[CodeCompletion] Signature help for braced constructor calls

Implementation is based on the "expected type" as used for
designated-initializers in braced init lists. This means it can deduce the type
in some cases where it's not written:

  void foo(Widget);
  foo({ /*help here*/ });

Only basic constructor calls are in scope of this patch, excluded are:
 - aggregate initialization (no help is offered for aggregates)
 - initializer_list initialization (no help is offered for these constructors)

Fixes https://github.com/clangd/clangd/issues/306

Differential Revision: https://reviews.llvm.org/D116317

1 files changed, 4 insertions, 2 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 0c1f88b..5900075 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -2420,7 +2420,8 @@ Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
     auto RunSignatureHelp = [&]() {
       QualType PreferredType = Actions.ProduceConstructorSignatureHelp(
           getCurScope(), ThisVarDecl->getType()->getCanonicalTypeInternal(),
-          ThisDecl->getLocation(), Exprs, T.getOpenLocation());
+          ThisDecl->getLocation(), Exprs, T.getOpenLocation(),
+          /*Braced=*/false);
       CalledSignatureHelp = true;
       return PreferredType;
     };
@@ -2440,7 +2441,8 @@ Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
       if (ThisVarDecl && PP.isCodeCompletionReached() && !CalledSignatureHelp) {
         Actions.ProduceConstructorSignatureHelp(
             getCurScope(), ThisVarDecl->getType()->getCanonicalTypeInternal(),
-            ThisDecl->getLocation(), Exprs, T.getOpenLocation());
+            ThisDecl->getLocation(), Exprs, T.getOpenLocation(),
+            /*Braced=*/false);
         CalledSignatureHelp = true;
       }
       Actions.ActOnInitializerError(ThisDecl);