[GROOVY-10601] Incompatible generic argument type when combining conditionals and bounded type parameters

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.11, 4.0.3
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 28/Apr/22 10:55
• Updated: 24/Jul/22 12:16
• Resolved: 18/May/22 14:58

Description

I have the following program

class Foo<X> {}

class Test {

  public static <T extends Foo<Number>> T test() {
    T x = (T) null;
    T y = (true) ? x : (T) null;
    y
  }
}

Actual behaviour

The compiler rejects the program with

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 8: [Static type checking] - Incompatible generic argument types. Cannot assign Foo<java.lang.Object> to: T
 @ line 8, column 5.
       y
       ^

1 error

Expected behaviour

Compile successfully

*NOTE:* This bug occurs only when `test` and `Foo` have type parameters with different names.

Tested against master (commit: 5c468cd352f37fb5c599a3f51534ffcc55b339ed).

Issue Links

• is related to: GROOVY-10363 STC produces compile-time error on encoutering bounded type parameter with conditional