[clang][ASTImporter] Add import of 'BitIntType'

[strimo378]

I think the ASTImporter class has in general a completion problem. What do you think about rewriting it that any missing Visit* function for Type, Decl and Stmt produces an compiler error?

clang/include/clang/ASTMatchers/ASTMatchers.h

 /// \endcode
 /// atomicType(hasValueType(isInteger()))
 ///  matches "_Atomic(int) i"
 ///
 /// Usable as: Matcher<AtomicType>
 AST_TYPELOC_TRAVERSE_MATCHER_DECL(hasValueType, getValue,
                                   AST_POLYMORPHIC_SUPPORTED_TYPES(AtomicType));
 
+/// Matches bitint types.
+///
+/// Given
+/// \code
+///   _BitInt(10) i;
+/// \endcode
+/// bitIntType()
+///   matches "_BitInt(10) i"
+extern const AstTypeMatcher<BitIntType> bitIntType;
+
 /// Matches types nodes representing C++11 auto types.
 ///
 /// Given:
 /// \code
 ///   auto n = 4;
 ///   int v[] = { 2, 3 }
 ///   for (auto i : v) { }
 /// \endcode

clang/lib/AST/ASTImporter.cpp

public:
     ExpectedType VisitElaboratedType(const ElaboratedType *T);
     ExpectedType VisitDependentNameType(const DependentNameType *T);
     ExpectedType VisitPackExpansionType(const PackExpansionType *T);
     ExpectedType VisitDependentTemplateSpecializationType(
         const DependentTemplateSpecializationType *T);
     ExpectedType VisitObjCInterfaceType(const ObjCInterfaceType *T);
     ExpectedType VisitObjCObjectType(const ObjCObjectType *T);
     ExpectedType VisitObjCObjectPointerType(const ObjCObjectPointerType *T);
+    ExpectedType VisitBitIntType(const BitIntType *T);
 
     // Importing declarations
     Error ImportDeclParts(NamedDecl *D, DeclarationName &Name, NamedDecl *&ToD,
                           SourceLocation &Loc);
     Error ImportDeclParts(
         NamedDecl *D, DeclContext *&DC, DeclContext *&LexicalDC,
         DeclarationName &Name, NamedDecl *&ToD, SourceLocation &Loc);
     Error ImportDefinitionIfNeeded(Decl *FromD, Decl *ToD = nullptr);

 ASTNodeImporter::VisitObjCObjectPointerType(const ObjCObjectPointerType *T) {
   ExpectedType ToPointeeTypeOrErr = import(T->getPointeeType());
   if (!ToPointeeTypeOrErr)
     return ToPointeeTypeOrErr.takeError();
 
   return Importer.getToContext().getObjCObjectPointerType(*ToPointeeTypeOrErr);
 }
 
+ExpectedType clang::ASTNodeImporter::VisitBitIntType(const BitIntType *T) {
+  return Importer.getToContext().getBitIntType(T->isUnsigned(),
+                                               T->getNumBits());
+}
+
 //----------------------------------------------------------------------------
 // Import Declarations
 //----------------------------------------------------------------------------
 Error ASTNodeImporter::ImportDeclParts(
     NamedDecl *D, DeclContext *&DC, DeclContext *&LexicalDC,
     DeclarationName &Name, NamedDecl *&ToD, SourceLocation &Loc) {
   // Check if RecordDecl is in FunctionDecl parameters to avoid infinite loop.
   // example: int struct_in_proto(struct data_t{int a;int b;} *d);

clang/unittests/AST/ASTImporterTest.cpp

 TEST_P(ImportType, ImportAtomicType) {
   MatchVerifier<Decl> Verifier;
   testImport(
       "void declToImport() { typedef _Atomic(int) a_int; }",
       Lang_CXX11, "", Lang_CXX11, Verifier,
       functionDecl(hasDescendant(typedefDecl(has(atomicType())))));
 }
 
+TEST_P(ImportType, ImportBitIntType) {
+  MatchVerifier<Decl> Verifier;
+  testImport("void declToImport() { typedef _BitInt(10) bit_int; }", Lang_CXX11,
+             "", Lang_CXX11, Verifier,
+             functionDecl(hasDescendant(typedefDecl(has(bitIntType())))));
+}
+
 TEST_P(ImportType, ImportUsingType) {
   MatchVerifier<Decl> Verifier;
   testImport("struct C {};"
              "void declToImport() { using ::C; new C{}; }",
              Lang_CXX11, "", Lang_CXX11, Verifier,
              functionDecl(hasDescendant(cxxNewExpr(hasType(pointerType(
                  pointee(elaboratedType(namesType(usingType())))))))));
 }