https://issues.dlang.org/show_bug.cgi?id=17729
Issue ID: 17729
Summary: dmd says cast expression is "not an lvalue", but it
can be used as one in other contexts
Product: D
Version: D2
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P1
Component: dmd
Assignee: [email protected]
Reporter: [email protected]
As requested by Andrei on GitHub
(<https://github.com/dlang/druntime/pull/1605#discussion_r131770687>).
Taking the address of a cast expression gets rejected:
----
struct S { int field = 0; }
void main()
{
shared S s;
auto p = & cast(S) s;
/* Error: cast(S)s is not an lvalue */
}
----
But we can take the address of the field and it's the same as `s`'s:
----
struct S { int field = 0; }
void main()
{
shared S s;
auto p = &(cast(S) s).field;
*p = 1;
assert(s.field == 1);
}
----
We can even use the cast expression on the left-hand side of an assignment:
----
struct S { int field = 0; }
void main()
{
shared S s;
cast(S) s = S(1); /* no error */
assert(s.field == 1); /* passes */
}
----
Either all snippets should be rejected, or they should all be accepted.
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