[ASTMatchers] Add narrowing matcher: hasExternalFormalLinkage

[thegameg]

Summary

Matches NamedDecl nodes whose linkage is external.

[aaron.ballman]

A few minor nits, but thank you for the patch!

include/clang/ASTMatchers/ASTMatchers.h

5481

It might also be good to point out the case of an anonymous namespace member which has external linkage (despite having internal semantic linkage because the member has a unique name in all translation units).

unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

1942

Should use EXPECT_TRUE with notMatches() here and below.

[thegameg]

Mention UniqueExternalLinkage type, add a test according to it.
EXPECT_FALSE(matches( -> EXPECT_TRUE(notMatches(

[thegameg]

Sorry, sent the wrong patch.

[alexfh]

docs/LibASTMatchersReference.html

2774

Please regenerate the .html file.

[thegameg]

LibASTMatchersReference.html regenerated using dump_ast_matchers.py.

[aaron.ballman]

include/clang/ASTMatchers/ASTMatchers.h

5490–5497

I wouldn't copy and paste the text from Linkage.h, merely point out below: Example matches f() because it has external formal linkage despite being unique to the translation unit as though it has internal linkage (matcher = ...).

[thegameg]

Update documentation according to @aaron.ballman's remarks.

[aaron.ballman]

LGTM, thank you!

[thegameg]

Thank you for the review.

I don't have commit access, would you commit this for me, please?

Thanks!

[aaron.ballman]

I've commit in r278926. (I can't close because @alexfh hasn't accepted yet; Alex, can you accept & close?)

[alexfh]

LG

[alexfh]

In D23585#517942, @aaron.ballman wrote:

I've commit in r278926. (I can't close because @alexfh hasn't accepted yet; Alex, can you accept & close?)

Sure. Done.

BTW, Phabricator can close revisions automatically on commit: http://llvm.org/docs/Phabricator.html#committing-a-change

docs/LibASTMatchersReference.html

 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1NamedDecl.html">NamedDecl</a>&gt;</td><td class="name" onclick="toggle('hasExternalFormalLinkage0')"><a name="hasExternalFormalLinkage0Anchor">hasExternalFormalLinkage</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="hasExternalFormalLinkage0"><pre>Matches NamedDecl nodes whose linkage is external.
+
+Example matches foo
+  void foo(void) { }
+
+Example matches i
+  int i = 0;
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="http://clang.llvm.org/doxygen/classclang_1_1NamespaceDecl.html">NamespaceDecl</a>&gt;</td><td class="name" onclick="toggle('isAnonymous0')"><a name="isAnonymous0Anchor">isAnonymous</a></td><td></td></tr>
 <tr><td colspan="4" class="doc" id="isAnonymous0"><pre>Matches anonymous namespace declarations.
 

include/clang/ASTMatchers/ASTMatchers.h

   return false;
 }
 
+/// \brief Matches a declaration that has external formal linkage.
+///
+/// Example matches only z (matcher = varDecl(hasExternalFormalLinkage()))
+/// \code
+/// void f() {
+///   int x;
+///   static int y;
+/// }
+/// int z;
+/// \endcode
+///
+/// From clang/Basic/Linkage.h:
+/// > UniqueExternalLinkage:
+/// > External linkage within a unique namespace.
+/// > From the language perspective, these entities have external
+/// > linkage. However, since they reside in an anonymous namespace,
+/// > their names are unique to this translation unit, which is
+/// > equivalent to having internal linkage from the code-generation
+/// > point of view.
+///
+/// Example matches f (matcher = functionDecl(hasExternalFormalLinkage()))
+/// \code
+/// namespace {
+/// void f() {}
+/// }
+/// \endcode
+AST_MATCHER(NamedDecl, hasExternalFormalLinkage) {
+  return Node.hasExternalFormalLinkage();
+}
+
 } // end namespace ast_matchers
 } // end namespace clang
 

lib/ASTMatchers/Dynamic/Registry.cpp

   REGISTER_MATCHER(hasEitherOperand);
   REGISTER_MATCHER(hasElementType);
   REGISTER_MATCHER(hasElse);
+  REGISTER_MATCHER(hasExternalFormalLinkage);
   REGISTER_MATCHER(hasFalseExpression);
   REGISTER_MATCHER(hasGlobalStorage);
   REGISTER_MATCHER(hasImplicitDestinationType);

unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

   EXPECT_TRUE(notMatches("int i = 0;", expr(nullPointerConstant())));
 }
 
+TEST(HasExternalFormalLinkage, Basic) {
+  EXPECT_TRUE(matches("int a = 0;", namedDecl(hasExternalFormalLinkage())));
+  EXPECT_TRUE(
+      notMatches("static int a = 0;", namedDecl(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())));
+}
+
 } // namespace ast_matchers
 } // namespace clang