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digitalmars.D.bugs - [Issue 23088] New: spurious case of "`expression`" has no effect


          Issue ID: 23088
           Summary: spurious case of "`expression`" has no effect
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: diagnostic, rejects-valid
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: b2.temp gmx.com

For the following code

static int v;

extern(C) int rand();

ref int a()
    return v = rand();

int main()
    a == 0;
    return v ? 1 : 0;

we get, with -de, the output

 /tmp/temp_7F3C12CCD670.d:12:5: Error: `a() == 0` has no effect
but the effect of the call directly influences the return code of the program. The compiler, by digging in the nested expressions could determine that it contains one call to an impure function and consequently allow (or not warn) about the comparison. --
May 04 2022