Revert "[analyzer] new warning for nullable '==' parameter type"

This reverts commit 48ee1f2.

Reason for revert: flutter/flutter#118632

Original change's description:
> [analyzer] new warning for nullable '==' parameter type
>
> This rule checks that a parameter to an `operator ==` implementation has
> a non-nullable type.
>
> I intentionally did not enforce, in this rule, that the parameter is
> exactly `Object`. It is legal to narrow the parameter type to a
> different non-nullable type, like `int`. I can't imagine doing it, but
> it seems to be unrelated to whether the type should be nullable or not.
>
> Fixes https://github.com/dart-lang/linter/issues/3441
>
> Replaces dart-archive/linter#3923
>
> Change-Id: I61d4a7b1ab8318dc9403da1633c352de95bfac61
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/277700
> Reviewed-by: Mark Zhou <[email protected]>
> Commit-Queue: Samuel Rawlins <[email protected]>
> Reviewed-by: Brian Wilkerson <[email protected]>

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I6f96936b8d4e785b5f8e9719751e4b61c2a6ca2a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/279141
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Siva Annamalai <[email protected]>
Reviewed-by: Mark Zhou <[email protected]>
Reviewed-by: Phil Quitslund <[email protected]>

Author: Kaushik Iska

pkg/_fe_analyzer_shared/lib/src/parser/identifier_context_impl.dart

@@ -447,7 +447,7 @@ class ExtensionShowHideElementIdentifierContext extends IdentifierContext {
   }
 
   @override
-  bool operator ==(Object other) {
+  bool operator ==(dynamic other) {
     return other is ExtensionShowHideElementIdentifierContext &&
         _kind == other._kind;
   }

pkg/analysis_server/lib/src/services/correction/error_fix_status.yaml

@@ -27,7 +27,7 @@
 # - 655 "needsEvaluation"
 #   - 282 for CompileTimeErrorCodes
 #   - 220 for ParserErrorCodes
-# -  93 "needsFix"
+# -  92 "needsFix"
 # - 310 "hasFix"
 # -  94 "noFix"
 
@@ -2755,11 +2755,6 @@ StaticWarningCode.INVALID_NULL_AWARE_OPERATOR_AFTER_SHORT_CIRCUIT:
   status: hasFix
 StaticWarningCode.MISSING_ENUM_CONSTANT_IN_SWITCH:
   status: hasFix
-StaticWarningCode.NON_NULLABLE_EQUALS_PARAMETER:
-  status: needsFix
-  notes: |-
-    The fix is to remove the question mark if the parameter has one (if the
-    written type is an alias, it may not).
 StaticWarningCode.SDK_VERSION_AS_EXPRESSION_IN_CONST_CONTEXT:
   status: hasFix
 StaticWarningCode.SDK_VERSION_ASYNC_EXPORTED_FROM_CORE:

pkg/analysis_server/test/src/services/correction/fix/remove_comparison_test.dart

@@ -281,7 +281,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) =>
+  operator ==(Object? other) =>
           other != null &&
           other is Person &&
           name == other.name;
@@ -292,7 +292,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) =>
+  operator ==(Object? other) =>
           other is Person &&
           name == other.name;
 }
@@ -305,7 +305,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) {
+  operator ==(Object? other) {
     return other != null &&
           other is Person &&
           name == other.name;
@@ -317,7 +317,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) {
+  operator ==(Object? other) {
     return other is Person &&
           name == other.name;
   }
@@ -331,7 +331,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) {
+  operator ==(Object? other) {
     if (other is! Person) return false;
     other ??= Person();
     return other.name == name;
@@ -349,7 +349,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) {
+  operator ==(Object? other) {
     if (other is! Person) return false;
     final toCompare = other ?? Person();
     return toCompare.name == name;
@@ -362,7 +362,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) {
+  operator ==(Object? other) {
     if (other is! Person) return false;
     final toCompare = other;
     return toCompare.name == name;
@@ -381,7 +381,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) {
+  operator ==(Object? other) {
     if (other == null) return false;
     return other is Person &&
           name == other.name;
@@ -393,7 +393,7 @@ class Person {
   final String name = '';
 
   @override
-  operator ==(Object other) {
+  operator ==(Object? other) {
     return other is Person &&
           name == other.name;
   }

pkg/analysis_server/tool/code_completion/metrics_util.dart

@@ -458,7 +458,7 @@ class Place {
   int get rank => _numerator;
 
   @override
-  bool operator ==(Object other) =>
+  bool operator ==(dynamic other) =>
       other is Place &&
       _numerator == other._numerator &&
       _denominator == other._denominator;

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

@@ -683,7 +683,6 @@ class BestPracticesVerifier extends RecursiveAstVisitor<void> {
       _checkForMissingReturn(node.body, node);
       _mustCallSuperVerifier.checkMethodDeclaration(node);
       _checkForUnnecessaryNoSuchMethod(node);
-      _checkForNullableEqualsParameterType(node);
 
       var name = Name(_currentLibrary.source.uri, element.name);
       var elementIsOverride = element is ClassMemberElement &&
@@ -1391,44 +1390,6 @@ class BestPracticesVerifier extends RecursiveAstVisitor<void> {
     }
   }
 
-  void _checkForNullableEqualsParameterType(MethodDeclaration node) {
-    if (!_typeSystem.isNonNullableByDefault) {
-      // Cannot specify non-nullable types before null safety.
-      return;
-    }
-
-    if (node.name.type != TokenType.EQ_EQ) {
-      return;
-    }
-
-    var parameters = node.parameters;
-    if (parameters == null) {
-      return;
-    }
-
-    if (parameters.parameters.length != 1) {
-      return;
-    }
-
-    var parameter = parameters.parameters.first;
-    var parameterElement = parameter.declaredElement;
-    if (parameterElement == null) {
-      return;
-    }
-
-    var type = parameterElement.type;
-    if (!type.isDartCoreObject && !type.isDynamic) {
-      // There is no legal way to define a nullable parameter type, which is not
-      // `dynamic` or `Object?`, so avoid double reporting here.
-      return;
-    }
-
-    if (_typeSystem.isNullable(parameterElement.type)) {
-      _errorReporter.reportErrorForToken(
-          StaticWarningCode.NON_NULLABLE_EQUALS_PARAMETER, node.name);
-    }
-  }
-
   void _checkForNullableTypeInCatchClause(CatchClause node) {
     if (!_isNonNullableByDefault) {
       return;

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

@@ -5645,14 +5645,6 @@ class StaticWarningCode extends AnalyzerErrorCode {
     hasPublishedDocs: true,
   );
 
-  ///  No parameters.
-  static const StaticWarningCode NON_NULLABLE_EQUALS_PARAMETER =
-      StaticWarningCode(
-    'NON_NULLABLE_EQUALS_PARAMETER',
-    "The parameter type of '==' operators should be non-nullable.",
-    correctionMessage: "Try using a non-nullable type.",
-  );
-
   ///  Parameters:
   ///  0: the name of the class
   static const StaticWarningCode SDK_VERSION_ASYNC_EXPORTED_FROM_CORE =

pkg/analyzer/lib/src/error/error_code_values.g.dart

@@ -965,7 +965,6 @@ const List<ErrorCode> errorCodeValues = [
   StaticWarningCode.INVALID_NULL_AWARE_OPERATOR,
   StaticWarningCode.INVALID_NULL_AWARE_OPERATOR_AFTER_SHORT_CIRCUIT,
   StaticWarningCode.MISSING_ENUM_CONSTANT_IN_SWITCH,
-  StaticWarningCode.NON_NULLABLE_EQUALS_PARAMETER,
   StaticWarningCode.SDK_VERSION_ASYNC_EXPORTED_FROM_CORE,
   StaticWarningCode.SDK_VERSION_AS_EXPRESSION_IN_CONST_CONTEXT,
   StaticWarningCode.SDK_VERSION_BOOL_OPERATOR_IN_CONST_CONTEXT,

pkg/analyzer/messages.yaml

@@ -5643,7 +5643,7 @@ CompileTimeErrorCode:
 
       ```dart
       mixin M on Enum {
-        bool operator [!==!](Object other) => false;
+        bool operator [!==!](Object? other) => false;
       }
       ```
 
@@ -22797,11 +22797,6 @@ StaticWarningCode:
       ```
       TODO(brianwilkerson) This documentation will need to be updated when NNBD
        ships.
-  NON_NULLABLE_EQUALS_PARAMETER:
-    problemMessage: "The parameter type of '==' operators should be non-nullable."
-    correctionMessage: Try using a non-nullable type.
-    hasPublishedDocs: false
-    comment: No parameters.
   SDK_VERSION_ASYNC_EXPORTED_FROM_CORE:
     problemMessage: "The class '{0}' wasn't exported from 'dart:core' until version 2.1, but this code is required to be able to run on earlier versions."
     correctionMessage: "Try either importing 'dart:async' or updating the SDK constraints."

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

@@ -28,18 +28,18 @@ extension E on String {
   test_instance_sameKind() async {
     await assertErrorsInCode('''
 extension E on String {
-  bool operator==(Object _) => false;
+  bool operator==(_) => false;
   int get hashCode => 0;
   String toString() => '';
   dynamic get runtimeType => null;
   dynamic noSuchMethod(_) => null;
 }
 ''', [
       error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 39, 2),
-      error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 72, 8),
-      error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 96, 8),
-      error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 128, 11),
-      error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 159, 12),
+      error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 65, 8),
+      error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 89, 8),
+      error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 121, 11),
+      error(CompileTimeErrorCode.EXTENSION_DECLARES_MEMBER_OF_OBJECT, 152, 12),
     ]);
   }