lib/src/rules/prefer_typing_uninitialized_variables.dart

// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
// 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 '../analyzer.dart';

const _desc = r'Prefer typing uninitialized variables and fields.';

const _details = r'''

**PREFER** specifying a type annotation for uninitialized variables and fields.

Forgoing type annotations for uninitialized variables is a bad practice because
you may accidentally assign them to a type that you didn't originally intend to.

**BAD:**
```
class BadClass {
  static var bar; // LINT
  var foo; // LINT

  void method() {
    var bar; // LINT
    bar = 5;
    print(bar);
  }
}
```

**BAD:**
```
void aFunction() {
  var bar; // LINT
  bar = 5;
  ...
}
```

**GOOD:**
```
class GoodClass {
  static var bar = 7;
  var foo = 42;
  int baz; // OK

  void method() {
    int baz;
    var bar = 5;
    ...
  }
}
```

''';

class PreferTypingUninitializedVariables extends LintRule
    implements NodeLintRule {
  PreferTypingUninitializedVariables()
      : super(
            name: 'prefer_typing_uninitialized_variables',
            description: _desc,
            details: _details,
            group: Group.style);

  @override
  void registerNodeProcessors(
      NodeLintRegistry registry, LinterContext context) {
    final visitor = _Visitor(this);
    registry.addVariableDeclarationList(this, visitor);
  }
}

class _Visitor extends SimpleAstVisitor<void> {
  final LintRule rule;

  _Visitor(this.rule);

  @override
  void visitVariableDeclarationList(VariableDeclarationList node) {
    if (node.type != null) {
      return;
    }

    node.variables.forEach((v) {
      if (v.initializer == null) {
        rule.reportLint(v);
      }
    });
  }
}