[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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@359949 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 48 insertions, 0 deletions

diff --git a/unittests/AST/Language.cpp b/unittests/AST/Language.cpp
index 210014b3cd..68b78a3179 100644
--- a/unittests/AST/Language.cpp
+++ b/unittests/AST/Language.cpp
@@ -34,6 +34,9 @@ ArgVector getBasicRunOptionsForLanguage(Language Lang) {
   case Lang_CXX14:
     BasicArgs = {"-std=c++14", "-frtti"};
     break;
+  case Lang_CXX2a:
+    BasicArgs = {"-std=c++2a", "-frtti"};
+    break;
   case Lang_OpenCL:
   case Lang_OBJCXX:
     llvm_unreachable("Not implemented yet!");
diff --git a/unittests/AST/Language.h b/unittests/AST/Language.h
index cd19fb7b09..dd61ef8223 100644
--- a/unittests/AST/Language.h
+++ b/unittests/AST/Language.h
@@ -28,6 +28,7 @@ enum Language {
     Lang_CXX,
     Lang_CXX11,
     Lang_CXX14,
+    Lang_CXX2a,
     Lang_OpenCL,
     Lang_OBJCXX
 };
diff --git a/unittests/AST/MatchVerifier.h b/unittests/AST/MatchVerifier.h
index 1d1bf57db1..7aca7f498e 100644
--- a/unittests/AST/MatchVerifier.h
+++ b/unittests/AST/MatchVerifier.h
@@ -108,6 +108,10 @@ testing::AssertionResult MatchVerifier<NodeType>::match(
     Args.push_back("-std=c++14");
     FileName = "input.cc";
     break;
+  case Lang_CXX2a:
+    Args.push_back("-std=c++2a");
+    FileName = "input.cc";
+    break;
   case Lang_OpenCL:
     FileName = "input.cl";
     break;
diff --git a/unittests/AST/StructuralEquivalenceTest.cpp b/unittests/AST/StructuralEquivalenceTest.cpp
index 211b9539cf..5bb4f7e122 100644
--- a/unittests/AST/StructuralEquivalenceTest.cpp
+++ b/unittests/AST/StructuralEquivalenceTest.cpp
@@ -806,6 +806,26 @@ TEST_F(StructuralEquivalenceTest, CompareSameDeclWithMultiple) {
   EXPECT_FALSE(testStructuralMatch(t));
 }
 
+TEST_F(StructuralEquivalenceTest, ExplicitBoolDifferent) {
+  auto Decls = makeNamedDecls("struct foo {explicit(false) foo(int);};",
+                              "struct foo {explicit(true) foo(int);};", Lang_CXX2a);
+  CXXConstructorDecl *First = FirstDeclMatcher<CXXConstructorDecl>().match(
+      get<0>(Decls), cxxConstructorDecl(hasName("foo")));
+  CXXConstructorDecl *Second = FirstDeclMatcher<CXXConstructorDecl>().match(
+      get<1>(Decls), cxxConstructorDecl(hasName("foo")));
+  EXPECT_FALSE(testStructuralMatch(First, Second));
+}
+
+TEST_F(StructuralEquivalenceTest, ExplicitBoolSame) {
+  auto Decls = makeNamedDecls("struct foo {explicit(true) foo(int);};",
+                              "struct foo {explicit(true) foo(int);};", Lang_CXX2a);
+  CXXConstructorDecl *First = FirstDeclMatcher<CXXConstructorDecl>().match(
+      get<0>(Decls), cxxConstructorDecl(hasName("foo")));
+  CXXConstructorDecl *Second = FirstDeclMatcher<CXXConstructorDecl>().match(
+      get<1>(Decls), cxxConstructorDecl(hasName("foo")));
+  EXPECT_TRUE(testStructuralMatch(First, Second));
+}
+
 struct StructuralEquivalenceEnumTest : StructuralEquivalenceTest {};
 
 TEST_F(StructuralEquivalenceEnumTest, FwdDeclEnumShouldBeEqualWithFwdDeclEnum) {
@@ -853,5 +873,25 @@ TEST_F(StructuralEquivalenceTemplateTest, DifferentTemplateArgKind) {
   EXPECT_FALSE(testStructuralMatch(t));
 }
 
+TEST_F(StructuralEquivalenceTemplateTest, ExplicitBoolSame) {
+  auto Decls = makeNamedDecls("template <bool b> struct foo {explicit(b) foo(int);};",
+                              "template <bool b> struct foo {explicit(b) foo(int);};", Lang_CXX2a);
+  CXXConstructorDecl *First = FirstDeclMatcher<CXXConstructorDecl>().match(
+      get<0>(Decls), cxxConstructorDecl(hasName("foo<b>")));
+  CXXConstructorDecl *Second = FirstDeclMatcher<CXXConstructorDecl>().match(
+      get<1>(Decls), cxxConstructorDecl(hasName("foo<b>")));
+  EXPECT_TRUE(testStructuralMatch(First, Second));
+}
+
+TEST_F(StructuralEquivalenceTemplateTest, ExplicitBoolDifference) {
+  auto Decls = makeNamedDecls("template <bool b> struct foo {explicit(b) foo(int);};",
+                              "template <bool b> struct foo {explicit(!b) foo(int);};", Lang_CXX2a);
+  CXXConstructorDecl *First = FirstDeclMatcher<CXXConstructorDecl>().match(
+      get<0>(Decls), cxxConstructorDecl(hasName("foo<b>")));
+  CXXConstructorDecl *Second = FirstDeclMatcher<CXXConstructorDecl>().match(
+      get<1>(Decls), cxxConstructorDecl(hasName("foo<b>")));
+  EXPECT_FALSE(testStructuralMatch(First, Second));
+}
+
 } // end namespace ast_matchers
 } // end namespace clang