[GROOVY-5746] Array assignment with operator does double call for index expression and array part

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.5, 2.3.0, 2.4.0-rc-1
• Fix Version/s: 4.0.0-beta-2
• Component/s: Static compilation
• Assignee: Eric Milles
• Reporter: Jochen Theodorou
• Created: 08/Oct/12 09:22
• Updated: 03/Feb/22 22:32
• Resolved: 20/Oct/21 19:59

Description

@groovy.transform.CompileStatic
class IndexTest {
    private int f = 0
    public int getIndex() {f++;0}
    def foo() {
        List<String> x = ["1","2"]
        x[index] += "1"
        assert x[0] == "11"
        assert f == 1
    }
}
def x = new IndexTest()
x.foo()

The program above shows code in which we use an operator in combination with array assignment and an index with a side effect. This code must run without calling getIndex() twice. Since the field f is incremented twice, this is not the case. Normal Groovy executed the code as wished. The probable implementation is x[index] = x[index] + "1", which not only evals index twice, but also x. x and index must be evaluated only once!