[llvm-branch-commits] [clang-tools-extra] [clangd] Show type hint for simple cases of dependent 'auto' (PR #156284)

[Nathan Ridge via llvm-branch-commits]

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@@ -633,13 +633,30 @@ class InlayHintVisitor : public RecursiveASTVisitor<InlayHintVisitor> {
     }
 
     if (auto *AT = D->getType()->getContainedAutoType()) {
-      if (AT->isDeduced() && !D->getType()->isDependentType()) {
-        // Our current approach is to place the hint on the variable
-        // and accordingly print the full type
-        // (e.g. for `const auto& x = 42`, print `const int&`).
-        // Alternatively, we could place the hint on the `auto`
-        // (and then just print the type deduced for the `auto`).
-        addTypeHint(D->getLocation(), D->getType(), /*Prefix=*/": ");
+      if (AT->isDeduced()) {
+        QualType T;
+        // If the type is dependent, HeuristicResolver *may* be able to
+        // resolve it to something that's useful to print. In other
+        // cases, it can't, and the resultng type would just be printed
+        // as "<dependent type>", in which case don't hint it at all.
+        if (D->getType()->isDependentType()) {
+          if (D->hasInit()) {
+            QualType Resolved = Resolver->resolveExprToType(D->getInit());
+            if (Resolved != AST.DependentTy) {
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HighCommander4 wrote:

`TemplateTypeParmType` returns true for `isDependentType()`, so it would cause us to not issue a hint in the example from the previous comment.

https://github.com/llvm/llvm-project/pull/156284