[analsysis_server] Fix missing types on record fields in LSP completion detail

Fixes Dart-Code/Dart-Code#4788

Change-Id: Iaa57a5e486dac6c1978b8576b4855f8c3e8955f8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/330107
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/lsp/mapping.dart

@@ -398,7 +398,10 @@ CompletionDetail getCompletionDetail(
 }) {
   final element = suggestion.element;
   var parameters = element?.parameters;
-  var returnType = element?.returnType;
+  // Prefer the element return type (because it's available for things like
+  // overrides) but fall back to the suggestion if there isn't one (to handle
+  // records).
+  var returnType = element?.returnType ?? suggestion.returnType;
 
   // Extract the type from setters to be shown in the place a return type
   // would usually be shown.

pkg/analysis_server/test/lsp/completion_dart_test.dart

@@ -598,6 +598,36 @@ bool a = ^
       detail: null,
     );
   }
+
+  Future<void> test_record() async {
+    final content = r'''
+void f((int, int) record) {
+  record.$^
+}
+''';
+
+    await expectLabels(content,
+        label: r'$1',
+        labelDetail: ' int',
+        labelDescription: null,
+        filterText: null,
+        detail: 'int');
+  }
+
+  Future<void> test_variable() async {
+    final content = r'''
+void f(int variable) {
+  varia^
+}
+''';
+
+    await expectLabels(content,
+        label: 'variable',
+        labelDetail: ' int',
+        labelDescription: null,
+        filterText: null,
+        detail: 'int');
+  }
 }
 
 @reflectiveTest