[jira] [Created] (GROOVY-10049) STC fails when calling a generic method from another generic method

["Lyuben Atanasov (Jira)" <ji...@apache.org>]

Lyuben Atanasov created GROOVY-10049:
----------------------------------------

             Summary: STC fails when calling a generic method from another generic method
                 Key: GROOVY-10049
                 URL: https://issues.apache.org/jira/browse/GROOVY-10049
             Project: Groovy
          Issue Type: Bug
          Components: Static Type Checker
    Affects Versions: 4.0.0-alpha-3, 3.0.8
         Environment: OpenJDK 8
            Reporter: Lyuben Atanasov


The static type checker fails to properly determine the return type of a generic method when that method is called from another generic method. Here's an example:
{code}
class Test {

	<T extends Number> Set<T> generateNumbers(Class<T> numberType) {
		// mock return value, needed to demonstrate the issue
		return Collections.emptySet();
	}

	<T extends Number> void printNumbers(Class<T> numberType) {
		generateNumbers(numberType).stream()
			.filter(num -> num.doubleValue() > 0)
			.forEach(num -> println "$num");
	}
	
}
{code}
With static type checking enabled, compilation of this class fails:
{noformat}
Script_bbf0c00c9b2872d2a3528c2d80bbaa49.groovy: 10: [Static type checking] - Cannot find matching method java.lang.Object#doubleValue(). Please check if the declared type is correct and if the method exists.
 @ line 10, column 19.
   			.filter(num -> num.doubleValue() > 0)
{noformat}

If we call the {{generateNumbers()}} method with a specific, everything works:
{code}
class Test {

	<T extends Number> Set<T> generateNumbers(Class<T> numberType) {
		return Collections.emptySet();
	}

	void printNumbers() {
		generateNumbers(Integer).stream()
			.filter(num -> num.doubleValue() > 0)
			.forEach(num -> println "$num");
	}
	
}
{code}

It looks like the static type checker does not properly take into account the generic types of the surrounding method and thus fails to determine the type of the returned value.



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