[GROOVY-9885] STC doesn't coerce GString in certain ternary expressions

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.0.7
• Fix Version/s: 3.0.8, 4.0.0-alpha-3, 2.5.16
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Christopher Smith
• Created: 08/Jan/21 01:47
• Updated: 01/Mar/22 21:25
• Resolved: 02/Mar/21 15:17

Description

I know there are a number of edge cases regarding automatic coercion from GString to String, so I'm not certain whether this is a specific case of a larger problem area, but I've been able to isolate it.

When using the named-parameter constructor approach, ternary expressions don't "inherit" the target type, and thus the inferred type of the expression is Serializable (not even CharSequence!). The problem is identical whether elvis or the long form is used.

@CompileStatic
class Elvis {
    static class HasString {
        String value
    }

    void foo(String a, String b, String c) {
        new HasString(
            value: (a ?: "$b $c")
        )
    }
}

Cannot assign value of type java.io.Serializable <? extends java.lang.Object> to variable of type java.lang.String

This doesn't fail when used as

new HasString().value =

An explicit as String makes everyone happy but shouldn't be needed.