Only render inlay hints after variable bindings

Use a document symbols query to figure out where variable bindings are
located, then only render the inlay hints there.

Author: fwcd

Sources/SourceKitLSP/Swift/SwiftLanguageServer.swift

@@ -1058,27 +1058,44 @@ extension SwiftLanguageServer {
 
   public func inlayHints(_ req: Request<InlayHintsRequest>) {
     let uri = req.params.textDocument.uri
-    expressionTypeInfos(uri) { result in
-      switch result {
-      case .success(let infos):
-        let hints = infos
-          .lazy
-          .map { info in
-            InlayHint(
-              position: info.range.upperBound,
-              category: .type,
-              label: info.printedType
-            )
-          }
-          .filter { hint in
-            // TODO: Compute inlay hints only for the requested range/categories
-            // instead of filtering them afterwards.
-            (req.params.range?.contains(hint.position) ?? true)
-            && (hint.category.flatMap { req.params.only?.contains($0) } ?? true)
+    documentSymbols(uri) { symbolsResult in
+      do {
+        func bindings(_ symbols: [DocumentSymbol]) -> [DocumentSymbol] {
+          symbols
+            .flatMap { bindings($0.children ?? []) + ($0.kind == .variable ? [$0] : []) }
+        }
+
+        let symbols = try symbolsResult.get()
+        let bindingPositions = Set(bindings(symbols).map { $0.range.upperBound })
+
+        self.expressionTypeInfos(uri) { infosResult in
+          do {
+            let infos = try infosResult.get()
+            let hints = infos
+              .lazy
+              .filter { bindingPositions.contains($0.range.upperBound) }
+              .map { info in
+                InlayHint(
+                  position: info.range.upperBound,
+                  category: .type,
+                  label: info.printedType
+                )
+              }
+              .filter { hint in
+                // TODO: Compute inlay hints only for the requested range/categories
+                // instead of filtering them afterwards.
+                (req.params.range?.contains(hint.position) ?? true)
+                && (hint.category.flatMap { req.params.only?.contains($0) } ?? true)
+              }
+            req.reply(.success(Array(hints)))
+          } catch {
+            let message = "expression types for inlay hints failed for \(uri): \(error)"
+            log(message, level: .warning)
+            req.reply(.failure(.unknown(message)))
           }
-        req.reply(.success(Array(hints)))
-      case .failure(let error):
-        let message = "inlay hints failed \(uri): \(error)"
+        }
+      } catch {
+        let message = "document symbols for inlay hints failed for \(uri): \(error)"
         log(message, level: .warning)
         req.reply(.failure(.unknown(message)))
       }