[GROOVY-10280] Type variable substitution does not work well when running into chain of field accesses

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-beta-2, 2.5.17, 3.0.11
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 04/Oct/21 13:46
• Updated: 11/Mar/22 19:23
• Resolved: 10/Oct/21 15:40

Description

I have the following program

class Foo<T> {
  T foo() {
    new Bar<T>().f1.f2.f3;
  }
  
}

class Bar<Y> {
  Baz<Y> f1;
}

class Baz<T> {
  Qux<T> f2;
}

class Qux<X> {
  X f3;
}

Actual behavior

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 3: [Static type checking] - Cannot return value of type Y on method returning type T
 @ line 3, column 5.
       new Bar<T>().f1.f2.f3;
       ^

1 error

Expected behavior

Compile successfully

Tested against master (https://github.com/apache/groovy/commit/0e8d0e26e3fe4f8cc21d58f1a1163ae29a8892db)