[GROOVY-10959] Type checking fails when casting method references

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 03/Mar/23 15:57
• Updated: 15/Apr/23 15:54

Description

Probably related to GROOVY-10270.

I have the following program

import java.util.function.*;
import java.util.stream.*;


class Main {
  static final void test() {
    Foo<Object, String> x = null;
    Foo<String, String> y = null;
    BinaryOperator<String> z = null;

    final Object powdery = java.util.stream.Collectors.toConcurrentMap(
        x::m as Function<Object, String>,
        y::m as Function<String, String>,
        z
    );
  }
}

interface Foo<T1, T2> {
  T2 m(T1 x);
}

Actual behaviour

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 11: [Static type checking] - Cannot call <T,K,U> java.util.stream.Collectors#toConcurrentMap(java.util.function.Function<? super T, ? extends K>, java.util.function.Function<? super T, ? extends U>, java.util.function.BinaryOperator<U>) with arguments [java.util.function.Function<java.lang.Object, java.lang.String>, java.util.function.Function<java.lang.String, java.lang.String>, java.util.function.BinaryOperator<java.lang.String>]
 @ line 11, column 28.
       final Object powdery = java.util.stream.Collectors.toConcurrentMap(
                              ^

1 error

Expected behaviour

Compile successfully

Notes: If a remove type casts, the code compiles as expected.

Issue Links

• is related to: GROOVY-9998 Wildcards with a lower bound fail static type checking