[clang-tools-extra] [clangd] Support go-to-definition on type hints. The core part (PR #86629)

[Younan Zhang via cfe-commits]

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@@ -1005,14 +1332,22 @@ class InlayHintVisitor : public RecursiveASTVisitor<InlayHintVisitor> {
     // The sugared type is more useful in some cases, and the canonical
     // type in other cases.
     auto Desugared = maybeDesugar(AST, T);
-    std::string TypeName = Desugared.getAsString(TypeHintPolicy);
-    if (T != Desugared && !shouldPrintTypeHint(TypeName)) {
+    std::vector<InlayHintLabelPart> Chunks;
+    TypeInlayHintLabelPartBuilder Builder(Desugared, AST, MainFilePath,
+                                          TypeHintPolicy, Prefix, Chunks);
+    Builder.Visit(Desugared.getTypePtr());
+    if (T != Desugared && !shouldPrintTypeHint(Chunks)) {
       // If the desugared type is too long to display, fallback to the sugared
       // type.
-      TypeName = T.getAsString(TypeHintPolicy);
+      Chunks.clear();
+      TypeInlayHintLabelPartBuilder Builder(T, AST, MainFilePath,
+                                            TypeHintPolicy, Prefix, Chunks);
+      Builder.Visit(T.getTypePtr());
     }
-    if (shouldPrintTypeHint(TypeName))
-      addInlayHint(R, HintSide::Right, InlayHintKind::Type, Prefix, TypeName,
+    if (shouldPrintTypeHint(Chunks))
+      addInlayHint(R, HintSide::Right, InlayHintKind::Type,
+                   /*Prefix=*/"", // We have handled prefixes in the builder.
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zyn0217 wrote:

I'm trying to put these prefixes i.e. ": " together with those unclickable type hints. i.e. to emit `: S` instead of adding such prefixes outside of the builder - we would end up copying the whole vector otherwise.

https://github.com/llvm/llvm-project/pull/86629