Support tear-off completions for named params (in constructors) (flutter-intellij#836)

pkg/analysis_server/lib/src/services/completion/dart/optype.dart

Index: pkg/analysis_server/lib/src/services/completion/dart/optype.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/optype.dart b/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
index 975e9107a6a3b1b10071758beb25929651fd09de..08cc0ba4a2ab865ee6eb4032457791c3eaa8ea64 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
@@ -14,6 +14,7 @@ import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/token.dart';
+import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 
 typedef int SuggestionsFilter(DartType dartType, int relevance);
@@ -730,6 +731,25 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor {
         }
       };
       optype.includeTypeNameSuggestions = true;
+
+      // Check for named parameters in constructor calls.
+      AstNode grandparent = node.parent.parent;
+      if (grandparent is ConstructorReferenceNode) {
+        ConstructorElement element =
+            (grandparent as ConstructorReferenceNode).staticElement;
+        List<ParameterElement> parameters = element.parameters;
+        ParameterElement parameterElement = parameters.firstWhere((e) {
+          if (e is DefaultFieldFormalParameterElementImpl) {
+            return e.field.name == node.name.label.name;
+          }
+          return e.parameterKind == ParameterKind.NAMED &&
+              e.name == node.name.label.name;
+        }, orElse: () => null);
+        // Suggest tear-offs.
+        if (parameterElement?.type is FunctionType) {
+          optype.includeVoidReturnSuggestions = true;
+        }
+      }
     }
   }