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Declaration context of template parameters of a FunctionTemplateDecl
may be different for each one parameter if the template is a
deduction guide. This case is handled correctly after this change.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D114418
Files:
clang/include/clang/AST/ASTImporterLookupTable.h
clang/lib/AST/ASTImporter.cpp
clang/lib/AST/ASTImporterLookupTable.cpp
clang/unittests/AST/ASTImporterTest.cpp
Index: clang/unittests/AST/ASTImporterTest.cpp
===================================================================
--- clang/unittests/AST/ASTImporterTest.cpp
+++ clang/unittests/AST/ASTImporterTest.cpp
@@ -7329,6 +7329,34 @@
EXPECT_EQ(*ShadowI, ToUsingShadowF2);
}
+AST_MATCHER_P(FunctionTemplateDecl, templateParameterCountIs, unsigned, Cnt) {
+ return Node.getTemplateParameters()->size() == Cnt;
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, ImportDeductionGuide) {
+ TranslationUnitDecl *FromTU = getTuDecl(
+ R"(
+ template<class> class A { };
+ template<class T> class B {
+ template<class T1, typename = A<T>> B(T1);
+ };
+ template<class T>
+ B(T, T) -> B<int>;
+ )",
+ Lang_CXX17);
+
+ // Get the implicit deduction guide for (non-default) constructor of 'B'.
+ auto *FromDG1 = FirstDeclMatcher<FunctionTemplateDecl>().match(
+ FromTU, functionTemplateDecl(templateParameterCountIs(3)));
+ // User defined deduction guide.
+ auto *FromDG2 = FirstDeclMatcher<CXXDeductionGuideDecl>().match(
+ FromTU, cxxDeductionGuideDecl(unless(isImplicit())));
+
+ // Check if the import does not crash.
+ (void)Import(FromDG1, Lang_CXX17);
+ (void)Import(FromDG2, Lang_CXX17);
+}
+
INSTANTIATE_TEST_SUITE_P(ParameterizedTests, ASTImporterLookupTableTest,
DefaultTestValuesForRunOptions);
Index: clang/lib/AST/ASTImporterLookupTable.cpp
===================================================================
--- clang/lib/AST/ASTImporterLookupTable.cpp
+++ clang/lib/AST/ASTImporterLookupTable.cpp
@@ -140,6 +140,11 @@
add(ND);
}
+void ASTImporterLookupTable::updateForced(NamedDecl *ND, DeclContext *OldDC) {
+ LookupTable[OldDC][ND->getDeclName()].remove(ND);
+ add(ND);
+}
+
ASTImporterLookupTable::LookupResult
ASTImporterLookupTable::lookup(DeclContext *DC, DeclarationName Name) const {
auto DCI = LookupTable.find(DC->getPrimaryContext());
Index: clang/lib/AST/ASTImporter.cpp
===================================================================
--- clang/lib/AST/ASTImporter.cpp
+++ clang/lib/AST/ASTImporter.cpp
@@ -6066,20 +6066,27 @@
if (Error Err = importInto(TemplatedFD, D->getTemplatedDecl()))
return std::move(Err);
- // Template parameters of the ClassTemplateDecl and FunctionTemplateDecl are
- // shared, if the FunctionTemplateDecl is a deduction guide for the class.
- // At import the ClassTemplateDecl object is always created first (FIXME: is
- // this really true?) because the dependency, then the FunctionTemplateDecl.
- // The DeclContext of the template parameters is changed when the
- // FunctionTemplateDecl is created, but was set already when the class
- // template was created. So here it is not the TU (default value) any more.
- // FIXME: The DeclContext of the parameters is now set finally to the
- // CXXDeductionGuideDecl object that was imported later. This may not be the
- // same that is in the original AST, specially if there are multiple deduction
- // guides.
- DeclContext *OldParamDC = nullptr;
- if (Params->size() > 0)
- OldParamDC = Params->getParam(0)->getDeclContext();
+ // At creation of the template the template parameters are "adopted"
+ // (DeclContext is changed). After this possible change the lookup table
+ // must be updated.
+ // At deduction guides the DeclContext of the template parameters may be
+ // different from what we would expect, it may be the class template, or a
+ // probably different CXXDeductionGuideDecl. This may come from the fact that
+ // the template parameter objects may be shared between deduction guides or
+ // the class template, and at creation of multiple FunctionTemplateDecl
+ // objects (for deduction guides) the same parameters are re-used. The
+ // "adoption" happens multiple times with different parent, even recursively
+ // for TemplateTemplateParmDecl. The same happens at import when the
+ // FunctionTemplateDecl objects are created, but in different order. In this
+ // way DeclContext of these template parameters may change relative to the
+ // "from" context. Because these DeclContext values look already not stable
+ // and unimportant this change looks acceptable.
+ // For these reasons the old DeclContext must be saved to change the lookup
+ // table later.
+ SmallVector<DeclContext *, 2> OldParamDC;
+ OldParamDC.reserve(Params->size());
+ llvm::transform(*Params, std::back_inserter(OldParamDC),
+ [](NamedDecl *ND) { return ND->getDeclContext(); });
FunctionTemplateDecl *ToFunc;
if (GetImportedOrCreateDecl(ToFunc, D, Importer.getToContext(), DC, Loc, Name,
@@ -6091,7 +6098,12 @@
ToFunc->setAccess(D->getAccess());
ToFunc->setLexicalDeclContext(LexicalDC);
LexicalDC->addDeclInternal(ToFunc);
- updateLookupTableForTemplateParameters(*Params, OldParamDC);
+
+ ASTImporterLookupTable *LT = Importer.SharedState->getLookupTable();
+ if (LT && !OldParamDC.empty()) {
+ for (unsigned int I = 0; I < OldParamDC.size(); ++I)
+ LT->updateForced(Params->getParam(I), OldParamDC[I]);
+ }
if (FoundByLookup) {
auto *Recent =
Index: clang/include/clang/AST/ASTImporterLookupTable.h
===================================================================
--- clang/include/clang/AST/ASTImporterLookupTable.h
+++ clang/include/clang/AST/ASTImporterLookupTable.h
@@ -75,6 +75,10 @@
// The function should be called when the old context is definitely different
// from the new.
void update(NamedDecl *ND, DeclContext *OldDC);
+ // Same as 'update' but allow if 'ND' is not in the table or the old context
+ // is the same as the new.
+ // FIXME: The old redeclaration context is not handled.
+ void updateForced(NamedDecl *ND, DeclContext *OldDC);
using LookupResult = DeclList;
LookupResult lookup(DeclContext *DC, DeclarationName Name) const;
// Check if the `ND` is within the lookup table (with its current name) in
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