Fix test for the hasExternalFormalLinkage matcher

[gribozavr]

Summary

Names of local variables have no linkage (see C++20 [basic.link] p8).

Names of variables in unnamed namespace have internal linkage (see C++20
[basic.link] p4).

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

struct MyTemplate {
       MyTemplate() : field_(__null) {}
       T* field_;
     };
   )";
   EXPECT_TRUE(matches(kTest, expr(nullPointerConstant())));
 }
 
 TEST(HasExternalFormalLinkage, Basic) {
-  EXPECT_TRUE(matches("int a = 0;", namedDecl(hasExternalFormalLinkage())));
-  EXPECT_TRUE(
-      notMatches("static int a = 0;", namedDecl(hasExternalFormalLinkage())));
+  EXPECT_TRUE(matches("int a = 0;",
+                      namedDecl(hasName("a"), hasExternalFormalLinkage())));
+  EXPECT_TRUE(notMatches("static int a = 0;",
+                         namedDecl(hasName("a"), hasExternalFormalLinkage())));
   EXPECT_TRUE(notMatches("static void f(void) { int a = 0; }",
-                         namedDecl(hasExternalFormalLinkage())));
-  EXPECT_TRUE(matches("void f(void) { int a = 0; }",
-                      namedDecl(hasExternalFormalLinkage())));
-
-  // Despite having internal semantic linkage, the anonymous namespace member
-  // has external linkage because the member has a unique name in all
-  // translation units.
-  EXPECT_TRUE(matches("namespace { int a = 0; }",
-                      namedDecl(hasExternalFormalLinkage())));
+                         namedDecl(hasName("a"), hasExternalFormalLinkage())));
+  EXPECT_TRUE(notMatches("void f(void) { int a = 0; }",
+                         namedDecl(hasName("a"), hasExternalFormalLinkage())));
+  EXPECT_TRUE(notMatches("namespace { int a = 0; }",
+                         namedDecl(hasName("a"), hasExternalFormalLinkage())));
 }
 
 TEST(HasDefaultArgument, Basic) {
   EXPECT_TRUE(
       matches("void x(int val = 0) {}", parmVarDecl(hasDefaultArgument())));
   EXPECT_TRUE(
       notMatches("void x(int val) {}", parmVarDecl(hasDefaultArgument())));
 }