Make UNNECESSARY_NULL_AWARE_CALL a warning

Change-Id: I0cbe9522dcddb4c664ae5679e521191d0c91d777
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/106385
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Mike Fairhurst <[email protected]>

Author: MichaelRFairhurst

pkg/analyzer/lib/error/error.dart

@@ -369,7 +369,6 @@ const List<ErrorCode> errorCodeValues = const [
   HintCode.UNDEFINED_SHOWN_NAME,
   HintCode.UNNECESSARY_CAST,
   HintCode.UNNECESSARY_NO_SUCH_METHOD,
-  HintCode.UNNECESSARY_NULL_AWARE_CALL,
   HintCode.UNNECESSARY_TYPE_CHECK_FALSE,
   HintCode.UNNECESSARY_TYPE_CHECK_TRUE,
   HintCode.UNUSED_CATCH_CLAUSE,
@@ -693,6 +692,7 @@ const List<ErrorCode> errorCodeValues = const [
   StaticWarningCode.UNDEFINED_IDENTIFIER,
   StaticWarningCode.UNDEFINED_IDENTIFIER_AWAIT,
   StaticWarningCode.UNDEFINED_NAMED_PARAMETER,
+  StaticWarningCode.UNNECESSARY_NULL_AWARE_CALL,
   StaticWarningCode.UNNECESSARY_NULL_AWARE_SPREAD,
   StaticWarningCode.USE_OF_VOID_RESULT,
   StaticWarningCode.UNCHECKED_USE_OF_NULLABLE_VALUE,

pkg/analyzer/lib/src/dart/error/hint_codes.dart

@@ -803,15 +803,6 @@ class HintCode extends ErrorCode {
       'UNNECESSARY_NO_SUCH_METHOD', "Unnecessary 'noSuchMethod' declaration.",
       correction: "Try removing the declaration of 'noSuchMethod'.");
 
-  /**
-   * When the '?.' operator is used on a target that we know to be non-null,
-   * it is unnecessary.
-   */
-  static const HintCode UNNECESSARY_NULL_AWARE_CALL = const HintCode(
-      'UNNECESSARY_NULL_AWARE_CALL',
-      "The target expression cannot be null, and so '?.' is not necessary.",
-      correction: "Replace the '?.' with a '.' in the invocation.");
-
   /**
    * Unnecessary type checks, the result is always false.
    */

pkg/analyzer/lib/src/error/codes.dart

@@ -4931,6 +4931,15 @@ class StaticWarningCode extends ErrorCode {
               'Try changing the type, or casting, to a more useful type like'
               ' dynamic');
 
+  /**
+   * When the '?.' operator is used on a target that we know to be non-null,
+   * it is unnecessary.
+   */
+  static const StaticWarningCode UNNECESSARY_NULL_AWARE_CALL =
+      const StaticWarningCode('UNNECESSARY_NULL_AWARE_CALL',
+          "The target expression cannot be null, and so '?.' is not necessary.",
+          correction: "Replace the '?.' with a '.' in the invocation.");
+
   /**
    * It is a static warning to assign void to any non-void type in dart.
    * compile-time error). Report that error specially for a better user

pkg/analyzer/lib/src/generated/error_verifier.dart

@@ -5580,16 +5580,15 @@ class ErrorVerifier extends RecursiveAstVisitor<void> {
 
     ErrorCode errorCode;
     if (operator.type == TokenType.QUESTION_PERIOD) {
-      errorCode = HintCode.UNNECESSARY_NULL_AWARE_CALL;
+      errorCode = StaticWarningCode.UNNECESSARY_NULL_AWARE_CALL;
     } else if (operator.type == TokenType.PERIOD_PERIOD_PERIOD_QUESTION) {
       errorCode = StaticWarningCode.UNNECESSARY_NULL_AWARE_SPREAD;
     } else {
       return;
     }
 
     if (target.staticType != null &&
-        (target.staticType as TypeImpl).nullabilitySuffix ==
-            NullabilitySuffix.none) {
+        _typeSystem.isNonNullable(target.staticType)) {
       _errorReporter.reportErrorForToken(errorCode, operator, []);
     }
   }

pkg/analyzer/test/src/diagnostics/unnecessary_null_aware_call_test.dart

@@ -27,7 +27,7 @@ f(int x) {
   (x)?.isEven;
 }
 ''', [
-      error(HintCode.UNNECESSARY_NULL_AWARE_CALL, 16, 2),
+      error(StaticWarningCode.UNNECESSARY_NULL_AWARE_CALL, 16, 2),
     ]);
   }
 
@@ -45,7 +45,7 @@ f(int x) {
   x?.isEven;
 }
 ''', [
-      error(HintCode.UNNECESSARY_NULL_AWARE_CALL, 14, 2),
+      error(StaticWarningCode.UNNECESSARY_NULL_AWARE_CALL, 14, 2),
     ]);
   }
 
@@ -63,7 +63,7 @@ f(int x) {
   (x)?.round();
 }
 ''', [
-      error(HintCode.UNNECESSARY_NULL_AWARE_CALL, 16, 2),
+      error(StaticWarningCode.UNNECESSARY_NULL_AWARE_CALL, 16, 2),
     ]);
   }
 
@@ -81,7 +81,7 @@ f(int x) {
   x?.round();
 }
 ''', [
-      error(HintCode.UNNECESSARY_NULL_AWARE_CALL, 14, 2),
+      error(StaticWarningCode.UNNECESSARY_NULL_AWARE_CALL, 14, 2),
     ]);
   }
 

tests/language_2/nnbd/static_errors/nullable_function_types_test.dart

@@ -14,7 +14,7 @@ void main() {
   Function? nf2;
   C c1 = new C();
   C? nc1;
-  var nf3 = c1?.call;
+  var nf3 = nc1?.call;
   Object? object;