[PATCH] D108975: [clangd] Omit default template arguments from type hints

[Nathan Ridge via Phabricator via cfe-commits]

nridge created this revision.
nridge added a reviewer: kadircet.
Herald added subscribers: usaxena95, arphaman.
nridge requested review of this revision.
Herald added subscribers: cfe-commits, MaskRay, ilya-biryukov.
Herald added a project: clang-tools-extra.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D108975

Files:
  clang-tools-extra/clangd/InlayHints.cpp
  clang-tools-extra/clangd/unittests/InlayHintTests.cpp


Index: clang-tools-extra/clangd/unittests/InlayHintTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/InlayHintTests.cpp
+++ clang-tools-extra/clangd/unittests/InlayHintTests.cpp
@@ -602,6 +602,16 @@
   )cpp");
 }
 
+TEST(TypeHints, DefaultTemplateArgs) {
+  assertTypeHints(R"cpp(
+    template <typename, typename = int>
+    struct A {};
+    A<float> foo();
+    auto $var[[var]] = foo();
+  )cpp",
+                  ExpectedHint{": A<float>", "var"});
+}
+
 // FIXME: Low-hanging fruit where we could omit a type hint:
 //  - auto x = TypeName(...);
 //  - auto x = (TypeName) (...);
Index: clang-tools-extra/clangd/InlayHints.cpp
===================================================================
--- clang-tools-extra/clangd/InlayHints.cpp
+++ clang-tools-extra/clangd/InlayHints.cpp
@@ -24,7 +24,8 @@
       : Results(Results), AST(AST.getASTContext()),
         MainFileID(AST.getSourceManager().getMainFileID()),
         Resolver(AST.getHeuristicResolver()),
-        TypeHintPolicy(this->AST.getPrintingPolicy()) {
+        TypeHintPolicy(this->AST.getPrintingPolicy()),
+        StructuredBindingPolicy(this->AST.getPrintingPolicy()) {
     bool Invalid = false;
     llvm::StringRef Buf =
         AST.getSourceManager().getBufferData(MainFileID, &Invalid);
@@ -33,14 +34,16 @@
     TypeHintPolicy.SuppressScope = true; // keep type names short
     TypeHintPolicy.AnonymousTagLocations =
         false; // do not print lambda locations
-    // Print canonical types. Otherwise, SuppressScope would result in
-    // things like "metafunction<args>::type" being shorted to just "type",
-    // which is useless. This is particularly important for structured
-    // bindings that use the tuple_element protocol, where the non-canonical
-    // types would be "tuple_element<I, A>::type".
-    // Note, for "auto", we would often prefer sugared types, but the AST
-    // doesn't currently retain them in DeducedType anyways.
-    TypeHintPolicy.PrintCanonicalTypes = true;
+
+    // For structured bindings, print canonical types. This is important because
+    // for bindings that use the tuple_element protocol, the non-canonical types
+    // would be "tuple_element<I, A>::type".
+    // For "auto", we often prefer sugared types, but the AST doesn't currently
+    // retain them in DeducedType. However, not setting PrintCanonicalTypes for
+    // "auto" at least allows SuppressDefaultTemplateArgs (set by default) to
+    // have an effect.
+    StructuredBindingPolicy = TypeHintPolicy;
+    StructuredBindingPolicy.PrintCanonicalTypes = true;
   }
 
   bool VisitCXXConstructExpr(CXXConstructExpr *E) {
@@ -98,7 +101,8 @@
     // but show hints for the individual bindings.
     if (auto *DD = dyn_cast<DecompositionDecl>(D)) {
       for (auto *Binding : DD->bindings()) {
-        addTypeHint(Binding->getLocation(), Binding->getType(), ": ");
+        addTypeHint(Binding->getLocation(), Binding->getType(), ": ",
+                    StructuredBindingPolicy);
       }
       return true;
     }
@@ -327,11 +331,16 @@
   }
 
   void addTypeHint(SourceRange R, QualType T, llvm::StringRef Prefix) {
+    addTypeHint(R, T, Prefix, TypeHintPolicy);
+  }
+
+  void addTypeHint(SourceRange R, QualType T, llvm::StringRef Prefix,
+                   const PrintingPolicy &Policy) {
     // Do not print useless "NULL TYPE" hint.
     if (!T.getTypePtrOrNull())
       return;
 
-    std::string TypeName = T.getAsString(TypeHintPolicy);
+    std::string TypeName = T.getAsString(Policy);
     if (TypeName.length() < TypeNameLimit)
       addInlayHint(R, InlayHintKind::TypeHint, std::string(Prefix) + TypeName);
   }
@@ -342,6 +351,7 @@
   StringRef MainFileBuf;
   const HeuristicResolver *Resolver;
   PrintingPolicy TypeHintPolicy;
+  PrintingPolicy StructuredBindingPolicy;
 
   static const size_t TypeNameLimit = 32;
 };


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