奇怪的 Eclipse AST 结果,带有内部枚举类

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英文:

Strange result of eclipse AST with inner enum class

问题

以下是翻译好的内容:

我正在尝试使用 Eclipse JDT AST 进行实验,但遇到了一个奇怪的行为,我找不到任何解释。

这是我的示例代码:

public static void main(String[] args) {
    StringBuilder content = new StringBuilder();
    content.append("class Foo {");
    content.append("    enum Bar {");
    content.append("        VALUE;");
    content.append("        int getValue() {");
    content.append("            return 4;");
    content.append("        }");
    content.append("    }");
    content.append("    int getValue() {");
    content.append("        return 42;");
    content.append("    }");
    content.append("}");

    ASTParser parser = ASTParser.newParser(AST.JLS13);
    parser.setKind(ASTParser.K_COMPILATION_UNIT);
    parser.setSource(content.toString().toCharArray());

    CompilationUnit astNode = (CompilationUnit) parser.createAST(null);

    Visitor rtVisitor = new Visitor();
    astNode.accept(rtVisitor);
}

private static class Visitor extends ASTVisitor {

    @Override
    public boolean visit(TypeDeclaration node) {
        System.out.println(node);
        return super.visit(node);
    }
}

正如你所见,我定义了一个非常简单的示例类,其中包含一个内部枚举类,两个类都具有相同签名的方法。

但奇怪的是,此代码的输出(即解析的 TypeDeclaration)是:

class Foo {
    enum Bar;
    {
    }
    int getValue(){
        return 4;
    }
    {
    }
    int getValue(){
        return 42;
    }
}

由某种原因,TypeDeclaration 的主体包括:

  1. FieldDeclarationenum Bar;
  2. Initializer{}
  3. MethodDeclarationint getValue(){ return 4; }
  4. 另一个 Initializer{}
  5. 另一个 MethodDeclarationint getValue(){ return 42; }

这导致我的实际代码抛出错误,因为看起来存在两个具有相同签名的方法。

为什么枚举不是实际的 EnumDeclaration,而是看起来枚举内部的方法实际上是在外部类中声明的?

我认为这不是一个 bug,因为 Eclipse 中的 AST 视图可以很好地处理类似的类,但我无法弄清楚我做错了什么。启用绑定解析也没有帮助。

英文:

I am experimenting with eclipse jdt AST and am running into a strange behaviour that I can find no explanation for.

Here is my example code:

public static void main(String[] args) {
	StringBuilder content = new StringBuilder();
	content.append("class Foo {");
	content.append("	enum Bar {");
	content.append("		VALUE;");
	content.append("		int getValue() {");
	content.append("			return 4;");
	content.append("		}");
	content.append("	}");
	content.append("	int getValue() {");
	content.append("		return 42;");
	content.append("	}");
	content.append("}");

	ASTParser parser = ASTParser.newParser(AST.JLS13);
	parser.setKind(ASTParser.K_COMPILATION_UNIT);
	parser.setSource(content.toString().toCharArray());

	CompilationUnit astNode = (CompilationUnit) parser.createAST(null);

	Visitor rtVisitor = new Visitor();
	astNode.accept(rtVisitor);

}

private static class Visitor extends ASTVisitor {

	@Override
	public boolean visit(TypeDeclaration node) {
		System.out.println(node);
		return super.visit(node);
	}
}

As you can see, I am defining a very simple example class that has an inner enum class where both classes have a method with the same signature.

Strangely though the output of this code (i.e. the parsed TypeDeclaration) is

class Foo {
  enum Bar;
{
  }
  int getValue(){
    return 4;
  }
{
  }
  int getValue(){
    return 42;
  }
}

For some reason, the body of the TypeDeclaration consists of:

  1. a FieldDeclaration: enum Bar;
  2. an Initializer: {}
  3. a MethodDeclaration: int getValue(){ return 4; }
  4. another Initializer: {}
  5. another MethodDeclaration: int getValue(){ return 42; }

This leads to my actual code throwing an error because it looks like there are two methods with identical signature.

Why am I not getting the enum as an actual EnumDeclaration with inner methods but rather it looks like the method inside the enum is actually declared in the outer class itself?

I do not think that this is a bug because the AST View in eclipse handles a similar class perfectly fine, but I cannot figure out what I am doing wrong. Enabling binding resolution did not help.

答案1

得分: 2

你需要通过调用 parser.setCompilerOptions 来设置编译器选项,以便正确处理源文件。<br>
由于你正在使用 enum 关键字,你至少需要使用 Java 5 兼容性:

ASTParser parser = ASTParser.newParser(AST.JLS13);
Map options = JavaCore.getOptions();
JavaCore.setComplianceOptions(JavaCore.VERSION_1_5, options);
parser.setCompilerOptions(options);
parser.setKind(ASTParser.K_COMPILATION_UNIT);
parser.setSource(content.toString().toCharArray());
英文:

You need to set compiler options by calling parser.setCompilerOptions, so that the source file is processed correctly.<br>
Since you are using the enum keyword, you need at least Java 5 compliance:

ASTParser parser = ASTParser.newParser(AST.JLS13);
Map options = JavaCore.getOptions();
JavaCore.setComplianceOptions(JavaCore.VERSION_1_5, options);
parser.setCompilerOptions(options);
parser.setKind(ASTParser.K_COMPILATION_UNIT);
parser.setSource(content.toString().toCharArray());

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  • 本文由 发表于 2020年10月6日 18:28:26
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