[clang] adding explicit(bool) from c++2a

this patch adds support for the explicit bool specifier.

Changes:
- The parsing for the explicit(bool) specifier was added in ParseDecl.cpp.
- The storage of the explicit specifier was changed. the explicit specifier was stored as a boolean value in the FunctionDeclBitfields and in the DeclSpec class. now it is stored as a PointerIntPair<Expr*, 2> with a flag and a potential expression in CXXConstructorDecl, CXXDeductionGuideDecl, CXXConversionDecl and in the DeclSpec class.
- Following the AST change, Serialization, ASTMatchers, ASTComparator and ASTPrinter were adapted.
- Template instantiation was adapted to instantiate the potential expressions of the explicit(bool) specifier When instantiating their associated declaration.
- The Add*Candidate functions were adapted, they now take a Boolean indicating if the context allowing explicit constructor or conversion function and this boolean is used to remove invalid overloads that required template instantiation to be detected.
- Test for Semantic and Serialization were added.

This patch is not yet complete. I still need to check that interaction with CTAD and deduction guides is correct. and add more tests for AST operations. But I wanted first feedback.
Perhaps this patch should be spited in smaller patches, but making each patch testable as a standalone may be tricky.

Patch by Tyker

Differential Revision: https://reviews.llvm.org/D60934

llvm-svn: 359949

1 files changed, 41 insertions, 18 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index b90ab0457b2..b8740960fc5 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -657,14 +657,13 @@ bool Sema::MergeCXXFunctionDecl(FunctionDecl *New, FunctionDecl *Old,
     Invalid = true;
   }
 
-  // FIXME: It's not clear what should happen if multiple declarations of a
-  // deduction guide have different explicitness. For now at least we simply
-  // reject any case where the explicitness changes.
-  auto *NewGuide = dyn_cast<CXXDeductionGuideDecl>(New);
-  if (NewGuide && NewGuide->isExplicitSpecified() !=
-                      cast<CXXDeductionGuideDecl>(Old)->isExplicitSpecified()) {
-    Diag(New->getLocation(), diag::err_deduction_guide_explicit_mismatch)
-      << NewGuide->isExplicitSpecified();
+  // C++17 [temp.deduct.guide]p3:
+  //   Two deduction guide declarations in the same translation unit
+  //   for the same class template shall not have equivalent
+  //   parameter-declaration-clauses.
+  if (isa<CXXDeductionGuideDecl>(New) &&
+      !New->isFunctionTemplateSpecialization()) {
+    Diag(New->getLocation(), diag::err_deduction_guide_redeclared);
     Diag(Old->getLocation(), diag::note_previous_declaration);
   }
 
@@ -8638,12 +8637,12 @@ void Sema::CheckConversionDeclarator(Declarator &D, QualType &R,
     R = Context.getFunctionType(ConvType, None, Proto->getExtProtoInfo());
 
   // C++0x explicit conversion operators.
-  if (DS.isExplicitSpecified())
+  if (DS.hasExplicitSpecifier() && !getLangOpts().CPlusPlus2a)
     Diag(DS.getExplicitSpecLoc(),
          getLangOpts().CPlusPlus11
              ? diag::warn_cxx98_compat_explicit_conversion_functions
              : diag::ext_explicit_conversion_functions)
-        << SourceRange(DS.getExplicitSpecLoc());
+        << SourceRange(DS.getExplicitSpecRange());
 }
 
 /// ActOnConversionDeclarator - Called by ActOnDeclarator to complete
@@ -10866,6 +10865,28 @@ struct ComputingExceptionSpec {
 };
 }
 
+bool Sema::tryResolveExplicitSpecifier(ExplicitSpecifier &ExplicitSpec) {
+  llvm::APSInt Result;
+  ExprResult Converted = CheckConvertedConstantExpression(
+      ExplicitSpec.getExpr(), Context.BoolTy, Result, CCEK_ExplicitBool);
+  ExplicitSpec.setExpr(Converted.get());
+  if (Converted.isUsable() && !Converted.get()->isValueDependent()) {
+    ExplicitSpec.setKind(Result.getBoolValue()
+                             ? ExplicitSpecKind::ResolvedTrue
+                             : ExplicitSpecKind::ResolvedFalse);
+    return true;
+  }
+  ExplicitSpec.setKind(ExplicitSpecKind::Unresolved);
+  return false;
+}
+
+ExplicitSpecifier Sema::ActOnExplicitBoolSpecifier(Expr *ExplicitExpr) {
+  ExplicitSpecifier ES(ExplicitExpr, ExplicitSpecKind::Unresolved);
+  if (!ExplicitExpr->isTypeDependent())
+    tryResolveExplicitSpecifier(ES);
+  return ES;
+}
+
 static Sema::ImplicitExceptionSpecification
 ComputeDefaultedSpecialMemberExceptionSpec(
     Sema &S, SourceLocation Loc, CXXMethodDecl *MD, Sema::CXXSpecialMember CSM,
@@ -11014,9 +11035,9 @@ CXXConstructorDecl *Sema::DeclareImplicitDefaultConstructor(
     = Context.DeclarationNames.getCXXConstructorName(ClassType);
   DeclarationNameInfo NameInfo(Name, ClassLoc);
   CXXConstructorDecl *DefaultCon = CXXConstructorDecl::Create(
-      Context, ClassDecl, ClassLoc, NameInfo, /*Type*/QualType(),
-      /*TInfo=*/nullptr, /*isExplicit=*/false, /*isInline=*/true,
-      /*isImplicitlyDeclared=*/true, Constexpr);
+      Context, ClassDecl, ClassLoc, NameInfo, /*Type*/ QualType(),
+      /*TInfo=*/nullptr, ExplicitSpecifier(),
+      /*isInline=*/true, /*isImplicitlyDeclared=*/true, Constexpr);
   DefaultCon->setAccess(AS_public);
   DefaultCon->setDefaulted();
 
@@ -11135,7 +11156,7 @@ Sema::findInheritingConstructor(SourceLocation Loc,
 
   CXXConstructorDecl *DerivedCtor = CXXConstructorDecl::Create(
       Context, Derived, UsingLoc, NameInfo, TInfo->getType(), TInfo,
-      BaseCtor->isExplicit(), /*Inline=*/true,
+      BaseCtor->getExplicitSpecifier(), /*Inline=*/true,
       /*ImplicitlyDeclared=*/true, Constexpr,
       InheritedConstructor(Shadow, BaseCtor));
   if (Shadow->isInvalidDecl())
@@ -12588,8 +12609,9 @@ CXXConstructorDecl *Sema::DeclareImplicitCopyConstructor(
   //   member of its class.
   CXXConstructorDecl *CopyConstructor = CXXConstructorDecl::Create(
       Context, ClassDecl, ClassLoc, NameInfo, QualType(), /*TInfo=*/nullptr,
-      /*isExplicit=*/false, /*isInline=*/true, /*isImplicitlyDeclared=*/true,
-      Constexpr);
+      ExplicitSpecifier(),
+      /*isInline=*/true,
+      /*isImplicitlyDeclared=*/true, Constexpr);
   CopyConstructor->setAccess(AS_public);
   CopyConstructor->setDefaulted();
 
@@ -12718,8 +12740,9 @@ CXXConstructorDecl *Sema::DeclareImplicitMoveConstructor(
   //   member of its class.
   CXXConstructorDecl *MoveConstructor = CXXConstructorDecl::Create(
       Context, ClassDecl, ClassLoc, NameInfo, QualType(), /*TInfo=*/nullptr,
-      /*isExplicit=*/false, /*isInline=*/true, /*isImplicitlyDeclared=*/true,
-      Constexpr);
+      ExplicitSpecifier(),
+      /*isInline=*/true,
+      /*isImplicitlyDeclared=*/true, Constexpr);
   MoveConstructor->setAccess(AS_public);
   MoveConstructor->setDefaulted();