[clang-rename] Handle designated initializers.

clang Tooling, and more specifically Refactoring/Rename, have support
code to extract source locations given a Unified Symbol Resolution set.
This support code is used by clang-rename and other tools that might not
be in the tree.

Currently field designated initializer are not supported.
So, renaming S::a to S::b in this code:

  S s = { .a = 10 };

will not extract the field designated initializer for a (the 'a' after the
dot).

This patch adds support for field designated initialized to
RecursiveSymbolVisitor and RenameLocFinder that is used in
createRenameAtomicChanges.

Differential Revision: https://reviews.llvm.org/D100310

clang/include/clang/Tooling/Refactoring/RecursiveSymbolVisitor.h

@@ -122,6 +122,17 @@ public:
     return BaseType::TraverseNestedNameSpecifierLoc(NNS);
   }
 
+  bool VisitDesignatedInitExpr(const DesignatedInitExpr *E) {
+    for (const DesignatedInitExpr::Designator &D : E->designators()) {
+      if (D.isFieldDesignator() && D.getField()) {
+        const FieldDecl *Decl = D.getField();
+        if (!visit(Decl, D.getFieldLoc(), D.getFieldLoc()))
+          return false;
+      }
+    }
+    return true;
+  }
+
 private:
   const SourceManager &SM;
   const LangOptions &LangOpts;

clang/lib/Tooling/Refactoring/Rename/USRLocFinder.cpp

@@ -226,6 +226,24 @@ public:
     return true;
   }
 
+  bool VisitDesignatedInitExpr(const DesignatedInitExpr *E) {
+    for (const DesignatedInitExpr::Designator &D : E->designators()) {
+      if (D.isFieldDesignator() && D.getField()) {
+        const FieldDecl *Decl = D.getField();
+        if (isInUSRSet(Decl)) {
+          auto StartLoc = D.getFieldLoc();
+          auto EndLoc = D.getFieldLoc();
+          RenameInfos.push_back({StartLoc, EndLoc,
+                                 /*FromDecl=*/nullptr,
+                                 /*Context=*/nullptr,
+                                 /*Specifier=*/nullptr,
+                                 /*IgnorePrefixQualifiers=*/true});
+        }
+      }
+    }
+    return true;
+  }
+
   bool VisitCXXConstructorDecl(const CXXConstructorDecl *CD) {
     // Fix the constructor initializer when renaming class members.
     for (const auto *Initializer : CD->inits()) {

clang/unittests/Rename/RenameClassTest.cpp

@@ -780,6 +780,27 @@ TEST_F(RenameClassTest, UsingAlias) {
   CompareSnippets(Expected, After);
 }
 
+TEST_F(ClangRenameTest, FieldDesignatedInitializers) {
+  std::string Before = R"(
+      struct S {
+        int a;
+      };
+      void foo() {
+        S s = { .a = 10 };
+        s.a = 20;
+      })";
+  std::string Expected = R"(
+      struct S {
+        int b;
+      };
+      void foo() {
+        S s = { .b = 10 };
+        s.b = 20;
+      })";
+  std::string After = runClangRenameOnCode(Before, "S::a", "S::b");
+  CompareSnippets(Expected, After);
+}
+
 // FIXME: investigate why the test fails when adding a new USR to the USRSet.
 TEST_F(ClangRenameTest, DISABLED_NestedTemplates) {
   std::string Before = R"(