ilya-biryukov created this revision.
ilya-biryukov added reviewers: aaron.ballman, erichkeane.
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This commit implements [temp.deduct]p9.
Test updates include:
- New notes in `cxx1y-init-captures.cpp`, `lambda-expressions.cpp` and
'warn-unused-lambda-capture.cpp'. This seems to be caused by diagnosing errors
earlier (during deduction) that were previously surfaced later (during
instantiation).
- New error `lambda-unevaluated.cpp` is in line with [temp.deduct]p9.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D148802
Files:
clang/docs/ReleaseNotes.rst
clang/include/clang/Sema/Sema.h
clang/lib/Frontend/FrontendActions.cpp
clang/lib/Sema/SemaTemplateInstantiate.cpp
clang/test/CXX/temp/temp.deduct/p9.cpp
clang/test/SemaCXX/cxx1y-init-captures.cpp
clang/test/SemaCXX/lambda-expressions.cpp
clang/test/SemaCXX/lambda-unevaluated.cpp
clang/test/SemaCXX/warn-unused-lambda-capture.cpp
clang/www/cxx_status.html
Index: clang/www/cxx_status.html
===================================================================
--- clang/www/cxx_status.html
+++ clang/www/cxx_status.html
@@ -1024,11 +1024,7 @@
<tr>
<td>Lambdas in unevaluated contexts</td>
<td><a href="https://wg21.link/p0315r4";>P0315R4</a></td>
- <td class="partial" align="center">
- <details><summary>Partial</summary>
- temp.deduct/9 is not implemented yet.
- </details>
- </td>
+ <td class="full" align="center">Clang 17</td>
</tr>
<!-- Jacksonville papers -->
<tr>
Index: clang/test/SemaCXX/warn-unused-lambda-capture.cpp
===================================================================
--- clang/test/SemaCXX/warn-unused-lambda-capture.cpp
+++ clang/test/SemaCXX/warn-unused-lambda-capture.cpp
@@ -189,7 +189,7 @@
}
void test_use_template() {
- test_templated<int>(); // expected-note{{in instantiation of function template specialization 'test_templated<int>' requested here}}
+ test_templated<int>(); // expected-note 13{{in instantiation of function template specialization 'test_templated<int>' requested here}}
}
namespace pr35555 {
Index: clang/test/SemaCXX/lambda-unevaluated.cpp
===================================================================
--- clang/test/SemaCXX/lambda-unevaluated.cpp
+++ clang/test/SemaCXX/lambda-unevaluated.cpp
@@ -28,8 +28,10 @@
template <class T>
auto g(T) -> decltype([]() { T::invalid; } ());
-auto e = g(0); // expected-error{{no matching function for call}}
-// expected-note@-2 {{substitution failure}}
+auto e = g(0); // expected-error@-1{{type 'int' cannot be used prior to '::'}}
+ // expected-note@-1{{while substituting deduced template}}
+ // expected-error@-2 {{no matching function for call to 'g'}}
+ // expected-note@-4 {{substitution failure}}
template <typename T>
auto foo(decltype([] {
@@ -146,3 +148,34 @@
namespace lambda_in_trailing_decltype {
auto x = ([](auto) -> decltype([] {}()) {}(0), 2);
}
+
+namespace lambda_in_constraints {
+struct WithFoo { static void foo(); };
+
+template <class T>
+concept lambda_works = requires {
+ []() { T::foo(); };
+};
+
+static_assert(!lambda_works<int>);
+static_assert(lambda_works<WithFoo>);
+
+template <class T>
+int* func(T) requires requires { []() { T::foo(); }; };
+double* func(...);
+
+static_assert(__is_same(decltype(func(0)), double*));
+static_assert(__is_same(decltype(func(WithFoo())), int*));
+
+template <class T>
+auto direct_lambda(T) -> decltype([] { T::foo(); }) {}
+void direct_lambda(...) {}
+
+void recursive() {
+ direct_lambda(0); // expected-error@-4 {{type 'int' cannot be used prior to '::'}}
+ // expected-note@-1 {{while substituting deduced template arguments}}
+ bool x = requires { direct_lambda(0); }; // expected-error@-6 {{type 'int' cannot be used prior to '::'}}
+ // expected-note@-1 {{while substituting deduced template arguments}}
+
+}
+}
Index: clang/test/SemaCXX/lambda-expressions.cpp
===================================================================
--- clang/test/SemaCXX/lambda-expressions.cpp
+++ clang/test/SemaCXX/lambda-expressions.cpp
@@ -263,7 +263,7 @@
// expected-note 4 {{capture 'ts' by}}
}
template void nested2(int); // ok
- template void nested2(int, int); // expected-note {{in instantiation of}}
+ template void nested2(int, int); // expected-note 2 {{in instantiation of}}
}
namespace PR13860 {
Index: clang/test/SemaCXX/cxx1y-init-captures.cpp
===================================================================
--- clang/test/SemaCXX/cxx1y-init-captures.cpp
+++ clang/test/SemaCXX/cxx1y-init-captures.cpp
@@ -31,7 +31,7 @@
}
- void h(int i, char c) { g(i, c); } //expected-note{{in instantiation}}
+ void h(int i, char c) { g(i, c); } //expected-note 2{{in instantiation}}
}
namespace odr_use_within_init_capture {
@@ -164,7 +164,7 @@
return 0;
}
-int run = test(); //expected-note {{instantiation}}
+int run = test(); //expected-note 2 {{instantiation}}
}
Index: clang/test/CXX/temp/temp.deduct/p9.cpp
===================================================================
--- /dev/null
+++ clang/test/CXX/temp/temp.deduct/p9.cpp
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -std=c++20 -verify %s
+template <class T>
+auto f(T) -> decltype([]() { T::invalid; } ());
+void f(...);
+void test_f() {
+ f(0); // expected-error@-3 {{type 'int' cannot be used prior to '::'}}
+ // expected-note@-1 {{while substituting deduced template arguments}}
+}
+
+template <class T, unsigned = sizeof([]() { T::invalid; })>
+void g(T);
+void g(...);
+void test_g() {
+ g(0); // expected-error@-4 {{type 'int' cannot be used prior to '::'}}
+ // expected-note@-4 {{in instantiation of default argument}}
+ // expected-note@-2 {{while substituting deduced template arguments}}
+}
+
+template <class T>
+auto h(T) -> decltype([x = T::invalid]() { });
+void h(...);
+void test_h() {
+ h(0); // expected-error@-3 {{type 'int' cannot be used prior to '::'}}
+ // expected-note@-1 {{while substituting deduced template arguments}}
+}
+
+template <class T>
+auto i(T) -> decltype([]() -> typename T::invalid { });
+void i(...);
+void test_i() {
+ i(0); // expected-error@-3 {{type 'int' cannot be used prior to '::'}}
+ // expected-note@-1 {{while substituting deduced template arguments}}
+}
+
+template <class T>
+auto j(T t) -> decltype([](auto x) -> decltype(x.invalid) { } (t)); // #1
+void j(...); // #2
+void test_j() {
+ j(0);
+}
Index: clang/lib/Sema/SemaTemplateInstantiate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -34,6 +34,7 @@
#include "clang/Sema/Template.h"
#include "clang/Sema/TemplateDeduction.h"
#include "clang/Sema/TemplateInstCallback.h"
+#include "llvm/ADT/ScopeExit.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TimeProfiler.h"
#include <optional>
@@ -367,6 +368,7 @@
case InitializingStructuredBinding:
case MarkingClassDllexported:
case BuildingBuiltinDumpStructCall:
+ case LambdaExpressionSubstitution:
return false;
// This function should never be called when Kind's value is Memoization.
@@ -959,6 +961,8 @@
break;
case CodeSynthesisContext::Memoization:
+ case CodeSynthesisContext::LambdaExpressionSubstitution:
+ // FIXME: add a note for lambdas.
break;
case CodeSynthesisContext::ConstraintsCheck: {
@@ -1016,6 +1020,7 @@
if (InNonInstantiationSFINAEContext)
return std::optional<TemplateDeductionInfo *>(nullptr);
+ bool SawLambdaSubstitution = false;
for (SmallVectorImpl<CodeSynthesisContext>::const_reverse_iterator
Active = CodeSynthesisContexts.rbegin(),
ActiveEnd = CodeSynthesisContexts.rend();
@@ -1037,6 +1042,15 @@
case CodeSynthesisContext::NestedRequirementConstraintsCheck:
// This is a template instantiation, so there is no SFINAE.
return std::nullopt;
+ case CodeSynthesisContext::LambdaExpressionSubstitution:
+ // [temp.deduct]p9
+ // 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;
case CodeSynthesisContext::DefaultTemplateArgumentInstantiation:
case CodeSynthesisContext::PriorTemplateArgumentSubstitution:
@@ -1049,12 +1063,17 @@
case CodeSynthesisContext::ExplicitTemplateArgumentSubstitution:
case CodeSynthesisContext::DeducedTemplateArgumentSubstitution:
+ // 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:
case CodeSynthesisContext::RequirementParameterInstantiation:
- // We're either substituting explicitly-specified template arguments,
- // deduced template arguments, a constraint expression or a requirement
- // in a requires expression, so SFINAE applies.
+ // SFINAE always applies in a constraint expression or a requirement
+ // in a requires expression.
assert(Active->DeductionInfo && "Missing deduction info pointer");
return Active->DeductionInfo;
@@ -1343,6 +1362,14 @@
ExprResult TransformLambdaExpr(LambdaExpr *E) {
LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
Sema::ConstraintEvalRAII<TemplateInstantiator> RAII(*this);
+
+ Sema::CodeSynthesisContext C;
+ C.Kind = clang::Sema::CodeSynthesisContext::LambdaExpressionSubstitution;
+ C.PointOfInstantiation = E->getBeginLoc();
+ SemaRef.pushCodeSynthesisContext(C);
+ auto PopCtx =
+ llvm::make_scope_exit([this] { SemaRef.popCodeSynthesisContext(); });
+
ExprResult Result = inherited::TransformLambdaExpr(E);
if (Result.isInvalid())
return Result;
Index: clang/lib/Frontend/FrontendActions.cpp
===================================================================
--- clang/lib/Frontend/FrontendActions.cpp
+++ clang/lib/Frontend/FrontendActions.cpp
@@ -372,6 +372,8 @@
return "ExplicitTemplateArgumentSubstitution";
case CodeSynthesisContext::DeducedTemplateArgumentSubstitution:
return "DeducedTemplateArgumentSubstitution";
+ case CodeSynthesisContext::LambdaExpressionSubstitution:
+ return "LambdaExpressionSubstitution";
case CodeSynthesisContext::PriorTemplateArgumentSubstitution:
return "PriorTemplateArgumentSubstitution";
case CodeSynthesisContext::DefaultTemplateArgumentChecking:
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -9257,6 +9257,9 @@
/// a TemplateDecl.
DeducedTemplateArgumentSubstitution,
+ /// We are substituting into a lambda expression.
+ LambdaExpressionSubstitution,
+
/// We are substituting prior template arguments into a new
/// template parameter. The template parameter itself is either a
/// NonTypeTemplateParmDecl or a TemplateTemplateParmDecl.
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -153,6 +153,10 @@
- A new builtin type trait ``__is_trivially_equaltiy_comparable`` has been added,
which checks whether comparing two instances of a type is equivalent to
``memcmp(&lhs, &rhs, sizeof(T)) == 0``.
+- Clang now implements `[temp.deduct]p9`, subsitution failures inside lambdas from
+ unevaluated contexts will be surfaced as errors. They were previously handled as
+ SFINAE.
+
New Compiler Flags
------------------
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