remove prefer_bool_in_asserts (dart-archive/linter#4015)

Author: pq

lib/src/rules/prefer_bool_in_asserts.dart

@@ -2,10 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/visitor.dart';
-import 'package:analyzer/dart/element/type.dart';
-
 import '../analyzer.dart';
 
 const _desc = r'Prefer using a boolean as the assert condition.';
@@ -31,12 +27,6 @@ assert(() {
   return true;
 }());
 ```
-
-**DEPRECATED:** In Dart 2, `assert`s no longer accept  non-`bool` values so this
-rule is made redundant by the Dart analyzer's basic checks and is no longer
-necessary.
-
-The rule will be removed in a future Linter release.
 ''';
 
 class PreferBoolInAsserts extends LintRule {
@@ -50,45 +40,9 @@ class PreferBoolInAsserts extends LintRule {
             name: 'prefer_bool_in_asserts',
             description: _desc,
             details: _details,
-            state: State.deprecated(),
+            state: State.removed(since: dart3),
             group: Group.style);
 
   @override
   LintCode get lintCode => code;
-
-  @override
-  void registerNodeProcessors(
-      NodeLintRegistry registry, LinterContext context) {
-    var visitor = _Visitor(this, context);
-    registry.addAssertStatement(this, visitor);
-  }
-}
-
-class _Visitor extends SimpleAstVisitor<void> {
-  final LintRule rule;
-
-  final TypeSystem typeSystem;
-
-  final DartType boolType;
-
-  _Visitor(this.rule, LinterContext context)
-      : typeSystem = context.typeSystem,
-        boolType = context.typeProvider.boolType;
-
-  @override
-  void visitAssertStatement(AssertStatement node) {
-    var conditionType = _unbound(node.condition.staticType);
-    if (conditionType != null &&
-        !typeSystem.isAssignableTo(conditionType, boolType)) {
-      rule.reportLint(node.condition);
-    }
-  }
-
-  DartType? _unbound(DartType? type) {
-    var t = type;
-    while (t is TypeParameterType) {
-      t = t.bound;
-    }
-    return t;
-  }
 }