RFR: 8289397: Fix warnings: Possible accidental assignment in place of a comparison. A condition expression should not be reduced to an assignment

[Andy Goryachev]

On Tue, 26 Jul 2022 21:14:58 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

> - replaced with exact functional equivalent (in the presence of exceptions, for example)

I think the warning serves a good purpose of preventing a bug, it also offloads thinking to the compiler.

At the same time, the byte code emitted by two variants is identical, i.e.:

source

`public int accidental(int x)
    {
        boolean rv;
        if(rv = (x == 0)) {
            return 1;
        }
        return 2;
    }
    
    public int explicit(int x)
    {
        boolean rv;
        if((rv = (x == 0)) == true) {
            return 1;
        }
        return 2;
    }`

byte code:

`public int accidental(int);
    Code:
       0: iload_1
       1: ifne          8
       4: iconst_1
       5: goto          9
       8: iconst_0
       9: dup
      10: istore_2
      11: ifeq          16
      14: iconst_1
      15: ireturn
      16: iconst_2
      17: ireturn`

public int explicit(int);
    Code:
       0: iload_1
       1: ifne          8
       4: iconst_1
       5: goto          9
       8: iconst_0
       9: dup
      10: istore_2
      11: ifeq          16
      14: iconst_1
      15: ireturn
      16: iconst_2
      17: ireturn`

I don't know why github can't create a code block normally... sorry.

-------------

PR: https://git.openjdk.org/jfx/pull/851