[GROOVY-10272] Wrong inference when using ternary operator with lambdas

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0.0-alpha-3, 4.0.0-beta-1, 3.0.9
• Fix Version/s: 4.0.5, 3.0.20
• Component/s: Static compilation, Static Type Checker
• Assignee: Eric Milles
• Reporter: Stefanos Chaliasos
• Created: 29/Sep/21 08:34
• Updated: 30/Nov/23 16:48
• Resolved: 19/May/22 17:49

Description

I have the following Groovy program.

import java.util.function.Function;

@groovy.transform.TypeChecked
class Main {
    public static final void main() {
        Function<Long, Double> x
        // Works
        if (true) {
            x = {Long a -> (Double) a}
        } else {
            x = {Long b -> (Double) b}
        }
        // Fails
        Function<Long, Double> y = ((true) ? {Long a -> (Double) a} : {Long b -> (Double) b})
    }
}

Actual Behavior

The program does not compile, and I get the following error.

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Main.groovy: 16: [Static type checking] - Cannot assign value of type java.lang.Double to variable of type java.util.function.Function<java.lang.Long, java.lang.Double>
 @ line 16, column 36.
           Function<Long, Double> y = ((true) ? {Long a -> (Double) a} : {Long b -> (Double) b})
                                      ^

1 error

Note that the computed type is the return type of the lambdas.

Expected Behavior

Compile successfully.

Comment

Tested against 4-beta-1, 4-alpha-3, 3.0.9, and master (commit: b26dbbeabe1e3d27d30c936701b1a571e24d5ab2). Maybe similar to GROOVY-10271.

Issue Links

• relates to: GROOVY-10701 NullPointerException in instruction selection phase when having conditionals with lambdas and function references