[jira] [Created] (GROOVY-10623) Type mismatch when encountering unconditional flow typing and null

[Thodoris Sotiropoulos (Jira)]

Thodoris Sotiropoulos created GROOVY-10623:
----------------------------------------------

             Summary: Type mismatch when encountering unconditional flow typing 
and null
                 Key: GROOVY-10623
                 URL: https://issues.apache.org/jira/browse/GROOVY-10623
             Project: Groovy
          Issue Type: Bug
          Components: Static Type Checker
            Reporter: Thodoris Sotiropoulos


I don't know if this is a bug or a feature

I have the following program

{code}

class A {}

class Test {
  void test() {
    def x = new A() // type of x is A
    x = null; // type of x becomes Object

    A y = x
  }

  void test2() {
    def x = new A()
    if (true) {
      x = null
    }
    A y = x // compiles as expected

  }
}
{code}

h3. Actual behavior

{code}
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 9: [Static type checking] - Cannot assign value of type 
java.lang.Object to variable of type A
 @ line 9, column 11.
       A y = x
             ^

1 error
{code}

h3. Expected behavior

Compile successfully

The issue here is that when the compiler encounters a `null` assignment to a 
`def` variable, it changes the previously-inferred type of the variable to 
`Object`. Probably, this is not necessary as `null` is assignable to any type.

Tested against master (commit: ee12bb52381e8f0583c61fc25d43de1f55b80a87)



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