[GROOVY-10342] STC is unable to infer type parameter of parameterized method call

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.3
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 03/Nov/21 15:28
• Updated: 24/Jul/22 12:16
• Resolved: 19/May/22 15:55

Description

I have the following program

class A<T> {
  T f;
}

class Test {
  static <T> T m() { return null; }

  static <T extends Number> void test() {
    String x = m(); // works

    A<String> y = new A<>();
    y.f = m(); // works

    A<T> z = new A<T>();
    z.f = m(); // does not work
  }

}

Actual behaviour

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 15: [Static type checking] - Cannot assign value of type #T to variable of type T
 @ line 15, column 11.
       z.f = m();
             ^

1 error

Expected behavior

Compile successfully

NOTE: Replacing `T extends Number` with `T` compiles code successfully.

Tested against master.

Issue Links

• is related to: GROOVY-7316 CompileStatic cannot infer generic return type
• is related to: GROOVY-10067 STC: Wrong return value type inferred for generic method with upper bound without parameters
• is related to: GROOVY-10222 Unable to infer the type parameter of a parameterized function
• is related to: GROOVY-10256 STC: no error for incompatible type bounds on return value
• is related to: GROOVY-10324 STC is unable to infer type variable when combining parameterized types and the diamond operator