[ASTMatchers] HasNameMatcher handles extern "C"

Summary: Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=42193 | hasName AST matcher is confused by extern "C" in namespace. ]]

Reviewers: klimek, aaron.ballman, gribozavr2

Reviewed By: aaron.ballman

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75202

(cherry picked from commit 16cabf2)

Author: njames93

clang/lib/ASTMatchers/ASTMatchersInternal.cpp

@@ -523,7 +523,13 @@ bool HasNameMatcher::matchesNodeFullFast(const NamedDecl &Node) const {
   if (Ctx->isFunctionOrMethod())
     return Patterns.foundMatch(/*AllowFullyQualified=*/false);
 
-  for (; Ctx && isa<NamedDecl>(Ctx); Ctx = Ctx->getParent()) {
+  for (; Ctx; Ctx = Ctx->getParent()) {
+    // Linkage Spec can just be ignored
+    // FIXME: Any other DeclContext kinds that can be safely disregarded
+    if (isa<LinkageSpecDecl>(Ctx))
+      continue;
+    if (!isa<NamedDecl>(Ctx))
+      break;
     if (Patterns.foundMatch(/*AllowFullyQualified=*/false))
       return true;
 

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

@@ -1520,6 +1520,21 @@ TEST(Matcher, HasNameSupportsFunctionScope) {
   EXPECT_TRUE(matches(code, fieldDecl(hasName("::a::F(int)::S::m"))));
 }
 
+TEST(Matcher, HasNameQualifiedSupportsLinkage) {
+  // https://bugs.llvm.org/show_bug.cgi?id=42193
+  std::string code = R"cpp(namespace foo { extern "C" void test(); })cpp";
+  EXPECT_TRUE(matches(code, functionDecl(hasName("test"))));
+  EXPECT_TRUE(matches(code, functionDecl(hasName("foo::test"))));
+  EXPECT_TRUE(matches(code, functionDecl(hasName("::foo::test"))));
+  EXPECT_TRUE(notMatches(code, functionDecl(hasName("::test"))));
+
+  code = R"cpp(namespace foo { extern "C" { void test(); } })cpp";
+  EXPECT_TRUE(matches(code, functionDecl(hasName("test"))));
+  EXPECT_TRUE(matches(code, functionDecl(hasName("foo::test"))));
+  EXPECT_TRUE(matches(code, functionDecl(hasName("::foo::test"))));
+  EXPECT_TRUE(notMatches(code, functionDecl(hasName("::test"))));
+}
+
 TEST(Matcher, HasAnyName) {
   const std::string Code = "namespace a { namespace b { class C; } }";