[Issue 1974] New: overloaded assignment operators work on non-lvalues

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=1974

           Summary: overloaded assignment operators work on non-lvalues
           Product: D
           Version: unspecified
          Platform: Other
        OS/Version: Other
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla at digitalmars.com
        ReportedBy: default_357-line at yahoo.de


Code:

module test; import std.stdio;
struct Foo { int y; void opAddAssign(int z) { y += z; } }
struct Bar { Foo fou; Foo test() { return fou; } }
void main() {
  Bar x;
  x.fou.y = 0;
  x.test() += 1337;
  writefln(x.fou.y);
}

The problem is that opAddAssign can be called even though the Foo it's being
called on is not an lvalue at all.

I see two solutions: either make this an error, or try to invoke opIndexAssign
to write the value back after the expression has been evaluated. The first is
probably easier.


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