[jira] [Created] (GROOVY-10306) STC rejects program when assigning a closure that returns a class field

[Thodoris Sotiropoulos (Jira)]

Thodoris Sotiropoulos created GROOVY-10306:
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             Summary: STC rejects program when assigning a closure that returns 
a class field
                 Key: GROOVY-10306
                 URL: https://issues.apache.org/jira/browse/GROOVY-10306
             Project: Groovy
          Issue Type: Bug
          Components: Static Type Checker
            Reporter: Thodoris Sotiropoulos


I have the following program

{code:java}
import java.util.function.Supplier;

class Main {
    byte x = 1;

    void foo() {
        Supplier<Number> y =  () -> x;
        
    }
}
{code}

h3. Actual behaviour
{code}
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Main.java: 8: [Static type checking] - Incompatible generic argument types. 
Cannot assign java.util.function.Supplier<java.lang.Byte> to: 
java.util.function.Supplier<java.lang.Number>
 @ line 8, column 31.
           Supplier<Number> y =  () -> x;
                                 ^

1 error
{code}

h3. Expected behaviour
Compile successfully

Note that if `x` is a local variabled defined in function `foo`, groovyc 
compiles the program successfully.

Tested against master



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