compiler/java/com/google/dart/compiler/backend/js/JsFirstExpressionVisitor.java - Issue 9479013: Remove backends.

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Issue 9479013: Remove backends. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart

Patch Set: Created 8 years, 9 months ago

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« compiler/java/com/google/dart/compiler/CompilerConfiguration.java ('K') | « compiler/java/com/google/dart/compiler/backend/js/JsErrorCode.java ('k') | compiler/java/com/google/dart/compiler/backend/js/JsNameProvider.java » ('j') | compiler/java/com/google/dart/compiler/metrics/DartEventType.java » ('J')
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1 // Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file

2 // for details. All rights reserved. Use of this source code is governed by a

3 // BSD-style license that can be found in the LICENSE file.

4

5 package com.google.dart.compiler.backend.js;

6

7 import com.google.dart.compiler.backend.js.ast.JsArrayAccess;

8 import com.google.dart.compiler.backend.js.ast.JsArrayLiteral;

9 import com.google.dart.compiler.backend.js.ast.JsBinaryOperation;

10 import com.google.dart.compiler.backend.js.ast.JsConditional;

11 import com.google.dart.compiler.backend.js.ast.JsContext;

12 import com.google.dart.compiler.backend.js.ast.JsExprStmt;

13 import com.google.dart.compiler.backend.js.ast.JsExpression;

14 import com.google.dart.compiler.backend.js.ast.JsFunction;

15 import com.google.dart.compiler.backend.js.ast.JsInvocation;

16 import com.google.dart.compiler.backend.js.ast.JsNameRef;

17 import com.google.dart.compiler.backend.js.ast.JsNew;

18 import com.google.dart.compiler.backend.js.ast.JsObjectLiteral;

19 import com.google.dart.compiler.backend.js.ast.JsPostfixOperation;

20 import com.google.dart.compiler.backend.js.ast.JsPrefixOperation;

21 import com.google.dart.compiler.backend.js.ast.JsRegExp;

22 import com.google.dart.compiler.backend.js.ast.JsVisitor;

23

24 /**

25 * Determines if an expression statement needs to be surrounded by parentheses.

26 *

27 * The statement or the left-most expression needs to be surrounded by

28 * parentheses if the left-most expression is an object literal or a function

29 * object. Function declarations do not need parentheses.

30 *

31 * For example the following require parentheses:<br>

32 * <ul>

33 * <li>{ key : 'value'}</li>

34 * <li>{ key : 'value'}.key</li>

35 * <li>function () {return 1;}()</li>

36 * <li>function () {return 1;}.prototype</li>

37 * </ul>

38 *

39 * The following do not require parentheses:<br>

40 * <ul>

41 * <li>var x = { key : 'value'}</li>

42 * <li>"string" + { key : 'value'}.key</li>

43 * <li>function func() {}</li>

44 * <li>function() {}</li>

45 * </ul>

46 */

47 public class JsFirstExpressionVisitor extends JsVisitor {

48

49 public static boolean exec(JsExprStmt statement) {

50 JsFirstExpressionVisitor visitor = new JsFirstExpressionVisitor();

51 JsExpression expression = statement.getExpression();

52 // Pure function declarations do not need parentheses

53 if (expression instanceof JsFunction) {

54 return false;

55 }

56 visitor.accept(statement.getExpression());

57 return visitor.needsParentheses;

58 }

59

60 private boolean needsParentheses = false;

61

62 private JsFirstExpressionVisitor() {

63 }

64

65 @Override

66 public boolean visit(JsArrayAccess x, JsContext ctx) {

67 accept(x.getArrayExpr());

68 return false;

69 }

70

71 @Override

72 public boolean visit(JsArrayLiteral x, JsContext ctx) {

73 return false;

74 }

75

76 @Override

77 public boolean visit(JsBinaryOperation x, JsContext ctx) {

78 accept(x.getArg1());

79 return false;

80 }

81

82 @Override

83 public boolean visit(JsConditional x, JsContext ctx) {

84 accept(x.getTestExpression());

85 return false;

86 }

87

88 @Override

89 public boolean visit(JsFunction x, JsContext ctx) {

90 needsParentheses = true;

91 return false;

92 }

93

94 @Override

95 public boolean visit(JsInvocation x, JsContext ctx) {

96 accept(x.getQualifier());

97 return false;

98 }

99

100 @Override

101 public boolean visit(JsNameRef x, JsContext ctx) {

102 if (!x.isLeaf()) {

103 accept(x.getQualifier());

104 }

105 return false;

106 }

107

108 @Override

109 public boolean visit(JsNew x, JsContext ctx) {

110 return false;

111 }

112

113 @Override

114 public boolean visit(JsObjectLiteral x, JsContext ctx) {

115 needsParentheses = true;

116 return false;

117 }

118

119 @Override

120 public boolean visit(JsPostfixOperation x, JsContext ctx) {

121 accept(x.getArg());

122 return false;

123 }

124

125 @Override

126 public boolean visit(JsPrefixOperation x, JsContext ctx) {

127 return false;

128 }

129

130 @Override

131 public boolean visit(JsRegExp x, JsContext ctx) {

132 return false;

133 }

134 }

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