[clangd] Refine the way of checking a declaration is referenced by the written code.

Summary:
The previous solution (checking the AST) is not a reliable way to
determine whether a declaration is explicitly referenced by the source
code, we are still missing a few cases.

Reviewers: ilya-biryukov

Subscribers: ioeric, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D55191

llvm-svn: 349033

clang-tools-extra/clangd/XRefs.cpp

@@ -139,21 +139,19 @@ public:
                       SourceLocation Loc,
                       index::IndexDataConsumer::ASTNodeInfo ASTNode) override {
     if (Loc == SearchedLocation) {
-      // Check whether the E has an implicit AST node (e.g. ImplicitCastExpr).
-      auto hasImplicitExpr = [](const Expr *E) {
-        if (!E || E->child_begin() == E->child_end())
+      auto isImplicitExpr = [](const Expr *E) {
+        if (!E)
           return false;
-        // Use the first child is good enough for most cases -- normally the
-        // expression returned by handleDeclOccurence contains exactly one
-        // child expression.
-        const auto *FirstChild = *E->child_begin();
-        return isa<ExprWithCleanups>(FirstChild) ||
-               isa<MaterializeTemporaryExpr>(FirstChild) ||
-               isa<CXXBindTemporaryExpr>(FirstChild) ||
-               isa<ImplicitCastExpr>(FirstChild);
+        // We assume that a constructor expression is implict (was inserted by
+        // clang) if it has an invalid paren/brace location, since such
+        // experssion is impossible to write down.
+        if (const auto *CtorExpr = dyn_cast<CXXConstructExpr>(E))
+          return CtorExpr->getNumArgs() > 0 &&
+                 CtorExpr->getParenOrBraceRange().isInvalid();
+        return isa<ImplicitCastExpr>(E);
       };
 
-      bool IsExplicit = !hasImplicitExpr(ASTNode.OrigE);
+      bool IsExplicit = !isImplicitExpr(ASTNode.OrigE);
       // Find and add definition declarations (for GoToDefinition).
       // We don't use parameter `D`, as Parameter `D` is the canonical
       // declaration, which is the first declaration of a redeclarable

clang-tools-extra/unittests/clangd/XRefsTests.cpp

@@ -1225,6 +1225,53 @@ TEST(FindReferences, WithinAST) {
   }
 }
 
+TEST(FindReferences, ExplicitSymbols) {
+  const char *Tests[] = {
+      R"cpp(
+      struct Foo { Foo* [self]() const; };
+      void f() {
+        if (Foo* T = foo.[^self]()) {} // Foo member call expr.
+      }
+      )cpp",
+
+      R"cpp(
+      struct Foo { Foo(int); };
+      Foo f() {
+        int [b];
+        return [^b]; // Foo constructor expr.
+      }
+      )cpp",
+
+      R"cpp(
+      struct Foo {};
+      void g(Foo);
+      Foo [f]();
+      void call() {
+        g([^f]());  // Foo constructor expr.
+      }
+      )cpp",
+
+      R"cpp(
+      void [foo](int);
+      void [foo](double);
+
+      namespace ns {
+      using ::[fo^o];
+      }
+      )cpp",
+  };
+  for (const char *Test : Tests) {
+    Annotations T(Test);
+    auto AST = TestTU::withCode(T.code()).build();
+    std::vector<Matcher<Location>> ExpectedLocations;
+    for (const auto &R : T.ranges())
+      ExpectedLocations.push_back(RangeIs(R));
+    EXPECT_THAT(findReferences(AST, T.point()),
+                ElementsAreArray(ExpectedLocations))
+        << Test;
+  }
+}
+
 TEST(FindReferences, NeedsIndex) {
   const char *Header = "int foo();";
   Annotations Main("int main() { [[f^oo]](); }");