[clang-tools-extra] e81c981 - [clangd] Don't collect templated decls for builtin templates (#78466)

[via cfe-commits]

Author: Younan Zhang
Date: 2024-01-19T10:54:47+08:00
New Revision: e81c981fe35483a4b7474e110ff1b5d02bc2cb00

URL: https://github.com/llvm/llvm-project/commit/e81c981fe35483a4b7474e110ff1b5d02bc2cb00
DIFF: https://github.com/llvm/llvm-project/commit/e81c981fe35483a4b7474e110ff1b5d02bc2cb00.diff

LOG: [clangd] Don't collect templated decls for builtin templates (#78466)

Builtin templates e.g. `__make_integer_seq`, `__type_pack_element` are
such that they don't have alias *Decls*.
[D133262](https://reviews.llvm.org/D133262) marked these as alias
templates, resulting in an attempt to collect their null "using" Decls
within our `TargetFinder`.

This fixes https://github.com/clangd/clangd/issues/1906.

Added: 
    

Modified: 
    clang-tools-extra/clangd/FindTarget.cpp
    clang-tools-extra/clangd/unittests/FindTargetTests.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clangd/FindTarget.cpp b/clang-tools-extra/clangd/FindTarget.cpp
index 839cf6332fe8b0..3d73e77b16aff4 100644
--- a/clang-tools-extra/clangd/FindTarget.cpp
+++ b/clang-tools-extra/clangd/FindTarget.cpp
@@ -443,9 +443,16 @@ struct TargetFinder {
           Outer.add(TST->getAliasedType(), Flags | Rel::Underlying);
           // Don't *traverse* the alias, which would result in traversing the
           // template of the underlying type.
-          Outer.report(
-              TST->getTemplateName().getAsTemplateDecl()->getTemplatedDecl(),
-              Flags | Rel::Alias | Rel::TemplatePattern);
+
+          TemplateDecl *TD = TST->getTemplateName().getAsTemplateDecl();
+          // Builtin templates e.g. __make_integer_seq, __type_pack_element
+          // are such that they don't have alias *decls*. Even then, we still
+          // traverse their desugared *types* so that instantiated decls are
+          // collected.
+          if (llvm::isa<BuiltinTemplateDecl>(TD))
+            return;
+          Outer.report(TD->getTemplatedDecl(),
+                       Flags | Rel::Alias | Rel::TemplatePattern);
         }
         // specializations of template template parameters aren't instantiated
         // into decls, so they must refer to the parameter itself.

diff  --git a/clang-tools-extra/clangd/unittests/FindTargetTests.cpp b/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
index fbd10c4a47a793..29cff68cf03b2e 100644
--- a/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
+++ b/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
@@ -709,6 +709,33 @@ TEST_F(TargetDeclTest, TypeAliasTemplate) {
                 Rel::Alias | Rel::TemplatePattern});
 }
 
+TEST_F(TargetDeclTest, BuiltinTemplates) {
+  Code = R"cpp(
+    template <class T, T... Index> struct integer_sequence {};
+    [[__make_integer_seq]]<integer_sequence, int, 3> X;
+  )cpp";
+  EXPECT_DECLS(
+      "TemplateSpecializationTypeLoc",
+      {"struct integer_sequence", Rel::TemplatePattern | Rel::Underlying},
+      {"template<> struct integer_sequence<int, <0, 1, 2>>",
+       Rel::TemplateInstantiation | Rel::Underlying});
+
+  // Dependent context.
+  Code = R"cpp(
+    template <class T, T... Index> struct integer_sequence;
+
+    template <class T, int N>
+    using make_integer_sequence = [[__make_integer_seq]]<integer_sequence, T, N>;
+  )cpp";
+  EXPECT_DECLS("TemplateSpecializationTypeLoc");
+
+  Code = R"cpp(
+    template <int N, class... Pack>
+    using type_pack_element = [[__type_pack_element]]<N, Pack...>;
+  )cpp";
+  EXPECT_DECLS("TemplateSpecializationTypeLoc");
+}
+
 TEST_F(TargetDeclTest, MemberOfTemplate) {
   Code = R"cpp(
     template <typename T> struct Foo {