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https://issues.apache.org/jira/browse/GROOVY-12729?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul King updated GROOVY-12729:
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Summary: groovy-contracts: loop @Invariant and @Decreases are silently
disabled by {} or a qualified class literal; @Decreases({ [] }) can never pass;
simple class names in loop annotations are never resolved (was:
groovy-contracts: @Decreases is silently disabled by {} or by a qualified class
literal, rejects { [] } on every loop, and rejects a simple class name only
because it is never resolved)
> groovy-contracts: loop @Invariant and @Decreases are silently disabled by {}
> or a qualified class literal; @Decreases({ [] }) can never pass; simple class
> names in loop annotations are never resolved
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12729
> URL: https://issues.apache.org/jira/browse/GROOVY-12729
> Project: Groovy
> Issue Type: Bug
> Components: groovy-contracts
> Reporter: Paul King
> Priority: Major
>
> Probed on master (715553465f). Each loop runs 3 times. The results are the
> same in a script and in a class method.
> h3. 1. An empty closure or a qualified class literal turns off the check
> ||Annotation on the loop||Result||
> |{{@Invariant(\{\})}}|runs; no check is made, and nothing reports that|
> |{{@Invariant(java.lang.Object)}}|runs; no check is made|
> |{{@Decreases(\{\})}}|runs; no check is made, even on a loop that does not
> decrease|
> |{{@Decreases(java.lang.Object)}}|runs; no check is made|
> Controls: {{@Invariant(\{ i < 2 \})}} throws {{LoopInvariantViolation}}, and
> {{@Decreases(\{ n \})}} on a loop that does not decrease throws
> {{LoopVariantViolation: loop variant did not decrease: was 3, now 3}}.
> {{LoopInvariantASTTransformation}} and {{LoopVariantASTTransformation}}
> return without reporting anything in either case: when the value is not a
> closure, or when the closure has no expression.
> Class-level contracts already reject an empty closure. {{@Invariant(\{\})}}
> on a class fails to compile with:
> {noformat}
> [groovy-contracts] Annotation does not contain any expressions (e.g. use
> '@Requires({ argument1 })').
> {noformat}
> The loop forms should behave the same.
> h3. 2. {{@Decreases(\{ [] \})}} can never pass
> It throws {{LoopVariantViolation: loop variant did not decrease: was [], now
> []}} on every loop that runs more than once, including one that does decrease
> {{n}}. An empty tuple never decreases, so a compile error would be more
> helpful.
> {{@Invariant(\{ [] \})}} also always fails, but that is correct, since an
> empty list is false in Groovy, as with {{\{ false \}}}. Class-level
> {{@Invariant(\{ [] \})}} behaves the same way.
> h3. 3. Simple class names in loop annotations are never resolved
> ||Annotation on the loop||Result||
> |{{@Invariant(Object)}}, {{@Decreases(Object)}}|{{Only classes, closures, and
> method references can be used for attribute 'value' in
> @groovy.contracts.Invariant}} (or {{Decreases}})|
> |{{@Invariant(java.lang.Object)}}, {{@Decreases(java.lang.Object)}}|compiles,
> and is then silently ignored (see 1)|
> |{{@Invariant(Object.class)}}, {{@Decreases(Object.class)}}|{{unable to find
> class 'Object.class' for annotation attribute constant}}|
> So the simple name is rejected only by accident. An AST probe at CONVERSION,
> SEMANTIC_ANALYSIS and CANONICALIZATION shows the {{@Decreases(Object)}}
> member staying a {{VariableExpression(Object)}} throughout. A qualified name
> becomes a {{ClassExpression}} during SEMANTIC_ANALYSIS, and on a method
> annotation, {{@Requires(Object)}} becomes a {{ClassExpression}} as expected.
> This affects any annotation on a loop, not just contracts.
> A list value ({{@Invariant(['i < 2'])}}, {{@Decreases([1])}}) is correctly
> rejected by the generic annotation check.
> h3. Suggested fix
> * Loop {{@Invariant}} and {{@Decreases}}: report an error for a value that is
> not a closure, and for an empty closure, as class-level contracts do. Also
> report one for {{@Decreases(\{ [] \})}}.
> * Resolve class names in loop-statement annotations the same way as in
> declaration annotations (possibly a separate issue).
> Related: GROOVY-12128 (where loop contract checks fire), GROOVY-12723
> (@Modifies), and the issue raised alongside this one (class literals on
> @Requires, @Ensures and @Invariant).
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