
+++ clang/test/SemaCXX/lambda-unevaluated.cpp
@@ -155,17 +155,24 @@
template <class T>
concept lambda_works = requires {
- []() { T::foo(); };
+ []() { T::foo(); }; // expected-error{{type 'int' cannot be used prior to '::'}}
+ // expected-note@-1{{while substituting into a lambda expression here}}
+ // expected-note@-2{{in instantiation of requirement here}}
+ // expected-note@-4{{while substituting template arguments into constraint expression here}}
};
-static_assert(!lambda_works<int>);
+static_assert(!lambda_works<int>); // expected-note {{while checking the satisfaction of concept 'lambda_works<int>' requested here}}
static_assert(lambda_works<WithFoo>);
template <class T>
-int* func(T) requires requires { []() { T::foo(); }; };
+int* func(T) requires requires { []() { T::foo(); }; }; // expected-error{{type 'int' cannot be used prior to '::'}}
+ // expected-note@-1{{while substituting into a lambda expression here}}
+ // expected-note@-2{{in instantiation of requirement here}}
+ // expected-note@-3{{while substituting template arguments into constraint expression here}}
double* func(...);
-static_assert(__is_same(decltype(func(0)), double*));
+static_assert(__is_same(decltype(func(0)), double*)); // expected-note {{while checking constraint satisfaction for template 'func<int>' required here}}
+ // expected-note@-1 {{in instantiation of function template specialization 'lambda_in_constraints::func<int>'}}
static_assert(__is_same(decltype(func(WithFoo())), int*));
template <class T>
Index: clang/lib/Sema/SemaTemplateInstantiate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1074,7 +1074,6 @@
if (InNonInstantiationSFINAEContext)
return std::optional<TemplateDeductionInfo *>(nullptr);
- bool SawLambdaSubstitution = false;
for (SmallVectorImpl<CodeSynthesisContext>::const_reverse_iterator
Active = CodeSynthesisContexts.rbegin(),
ActiveEnd = CodeSynthesisContexts.rend();
@@ -1101,10 +1100,7 @@
// A lambda-expression appearing in a function type or a template
// parameter is not considered part of the immediate context for the
// purposes of template argument deduction.
-
- // We need to check parents.
- SawLambdaSubstitution = true;
- break;
+ return std::nullopt;
case CodeSynthesisContext::DefaultTemplateArgumentInstantiation:
case CodeSynthesisContext::PriorTemplateArgumentSubstitution:
@@ -1120,8 +1116,6 @@
// We're either substituting explicitly-specified template arguments,
// deduced template arguments. SFINAE applies unless we are in a lambda
// expression, see [temp.deduct]p9.
- if (SawLambdaSubstitution)
- return std::nullopt;
[[fallthrough]];
case CodeSynthesisContext::ConstraintSubstitution:
case CodeSynthesisContext::RequirementInstantiation:
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -132,6 +132,10 @@
(`#35574 <https://github.com/llvm/llvm-project/issues/35574>_`) and
(`#27224 <https://github.com/llvm/llvm-project/issues/27224>_`).
+- Clang emits an error on substitution failure within lambda body inside a
+ requires-expression. This fixes:
+ (`#64138 <https://github.com/llvm/llvm-project/issues/64138>_`).
+
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed an import failure of recursive friend class template.
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