[GROOVY-9953] Type from flow typing is not propagated in variable assignments

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.7, 4.0.0-alpha-2
• Fix Version/s: 3.0.8, 4.0.0-alpha-3, 2.5.19
• Component/s: Static compilation, Static Type Checker
• Assignee: Eric Milles
• Reporter: Stefanos Chaliasos
• Created: 24/Feb/21 18:57
• Updated: 26/Aug/22 20:07
• Resolved: 02/Mar/21 14:58

Description

I have the following Groovy program.

class A {}

@groovy.transform.CompileStatic
class Main {

  static A bar(Object x) {
    if (x instanceof A) {
      def y = x // Inferred Object and not A
      y
    } else {
      new A()
    }
  }
}

Actual Behavior

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

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Main.groovy: 9: [Static type checking] - Cannot return value of type java.lang.Object on method returning type A
 @ line 9, column 7.
         y
         ^

1 error

Expected Behavior

Compile successfully.

Affected Version

I have also tested it with the compiler from Master (commit: 444f6a5e7f10b75d43d94e7bb4fe771ae384c321).