Dario Bertini created GROOVY-7848:
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Summary: Closure generic parameters ignored and return types
missing from collections methods
Key: GROOVY-7848
URL: https://issues.apache.org/jira/browse/GROOVY-7848
Project: Groovy
Issue Type: Bug
Reporter: Dario Bertini
The theme of this ticket is type failures even specifying the correct input
parameter type in a Closure, specifically these 2 methods fail to compile with
CompileStatic/TypeChecked:
{{
@CompileStatic
static List foo(){
[[1,2], [3,4]].collect{List<Integer> pair -> pair[0]+pair[1]}
}
@CompileStatic
static bar(){
[[1, 3], [1, 2]].transpose().inject(true){acc, List pair -> acc
&& pair[0] == pair[1]}
}
}}
The first is due to the generic parameter Integer apparently being ignored.
bq. Error:(15, 48) Groovyc: [Static type checking] - Cannot find matching
method java.lang.Object#plus(java.lang.Object). Please check if the declared
type is right and if the method exists.
Ignoring it is just fine when compiling in Dynamic mode, but makes it
apparently impossible to write a similar Type Safe method
Apparently, this part of the language is as yet undocumented:
http://docs.groovy-lang.org/latest/html/documentation/index.html#generics
The second method instead, has a similar failure to locate Object#getAt(int),
but the actual error is this one:
bq. Error:(20, 50) Groovyc: Expected parameter of type java.lang.Object but got
java.util.List
Which is imho a bit unhelpful: I'm obviously passing it a List, at runtime...
and the the Closure parameter type is List, given that I would expect the error
to be the other way around: expected parameter of type List, but got Object
But the problem is not actually with Closure types, inference or the like... I
suspect it might simply be an imprecise type specified for transpose() result:
it should be List<List>, but is instead List (once I understood this I simply
created an intermedia variable with the explicit type as a workaround)
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