Thodoris Sotiropoulos created GROOVY-10480:
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Summary: Closure that assigns null to object changes the type of
variable
Key: GROOVY-10480
URL: https://issues.apache.org/jira/browse/GROOVY-10480
Project: Groovy
Issue Type: Bug
Components: Static Type Checker
Reporter: Thodoris Sotiropoulos
I have the following Groovy program
{code:java}
class Foo {
void foo() {}
}
class Main {
static void bar() {
def x = new Foo();
if (false) {
x = null;
}
x.foo(); // works
}
static void baz() {
def x = new Foo();
def clos = { -> {
x = null;
}}
x.foo(); // fails
}
}
{code}
h3. Actual behaviour
The assignment that takes inside closure changes the type of variable `x`, even
though closure is never being called.
The compilerthen rejects the program by raising the following error message.
{code}
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 22: [Static type checking] - A closure shared variable [x] has
been assigned with various types and the method [foo()] does not exist in the
lowest upper bound of those types: [java.lang.Object]. In general, this is a
bad practice (variable reuse) because the compiler cannot determine safely what
is the type of the variable at the moment of the call in a multithreaded
context.
@ line 22, column 5.
x.foo();
^
1 error
{code}
h3. Expected behaviour
Compile successfully
Tested against master
(https://github.com/apache/groovy/commit/5601ea14304b67e71586b0196e38f90fa1a46f5b).
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