null_check_on_nullable_type_parameter pattern assignment support (#4224)

* `null_check_on_nullable_type_parameter` pattern assignment support

* ++

* rework

Author: pq

lib/src/rules/null_check_on_nullable_type_parameter.dart

@@ -70,7 +70,7 @@ class NullCheckOnNullableTypeParameter extends LintRule {
 
     var visitor = _Visitor(this, context);
     registry.addPostfixExpression(this, visitor);
-    registry.addRecordPattern(this, visitor);
+    registry.addNullAssertPattern(this, visitor);
   }
 }
 
@@ -83,6 +83,13 @@ class _Visitor extends SimpleAstVisitor<void> {
   bool isNullableTypeParameterType(DartType? type) =>
       type is TypeParameterType && context.typeSystem.isNullable(type);
 
+  @override
+  void visitNullAssertPattern(NullAssertPattern node) {
+    if (isNullableTypeParameterType(node.matchedValueType)) {
+      rule.reportLintForToken(node.operator);
+    }
+  }
+
   @override
   void visitPostfixExpression(PostfixExpression node) {
     if (node.operator.type != TokenType.BANG) return;
@@ -97,16 +104,4 @@ class _Visitor extends SimpleAstVisitor<void> {
       rule.reportLintForToken(node.operator);
     }
   }
-
-  @override
-  void visitRecordPattern(RecordPattern node) {
-    for (var field in node.fields) {
-      var pattern = field.pattern;
-      if (pattern is NullAssertPattern) {
-        if (isNullableTypeParameterType(pattern.matchedValueType)) {
-          rule.reportLintForToken(pattern.operator);
-        }
-      }
-    }
-  }
 }

test/rules/null_check_on_nullable_type_parameter_test.dart

@@ -18,13 +18,73 @@ class NullCheckOnNullableTypeParameterTestLanguage300 extends LintRuleTest
   @override
   String get lintRule => 'null_check_on_nullable_type_parameter';
 
-  test_nullAssertPattern() async {
+  test_nullAssertPattern_ifCase() async {
     await assertDiagnostics(r'''
-void f<T>((T?, T?) p){
+f<T>(T? x){
+  if (x case var y!) print(y);
+}
+''', [
+      lint(30, 1),
+    ]);
+  }
+
+  test_nullAssertPattern_list() async {
+    await assertDiagnostics(r'''
+f<T>(List<T?> l){
+  var [x!, y] = l;
+}
+''', [
+      lint(26, 1),
+    ]);
+  }
+
+  @FailingTest(
+      reason: 'Exception raised in resolver',
+      issue: 'https://github.com/dart-lang/linter/issues/4258')
+  test_nullAssertPattern_logicalOr() async {
+    await assertDiagnostics(r'''
+f<T>(T? x){
+  switch(x) {
+    case var y! || y == 2 : print(y);
+  }
+}
+''', [
+      lint(39, 1),
+    ]);
+  }
+
+  test_nullAssertPattern_map() async {
+    await assertDiagnostics(r'''
+f<T>(Map<String, T?> m){
+  var {'x': y!} = m;
+}
+''', [
+      lint(38, 1),
+    ]);
+  }
+
+  test_nullAssertPattern_object() async {
+    await assertDiagnostics(r'''
+class A<E> {
+  E? a;
+  A(this.a);
+}
+
+f<T>(T? t, A<T> u) {
+  A(a: t!) = u;
+}
+''', [
+      lint(66, 1),
+    ]);
+  }
+
+  test_nullAssertPattern_record() async {
+    await assertDiagnostics(r'''
+f<T>((T?, T?) p){
   var (x!, y) = p;
 }
 ''', [
-      lint(31, 1),
+      lint(26, 1),
     ]);
   }
 }