From 824913bdb71024a9d90942c0249e674c01001214 Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall@gmail.com>
Date: Fri, 9 Mar 2018 13:25:29 +0000
Subject: [PATCH] [clangd] Don't index template specializations.

Summary:
These have different USRs than the underlying entity, but are not typically
interesting in their own right and can be numerous (e.g. generated traits).

Reviewers: ioeric

Subscribers: klimek, ilya-biryukov, jkorous-apple, cfe-commits

Differential Revision: https://reviews.llvm.org/D44298

llvm-svn: 327127
---
 clang-tools-extra/clangd/index/SymbolCollector.cpp  |  8 +++++++-
 .../unittests/clangd/SymbolCollectorTests.cpp       | 13 +++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/clangd/index/SymbolCollector.cpp b/clang-tools-extra/clangd/index/SymbolCollector.cpp
index fe994d0137ec..93bd3f75a9ce 100644
--- a/clang-tools-extra/clangd/index/SymbolCollector.cpp
+++ b/clang-tools-extra/clangd/index/SymbolCollector.cpp
@@ -115,10 +115,16 @@ bool shouldFilterDecl(const NamedDecl *ND, ASTContext *ASTCtx,
   //   * enum constants in unscoped enum decl (e.g. "red" in "enum {red};")
   auto InTopLevelScope = hasDeclContext(
       anyOf(namespaceDecl(), translationUnitDecl(), linkageSpecDecl()));
+  // Don't index template specializations.
+  auto IsSpecialization =
+      anyOf(functionDecl(isExplicitTemplateSpecialization()),
+            cxxRecordDecl(isExplicitTemplateSpecialization()),
+            varDecl(isExplicitTemplateSpecialization()));
   if (match(decl(allOf(unless(isExpansionInMainFile()),
                        anyOf(InTopLevelScope,
                              hasDeclContext(enumDecl(InTopLevelScope,
-                                                     unless(isScoped())))))),
+                                                     unless(isScoped())))),
+                       unless(IsSpecialization))),
             *ND, *ASTCtx)
           .empty())
     return true;
diff --git a/clang-tools-extra/unittests/clangd/SymbolCollectorTests.cpp b/clang-tools-extra/unittests/clangd/SymbolCollectorTests.cpp
index 363fd002e563..c6a155a4a369 100644
--- a/clang-tools-extra/unittests/clangd/SymbolCollectorTests.cpp
+++ b/clang-tools-extra/unittests/clangd/SymbolCollectorTests.cpp
@@ -198,6 +198,19 @@ TEST_F(SymbolCollectorTest, CollectSymbols) {
                    QName("foo::bar::v2"), QName("foo::baz")}));
 }
 
+TEST_F(SymbolCollectorTest, Template) {
+  Annotations Header(R"(
+    // Template is indexed, specialization and instantiation is not.
+    template <class T> struct [[Tmpl]] {T x = 0};
+    template <> struct Tmpl<int> {};
+    extern template struct Tmpl<float>;
+    template struct Tmpl<double>;
+  )");
+  runSymbolCollector(Header.code(), /*Main=*/"");
+  EXPECT_THAT(Symbols, UnorderedElementsAreArray({AllOf(
+                           QName("Tmpl"), DeclRange(Header.offsetRange()))}));
+}
+
 TEST_F(SymbolCollectorTest, Locations) {
   Annotations Header(R"cpp(
     // Declared in header, defined in main.