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https://issues.apache.org/jira/browse/GROOVY-12313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18129861#comment-18129861
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Paul King commented on GROOVY-12313:
------------------------------------

AI assessment:

bq. Classification: confirmed bug, triggered by non-hygienic AST from a 
third-party transform. Groovy has no rule against sharing expression nodes, but 
per-node metadata makes it fragile everywhere, not just here.
bq. Best immediate remedy is in Spock: create a fresh VariableExpression for 
each use. That's a few lines, fixes all released Groovy versions, and I'd 
suggest the reporter raise it with Spock.

It goes on to suggest some hardening on the Groovy side which I will look at.

> static-compilation leaks instanceof inferred type into else-branch
> ------------------------------------------------------------------
>
>                 Key: GROOVY-12313
>                 URL: https://issues.apache.org/jira/browse/GROOVY-12313
>             Project: Groovy
>          Issue Type: Bug
>    Affects Versions: 5.0.3, 4.0.31
>            Reporter: Björn Kautler
>            Priority: Major
>
> With this in groovyconsole.dev
> {code:java}
> @groovy.transform.CompileStatic
> class Foo extends Specification {
>    def foo() {
>       expect:
>          true
>       where:
>          [a, b] << [['a', 'b']]
>    }
> }
> {code}
> you get
> {code:java}
> Cannot cast object '[a, b]' with class 'java.util.ArrayList' to class 
> 'java.util.Map' due to: groovy.lang.GroovyRuntimeException: Could not find 
> matching constructor for: java.util.Map(String, String){code}
> The AST transformed code after class generation phase for this is
> {code:java}
>     @org.spockframework.runtime.model.DataProcessorMetadata(dataVariables = 
> ['a', 'b'])
>     public java.lang.Object $spock_feature_0_0proc(java.lang.Object 
> $spock_p0) {
>         java.lang.Object a = ((java.lang.Object) $spock_p0 instanceof 
> java.util.Map ? $spock_p0.getAt('a') : $spock_p0.getAt(0))
>         java.lang.Object b = ((java.lang.Object) $spock_p0 instanceof 
> java.util.Map ? $spock_p0.getAt('b') : $spock_p0.getAt(1))
>         return new java.lang.Object[]{ a , b }
>     } {code}
> where {{$spock_p0}} is given as {{{}['a', 'b']{}}}.
> Without static compilation this works fine and runs the expected iterations.
> With static compilation and indy switched off, the generated and then 
> decompiled bytecode is this:
> {code:java}
> @DataProcessorMetadata(
>     dataVariables = {"a", "b"}
> )
> public Object $spock_feature_0_0proc(Object $spock_p0) {
>     Object a = $spock_p0 instanceof Map ? 
> DefaultGroovyMethods.getAt((Map)ScriptBytecodeAdapter.castToType($spock_p0, 
> Map.class), "a") : 
> DefaultGroovyMethods.getAt((Map)ScriptBytecodeAdapter.castToType($spock_p0, 
> Map.class), 0);
>     Object b = $spock_p0 instanceof Map ? 
> DefaultGroovyMethods.getAt((Map)ScriptBytecodeAdapter.castToType($spock_p0, 
> Map.class), "b") : 
> DefaultGroovyMethods.getAt((Map)ScriptBytecodeAdapter.castToType($spock_p0, 
> Map.class), 1);
>     return new Object[]{a, b};
> } {code}
> So with static compilation the inferred {{Map}} type somehow leaks into the 
> else-branch of the ternary expression and causes this class-cast exception.



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