groovy

Support multiple labels on the same statement

Details

  • Type: Improvement Improvement
  • Status: Open Open
  • Priority: Major Major
  • Resolution: Unresolved
  • Affects Version/s: 1.6-rc-1
  • Fix Version/s: 4.0
  • Component/s: Compiler, parser-antlr
  • Labels:
    None
  • Number of attachments :
    1

Description

Unlike Java, Groovy doesn't support multiple labels on the same statement - instead, the AST builder discards all but the first (!) label:

class MultipleLabels {
static void main(args) {
label1:
label2:
while (true)

{ break label1 // OK break label2 // Compile error: "break to missing label" }


}
}

For a discussion see: http://www.nabble.com/Multiple-labels-on-the-same-statement-td21543898.html

Activity

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Peter Niederwieser added a comment -

Here is a trivial patch to retain the last label instead of the first one, which is already an improvement. For 1.6.1 we can maybe do even better and have full support for multiple labels.

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Peter Niederwieser added a comment - Here is a trivial patch to retain the last label instead of the first one, which is already an improvement. For 1.6.1 we can maybe do even better and have full support for multiple labels.
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Guillaume Laforge added a comment -

Peter, haven't you made that change, I don't recall?

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Guillaume Laforge added a comment - Peter, haven't you made that change, I don't recall?
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Peter Niederwieser added a comment -

I did apply the trivial patch. What I didn't do is to add true support for multiple labels, because the simple solution I had in mind didn't work.

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Peter Niederwieser added a comment - I did apply the trivial patch. What I didn't do is to add true support for multiple labels, because the simple solution I had in mind didn't work.
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Guillaume Laforge added a comment -

So what should we do about this issue? Close it? Keep it?

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Guillaume Laforge added a comment - So what should we do about this issue? Close it? Keep it?
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Peter Niederwieser added a comment -

Should we tweak the parser s.t. multiple labels on the same statement result in a syntax error? That's certainly better than silently dropping labels.

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Peter Niederwieser added a comment - Should we tweak the parser s.t. multiple labels on the same statement result in a syntax error? That's certainly better than silently dropping labels.
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Guillaume Laforge added a comment -

Btw, what does Java do in this regard?

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Guillaume Laforge added a comment - Btw, what does Java do in this regard?
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Peter Niederwieser added a comment -

Java does allow multiple labels on the same statement (checked both the spec and Sun's implementation).

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Peter Niederwieser added a comment - Java does allow multiple labels on the same statement (checked both the spec and Sun's implementation).
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Guillaume Laforge added a comment -

Okay, so we should be consistent here, and follow the Java lead by allowing multiple labels too.
So let's keep the issue open for the moment.

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Guillaume Laforge added a comment - Okay, so we should be consistent here, and follow the Java lead by allowing multiple labels too. So let's keep the issue open for the moment.
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Peter Niederwieser added a comment -

In my opinion, supporting multiple labels isn't worth it for Groovy, at least not for 1.x. What seems more important is to prevent the silent dropping of labels (i.e. to be honest about what we currently support). This should be a simple fix that doesn't require any changes to the grammar or AST.

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Peter Niederwieser added a comment - In my opinion, supporting multiple labels isn't worth it for Groovy, at least not for 1.x. What seems more important is to prevent the silent dropping of labels (i.e. to be honest about what we currently support). This should be a simple fix that doesn't require any changes to the grammar or AST.

People

  • Assignee:
    Unassigned
    Reporter:
    Peter Niederwieser
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Dates

  • Created:
    Updated: