From 100dbd15624c1ac8d1210e7748462e20fed9a9d9 Mon Sep 17 00:00:00 2001
From: Nathan Ridge <zeratul976@hotmail.com>
Date: Sun, 19 Jul 2020 02:26:49 -0400
Subject: [PATCH] [clangd] Handle deduction guides in TargetFinder and
 ExplicitReferenceCollector

Summary: Fixes https://github.com/clangd/clangd/issues/463.

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D84122
---
 clang-tools-extra/clangd/FindTarget.cpp            | 11 ++++
 .../clangd/unittests/FindTargetTests.cpp           | 62 +++++++++++++++++-----
 2 files changed, 59 insertions(+), 14 deletions(-)

diff --git a/clang-tools-extra/clangd/FindTarget.cpp b/clang-tools-extra/clangd/FindTarget.cpp
index 627f40c8543..c2887f3306f 100644
--- a/clang-tools-extra/clangd/FindTarget.cpp
+++ b/clang-tools-extra/clangd/FindTarget.cpp
@@ -302,6 +302,8 @@ public:
       // Record the underlying decl instead, if allowed.
       D = USD->getTargetDecl();
       Flags |= Rel::Underlying; // continue with the underlying decl.
+    } else if (const auto *DG = dyn_cast<CXXDeductionGuideDecl>(D)) {
+      D = DG->getDeducedTemplate();
     }
 
     if (const Decl *Pat = getTemplatePattern(D)) {
@@ -659,6 +661,15 @@ llvm::SmallVector<ReferenceLoc, 2> refInDecl(const Decl *D) {
                                   /*IsDecl=*/true,
                                   {ND}});
     }
+
+    void VisitCXXDeductionGuideDecl(const CXXDeductionGuideDecl *DG) {
+      // The class template name in a deduction guide targets the class
+      // template.
+      Refs.push_back(ReferenceLoc{DG->getQualifierLoc(),
+                                  DG->getNameInfo().getLoc(),
+                                  /*IsDecl=*/false,
+                                  {DG->getDeducedTemplate()}});
+    }
   };
 
   Visitor V;
diff --git a/clang-tools-extra/clangd/unittests/FindTargetTests.cpp b/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
index bf5cc62411b..fa8f4935b1d 100644
--- a/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
+++ b/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
@@ -376,6 +376,8 @@ TEST_F(TargetDeclTest, ClassTemplate) {
                {"template<> class Foo<int *>", Rel::TemplateInstantiation},
                {"template <typename T> class Foo<T *>", Rel::TemplatePattern});
 
+  Flags.push_back("-std=c++17"); // for CTAD tests
+
   Code = R"cpp(
     // Class template argument deduction
     template <typename T>
@@ -386,9 +388,20 @@ TEST_F(TargetDeclTest, ClassTemplate) {
       [[Test]] a(5);
     }
   )cpp";
-  Flags.push_back("-std=c++17");
   EXPECT_DECLS("DeducedTemplateSpecializationTypeLoc",
                {"struct Test", Rel::TemplatePattern});
+
+  Code = R"cpp(
+    // Deduction guide
+    template <typename T>
+    struct Test {
+      template <typename I>
+      Test(I, I);
+    };
+    template <typename I>
+    [[Test]](I, I) -> Test<typename I::type>;
+  )cpp";
+  EXPECT_DECLS("CXXDeductionGuideDecl", {"template <typename T> struct Test"});
 }
 
 TEST_F(TargetDeclTest, Concept) {
@@ -792,8 +805,8 @@ TEST_F(FindExplicitReferencesTest, All) {
            goto $1^ten;
          }
        )cpp",
-       "0: targets = {ten}, decl\n"
-       "1: targets = {ten}\n"},
+        "0: targets = {ten}, decl\n"
+        "1: targets = {ten}\n"},
        // Simple templates.
        {R"cpp(
           template <class T> struct vector { using value_type = T; };
@@ -1295,7 +1308,7 @@ TEST_F(FindExplicitReferencesTest, All) {
         "6: targets = {bar}, decl\n"
         "7: targets = {foo()::Bar::Foo}\n"
         "8: targets = {foo()::Baz::Field}\n"},
-      {R"cpp(
+       {R"cpp(
            template<typename T>
            void crash(T);
            template<typename T>
@@ -1305,10 +1318,9 @@ TEST_F(FindExplicitReferencesTest, All) {
         )cpp",
         "0: targets = {crash}\n"
         "1: targets = {}\n"
-        "2: targets = {T}\n"
-      },
-      // unknown template name should not crash.
-      {R"cpp(
+        "2: targets = {T}\n"},
+       // unknown template name should not crash.
+       {R"cpp(
         template <template <typename> typename T>
         struct Base {};
         namespace foo {
@@ -1316,12 +1328,34 @@ TEST_F(FindExplicitReferencesTest, All) {
         struct $1^Derive : $2^Base<$3^T::template $4^Unknown> {};
         }
       )cpp",
-      "0: targets = {foo::Derive::T}, decl\n"
-      "1: targets = {foo::Derive}, decl\n"
-      "2: targets = {Base}\n"
-      "3: targets = {foo::Derive::T}\n"
-      "4: targets = {}, qualifier = 'T::'\n"},
-    };
+        "0: targets = {foo::Derive::T}, decl\n"
+        "1: targets = {foo::Derive}, decl\n"
+        "2: targets = {Base}\n"
+        "3: targets = {foo::Derive::T}\n"
+        "4: targets = {}, qualifier = 'T::'\n"},
+       // deduction guide
+       {R"cpp(
+          namespace foo {
+            template <typename $0^T>
+            struct $1^Test {
+              template <typename $2^I>
+              $3^Test($4^I);
+            };
+            template <typename $5^I>
+            $6^Test($7^I) -> $8^Test<typename $9^I::$10^type>;
+          }
+        )cpp",
+        "0: targets = {T}, decl\n"
+        "1: targets = {foo::Test}, decl\n"
+        "2: targets = {I}, decl\n"
+        "3: targets = {foo::Test::Test<T>}, decl\n"
+        "4: targets = {I}\n"
+        "5: targets = {I}, decl\n"
+        "6: targets = {foo::Test}\n"
+        "7: targets = {I}\n"
+        "8: targets = {foo::Test}\n"
+        "9: targets = {I}\n"
+        "10: targets = {}, qualifier = 'I::'\n"}};
 
   for (const auto &C : Cases) {
     llvm::StringRef ExpectedCode = C.first;
-- 
2.11.0