[clang] Defer the instantiation of explicit-specifier until constraint checking completes (PR #70548)
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Sat Oct 28 03:36:45 PDT 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: 刘雨培 (LYP951018)
<details>
<summary>Changes</summary>
Modifications:
- Skipped the instantiation of the explicit-specifier during Decl substitution if we were deducing template arguments and the explicit-specifier was value dependent.
- Instantiated the explicit-specifier after the constraint checking completed.
- Made `instantiateExplicitSpecifier` a member function in order to instantiate the explicit-specifier in different stages.
This PR doesn’t defer the instantiation of the explicit specifier for deduction guides, because I’m not familiar with deduction guides yet. I’ll dig into it after this PR.
According to my local test, GCC 13 tuple works with this PR.
Fixes #<!-- -->59827.
---
Full diff: https://github.com/llvm/llvm-project/pull/70548.diff
5 Files Affected:
- (modified) clang/docs/ReleaseNotes.rst (+4)
- (modified) clang/include/clang/Sema/Sema.h (+3)
- (modified) clang/lib/Sema/SemaTemplateDeduction.cpp (+56)
- (modified) clang/lib/Sema/SemaTemplateInstantiateDecl.cpp (+26-14)
- (added) clang/test/SemaCXX/cxx2a-explicit-bool-deferred.cpp (+31)
``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 2595737e8b3b143..ad41a831477f66c 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -670,6 +670,10 @@ Bug Fixes to C++ Support
default initializing a base class in a constant expression context. Fixes:
(`#69890 <https://github.com/llvm/llvm-project/issues/69890>`_)
+- Clang now defers the instantiation of explicit specifier until constraint checking
+ completes (except deduction guides). Fixes:
+ (`#59827 <https://github.com/llvm/llvm-project/issues/59827>`_)
+
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed an import failure of recursive friend class template.
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 1e9752345ffd173..93fd6507db3d78a 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -10430,6 +10430,9 @@ class Sema final {
const CXXConstructorDecl *Tmpl,
const MultiLevelTemplateArgumentList &TemplateArgs);
+ ExplicitSpecifier instantiateExplicitSpecifier(
+ const MultiLevelTemplateArgumentList &TemplateArgs, ExplicitSpecifier ES);
+
NamedDecl *FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
const MultiLevelTemplateArgumentList &TemplateArgs,
bool FindingInstantiatedContext = false);
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 0b3f0247ea3bee3..e75e46aa5228812 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3553,6 +3553,53 @@ static unsigned getPackIndexForParam(Sema &S,
llvm_unreachable("parameter index would not be produced from template");
}
+// if `Specialization` is a `CXXConstructorDecl` or `CXXConversionDecl`
+// we try to instantiate and update its explicit specifier after constraint
+// checking.
+static Sema::TemplateDeductionResult
+tryInstantiateExplicitSpecifier(Sema &S, FunctionDecl *Specialization,
+ const MultiLevelTemplateArgumentList &SubstArgs,
+ TemplateDeductionInfo &Info,
+ FunctionTemplateDecl *FunctionTemplate,
+ ArrayRef<TemplateArgument> DeducedArgs) {
+
+ const auto TryInstantiateExplicitSpecifierForSingleDecl =
+ [&](auto *ExplicitDecl) {
+ ExplicitSpecifier ExplicitSpecifier =
+ ExplicitDecl->getExplicitSpecifier();
+ Expr *const Expr = ExplicitSpecifier.getExpr();
+ if (!Expr) {
+ return Sema::TDK_Success;
+ }
+ if (!Expr->isValueDependent()) {
+ return Sema::TDK_Success;
+ }
+ Sema::InstantiatingTemplate Inst(
+ S, Info.getLocation(), FunctionTemplate, DeducedArgs,
+ Sema::CodeSynthesisContext::DeducedTemplateArgumentSubstitution,
+ Info);
+ const auto Instantiated =
+ S.instantiateExplicitSpecifier(SubstArgs, ExplicitSpecifier);
+ if (Instantiated.isInvalid()) {
+ ExplicitDecl->setInvalidDecl(true);
+ return clang::Sema::TDK_SubstitutionFailure;
+ }
+ ExplicitDecl->setExplicitSpecifier(Instantiated);
+ return clang::Sema::TDK_Success;
+ };
+ Sema::TemplateDeductionResult DeductionResult = clang::Sema::TDK_Success;
+ if (CXXConstructorDecl *ConstructorDecl =
+ dyn_cast_or_null<CXXConstructorDecl>(Specialization)) {
+ DeductionResult =
+ TryInstantiateExplicitSpecifierForSingleDecl(ConstructorDecl);
+ } else if (CXXConversionDecl *ConversionDecl =
+ dyn_cast_or_null<CXXConversionDecl>(Specialization)) {
+ DeductionResult =
+ TryInstantiateExplicitSpecifierForSingleDecl(ConversionDecl);
+ }
+ return DeductionResult;
+}
+
/// Finish template argument deduction for a function template,
/// checking the deduced template arguments for completeness and forming
/// the function template specialization.
@@ -3682,6 +3729,15 @@ Sema::TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
}
}
+ // We skipped the instantiation of the explicit-specifier during subst the
+ // decl before. Now, we try to instantiate it back if the Specialization is a
+ // constructor or a conversion.
+ if (TDK_Success !=
+ tryInstantiateExplicitSpecifier(*this, Specialization, SubstArgs, Info,
+ FunctionTemplate, DeducedArgs)) {
+ return TDK_SubstitutionFailure;
+ }
+
if (OriginalCallArgs) {
// C++ [temp.deduct.call]p4:
// In general, the deduction process attempts to find template argument
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 78a7892a35a320b..163dbef03e80a4d 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -563,18 +563,16 @@ static void instantiateDependentAMDGPUFlatWorkGroupSizeAttr(
S.addAMDGPUFlatWorkGroupSizeAttr(New, Attr, MinExpr, MaxExpr);
}
-static ExplicitSpecifier
-instantiateExplicitSpecifier(Sema &S,
- const MultiLevelTemplateArgumentList &TemplateArgs,
- ExplicitSpecifier ES, FunctionDecl *New) {
+ExplicitSpecifier Sema::instantiateExplicitSpecifier(
+ const MultiLevelTemplateArgumentList &TemplateArgs, ExplicitSpecifier ES) {
if (!ES.getExpr())
return ES;
Expr *OldCond = ES.getExpr();
Expr *Cond = nullptr;
{
EnterExpressionEvaluationContext Unevaluated(
- S, Sema::ExpressionEvaluationContext::ConstantEvaluated);
- ExprResult SubstResult = S.SubstExpr(OldCond, TemplateArgs);
+ *this, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+ ExprResult SubstResult = SubstExpr(OldCond, TemplateArgs);
if (SubstResult.isInvalid()) {
return ExplicitSpecifier::Invalid();
}
@@ -582,7 +580,7 @@ instantiateExplicitSpecifier(Sema &S,
}
ExplicitSpecifier Result(Cond, ES.getKind());
if (!Cond->isTypeDependent())
- S.tryResolveExplicitSpecifier(Result);
+ tryResolveExplicitSpecifier(Result);
return Result;
}
@@ -2073,8 +2071,8 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(
ExplicitSpecifier InstantiatedExplicitSpecifier;
if (auto *DGuide = dyn_cast<CXXDeductionGuideDecl>(D)) {
- InstantiatedExplicitSpecifier = instantiateExplicitSpecifier(
- SemaRef, TemplateArgs, DGuide->getExplicitSpecifier(), DGuide);
+ InstantiatedExplicitSpecifier = SemaRef.instantiateExplicitSpecifier(
+ TemplateArgs, DGuide->getExplicitSpecifier());
if (InstantiatedExplicitSpecifier.isInvalid())
return nullptr;
}
@@ -2453,11 +2451,25 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
}
}
- ExplicitSpecifier InstantiatedExplicitSpecifier =
- instantiateExplicitSpecifier(SemaRef, TemplateArgs,
- ExplicitSpecifier::getFromDecl(D), D);
- if (InstantiatedExplicitSpecifier.isInvalid())
- return nullptr;
+ auto InstantiatedExplicitSpecifier = ExplicitSpecifier::getFromDecl(D);
+ // deduction guides need this
+ const bool CouldInstantiate =
+ InstantiatedExplicitSpecifier.getExpr() == nullptr ||
+ !InstantiatedExplicitSpecifier.getExpr()->isValueDependent();
+
+ // Delay the instantiation of the explicit-specifier until after the
+ // constraints are checked during template argument deduction.
+ if (CouldInstantiate ||
+ SemaRef.CodeSynthesisContexts.back().Kind !=
+ Sema::CodeSynthesisContext::DeducedTemplateArgumentSubstitution) {
+ InstantiatedExplicitSpecifier = SemaRef.instantiateExplicitSpecifier(
+ TemplateArgs, InstantiatedExplicitSpecifier);
+
+ if (InstantiatedExplicitSpecifier.isInvalid())
+ return nullptr;
+ } else {
+ InstantiatedExplicitSpecifier.setKind(ExplicitSpecKind::Unresolved);
+ }
// Implicit destructors/constructors created for local classes in
// DeclareImplicit* (see SemaDeclCXX.cpp) might not have an associated TSI.
diff --git a/clang/test/SemaCXX/cxx2a-explicit-bool-deferred.cpp b/clang/test/SemaCXX/cxx2a-explicit-bool-deferred.cpp
new file mode 100644
index 000000000000000..4d667008f2e2763
--- /dev/null
+++ b/clang/test/SemaCXX/cxx2a-explicit-bool-deferred.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2a %s
+
+template <typename T1, typename T2> struct is_same {
+ static constexpr bool value = false;
+};
+
+template <typename T> struct is_same<T, T> {
+ static constexpr bool value = true;
+};
+
+template <class T, class U>
+concept SameHelper = is_same<T, U>::value;
+template <class T, class U>
+concept same_as = SameHelper<T, U> && SameHelper<U, T>;
+
+namespace deferred_instantiation {
+template <class X> constexpr X do_not_instantiate() { return nullptr; }
+
+struct T {
+ template <same_as<float> X> explicit(do_not_instantiate<X>()) T(X) {}
+
+ T(int) {}
+};
+
+T t(5);
+// expected-error at 17{{cannot initialize}}
+// expected-note at 20{{in instantiation of function template specialization}}
+// expected-note at 30{{while substituting deduced template arguments}}
+// expected-note at 30{{in instantiation of function template specialization}}
+T t2(5.0f);
+} // namespace deferred_instantiation
``````````
</details>
https://github.com/llvm/llvm-project/pull/70548
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