[PATCH] D133664: [clangd] Fix hover on symbol introduced by using declaration

[Tom Praschan via Phabricator via cfe-commits]

tom-anders created this revision.
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tom-anders requested review of this revision.
Herald added subscribers: cfe-commits, MaskRay, ilya-biryukov.
Herald added a project: clang-tools-extra.

This fixes https://github.com/clangd/clangd/issues/1284. The example
there was C++20's "using enum", but I noticed that we had the same issue
for other using-declarations.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133664

Files:
  clang-tools-extra/clangd/Hover.cpp
  clang-tools-extra/clangd/unittests/HoverTests.cpp


Index: clang-tools-extra/clangd/unittests/HoverTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/HoverTests.cpp
+++ clang-tools-extra/clangd/unittests/HoverTests.cpp
@@ -1630,6 +1630,26 @@
             HI.Type = "int";
             HI.Definition = "int foo";
           }},
+      {
+          R"cpp(// Function definition via using declaration
+            namespace ns { 
+              void foo(); 
+            }
+            int main() {
+              using ns::foo;
+              ^[[foo]]();
+            }
+          )cpp",
+          [](HoverInfo &HI) {
+            HI.Name = "foo";
+            HI.Kind = index::SymbolKind::Function;
+            HI.NamespaceScope = "ns::";
+            HI.Type = "void ()";
+            HI.Definition = "void foo()";
+            HI.Documentation = "";
+            HI.ReturnType = "void";
+            HI.Parameters = std::vector<HoverInfo::Param>{};
+          }},
       {
           R"cpp(// Macro
             #define MACRO 0
@@ -1734,6 +1754,25 @@
             HI.Definition = "ONE";
             HI.Value = "0";
           }},
+      {
+          R"cpp(// C++20's using enum
+            enum class Hello {
+              ONE, TWO, THREE,
+            };
+            void foo() {
+              using enum Hello;
+              Hello hello = [[O^NE]];
+            }
+          )cpp",
+          [](HoverInfo &HI) {
+            HI.Name = "ONE";
+            HI.Kind = index::SymbolKind::EnumConstant;
+            HI.NamespaceScope = "";
+            HI.LocalScope = "Hello::";
+            HI.Type = "enum Hello";
+            HI.Definition = "ONE";
+            HI.Value = "0";
+          }},
       {
           R"cpp(// Enumerator in anonymous enum
             enum {
Index: clang-tools-extra/clangd/Hover.cpp
===================================================================
--- clang-tools-extra/clangd/Hover.cpp
+++ clang-tools-extra/clangd/Hover.cpp
@@ -1082,10 +1082,22 @@
       auto Decls = explicitReferenceTargets(N->ASTNode, DeclRelation::Alias,
                                             AST.getHeuristicResolver());
       if (!Decls.empty()) {
-        HI = getHoverContents(Decls.front(), PP, Index, TB);
+        // For using-declarations, e.g.
+        //     namespace ns { void foo(); }
+        //     void bar() { using ns::foo; f^oo(); }
+        // The first declaration in Decls will refer to the using declaration,
+        // which isn't really useful for Hover. So check if we have something
+        // better, which in this example would be the actual declaration of foo.
+        auto *DeclToUse = Decls.begin();
+        while (llvm::isa<BaseUsingDecl>(*DeclToUse) &&
+               std::next(DeclToUse) != Decls.end()) {
+          ++DeclToUse;
+        }
+
+        HI = getHoverContents(*DeclToUse, PP, Index, TB);
         // Layout info only shown when hovering on the field/class itself.
-        if (Decls.front() == N->ASTNode.get<Decl>())
-          addLayoutInfo(*Decls.front(), *HI);
+        if (*DeclToUse == N->ASTNode.get<Decl>())
+          addLayoutInfo(**DeclToUse, *HI);
         // Look for a close enclosing expression to show the value of.
         if (!HI->Value)
           HI->Value = printExprValue(N, AST.getASTContext());


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