[GROOVY-6241] Type inference fails for methods returning generic map types

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.1.5
• Fix Version/s: 2.1.8, 2.2.0
• Component/s: Static compilation, Static Type Checker
• Assignee: Jochen Theodorou
• Reporter: Rob Fletcher
• Created: 08/Jul/13 05:04
• Updated: 14/Oct/13 16:53
• Resolved: 10/Sep/13 08:02

Description

The static type checker rejects the last of the 4 assignments in the following code:

@groovy.transform.CompileStatic
class Foo {
    static void main(String... args) {
        List<Integer> list = [1, 2, 3]
        List<Integer> immutableList = [1, 2, 3].asImmutable()
        Map<String, Integer> map = [foo: 123, bar: 456]
        Map<String, Integer> immutableMap = [foo: 123, bar: 456].asImmutable()
    }
}

with the error Incompatible generic argument types. Cannot assign java.util.Map <java.lang.Object, java.lang.Object> to: java.util.Map <String, Integer>.

The generic signature on asImmutable should be sufficient for type inference to work (as it does for the list in the 2nd assignment).