https://issues.dlang.org/show_bug.cgi?id=22290
Issue ID: 22290
Summary: Disallow assignment to a non-elaborate field of an
rvalue
Product: D
Version: D2
Hardware: x86_64
OS: Linux
Status: NEW
Severity: enhancement
Priority: P1
Component: dmd
Assignee: [email protected]
Reporter: [email protected]
struct S{
int i;
}
S _s;
S s(){
return _s; //returns DUPLICATE of _s, not _s by reference
}
void main(){
s().i = 42; //new user might think _s.i is the variable that gets modified.
assert(!(_s.i == 42)); //They would be wrong.
}
Yes, there are valid cases when the rvalue DOES need to be mutated. However, in
cases like these, there are no side-effects, and the computation becomes
completely redundant, and the user finds out their error at runtime with no
proper diagnostic, since the program even successfully executes, not just
compiles.
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