Issue 25095. Add 'Change X to Y type annotation' Quick Fix.

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

Index: pkg/analysis_server/lib/src/services/correction/fix_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
index eba635ff26ffc439c35e353eef55e1e949635319..f068b3bd1e5317403078091d4f23614afba7b6b5 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -292,6 +292,9 @@ class FixProcessor {
       _addFix_useStaticAccess_method();
       _addFix_useStaticAccess_property();
     }
+    if (errorCode == StaticTypeWarningCode.INVALID_ASSIGNMENT) {
+      _addFix_changeTypeAnnotation();
+    }
     if (errorCode == StaticTypeWarningCode.INVOCATION_OF_NON_FUNCTION) {
       _addFix_removeParentheses_inGetterInvocation();
     }
@@ -493,6 +496,29 @@ class FixProcessor {
     }
   }
 
+  void _addFix_changeTypeAnnotation() {
+    AstNode declaration = coveredNode.parent;
+    if (declaration is VariableDeclaration &&
+        declaration.initializer == coveredNode) {
+      AstNode variableList = declaration.parent;
+      if (variableList is VariableDeclarationList &&
+          variableList.variables.length == 1) {
+        TypeName typeNode = variableList.type;
+        if (typeNode != null) {
+          Expression initializer = coveredNode;
+          DartType newType = initializer.bestType;
+          if (newType is InterfaceType || newType is FunctionType) {
+            String newTypeSource =
+                utils.getTypeSource(newType, librariesToImport);
+            _addReplaceEdit(rf.rangeNode(typeNode), newTypeSource);
+            _addFix(DartFixKind.CHANGE_TYPE_ANNOTATION,
+                [typeNode.type.displayName, newTypeSource]);
+          }
+        }
+      }
+    }
+  }
+
   void _addFix_createClass() {
     Element prefixElement = null;
     String name = null;