P0091R3: Improved syntactic checking of deduction-guides.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@294395 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 90 insertions, 1 deletions

diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 49cf8e15ed..1ae89ea89b 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -8033,13 +8033,102 @@ Decl *Sema::ActOnConversionDeclarator(CXXConversionDecl *Conversion) {
   return Conversion;
 }
 
+namespace {
+/// Utility class to accumulate and print a diagnostic listing the invalid
+/// specifier(s) on a declaration.
+struct BadSpecifierDiagnoser {
+  BadSpecifierDiagnoser(Sema &S, SourceLocation Loc, unsigned DiagID)
+      : S(S), Diagnostic(S.Diag(Loc, DiagID)) {}
+  ~BadSpecifierDiagnoser() {
+    Diagnostic << Specifiers;
+  }
+
+  template<typename T> void check(SourceLocation SpecLoc, T Spec) {
+    return check(SpecLoc, DeclSpec::getSpecifierName(Spec));
+  }
+  void check(SourceLocation SpecLoc, DeclSpec::TST Spec) {
+    return check(SpecLoc,
+                 DeclSpec::getSpecifierName(Spec, S.getPrintingPolicy()));
+  }
+  void check(SourceLocation SpecLoc, const char *Spec) {
+    if (SpecLoc.isInvalid()) return;
+    Diagnostic << SourceRange(SpecLoc, SpecLoc);
+    if (!Specifiers.empty()) Specifiers += " ";
+    Specifiers += Spec;
+  }
+
+  Sema &S;
+  Sema::SemaDiagnosticBuilder Diagnostic;
+  std::string Specifiers;
+};
+}
+
 /// Check the validity of a declarator that we parsed for a deduction-guide.
 /// These aren't actually declarators in the grammar, so we need to check that
 /// the user didn't specify any pieces that are not part of the deduction-guide
 /// grammar.
 void Sema::CheckDeductionGuideDeclarator(Declarator &D, QualType &R,
                                          StorageClass &SC) {
-  // FIXME: Implement
+  auto &DS = D.getMutableDeclSpec();
+  // We leave 'friend' and 'virtual' to be rejected in the normal way.
+  if (DS.hasTypeSpecifier() || DS.getTypeQualifiers() ||
+      DS.getStorageClassSpecLoc().isValid() || DS.isInlineSpecified() ||
+      DS.isNoreturnSpecified() || DS.isConstexprSpecified() ||
+      DS.isConceptSpecified()) {
+    BadSpecifierDiagnoser Diagnoser(
+        *this, D.getIdentifierLoc(),
+        diag::err_deduction_guide_invalid_specifier);
+
+    Diagnoser.check(DS.getStorageClassSpecLoc(), DS.getStorageClassSpec());
+    DS.ClearStorageClassSpecs();
+    SC = SC_None;
+
+    // 'explicit' is permitted.
+    Diagnoser.check(DS.getInlineSpecLoc(), "inline");
+    Diagnoser.check(DS.getNoreturnSpecLoc(), "_Noreturn");
+    Diagnoser.check(DS.getConstexprSpecLoc(), "constexpr");
+    Diagnoser.check(DS.getConceptSpecLoc(), "concept");
+    DS.ClearConstexprSpec();
+    DS.ClearConceptSpec();
+
+    Diagnoser.check(DS.getConstSpecLoc(), "const");
+    Diagnoser.check(DS.getRestrictSpecLoc(), "__restrict");
+    Diagnoser.check(DS.getVolatileSpecLoc(), "volatile");
+    Diagnoser.check(DS.getAtomicSpecLoc(), "_Atomic");
+    Diagnoser.check(DS.getUnalignedSpecLoc(), "__unaligned");
+    DS.ClearTypeQualifiers();
+
+    Diagnoser.check(DS.getTypeSpecComplexLoc(), DS.getTypeSpecComplex());
+    Diagnoser.check(DS.getTypeSpecSignLoc(), DS.getTypeSpecSign());
+    Diagnoser.check(DS.getTypeSpecWidthLoc(), DS.getTypeSpecWidth());
+    Diagnoser.check(DS.getTypeSpecTypeLoc(), DS.getTypeSpecType());
+    DS.ClearTypeSpecType();
+  }
+
+  if (D.isInvalidType())
+    return;
+
+  // Check the declarator is simple enough.
+  bool FoundFunction = false;
+  for (const DeclaratorChunk &Chunk : llvm::reverse(D.type_objects())) {
+    if (Chunk.Kind == DeclaratorChunk::Paren)
+      continue;
+    if (Chunk.Kind != DeclaratorChunk::Function || FoundFunction) {
+      Diag(D.getDeclSpec().getLocStart(),
+          diag::err_deduction_guide_with_complex_decl)
+        << D.getSourceRange();
+      break;
+    }
+    if (!Chunk.Fun.hasTrailingReturnType()) {
+      Diag(D.getName().getLocStart(),
+           diag::err_deduction_guide_no_trailing_return_type);
+      break;
+    }
+    FoundFunction = true;
+  }
+
+  // FIXME: Check that the return type can instantiate to a specialization of
+  // the template specified as the deduction-guide's name.
 }
 
 //===----------------------------------------------------------------------===//