Array dup ignores copy constructor with qualified argument · Issue #17212 · dlang/dmd (original) (raw)

Paul Backus (@pbackus) reported this on 2024-03-08T15:15:00Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=24432

Description

As of DMD 2.107.1, the following program fails to compile:

struct S { int* dummy; this(ref immutable S) {} }

void main() { immutable(S) s1; S s2 = s1; // ok

auto arr1 = [immutable(S)()];
auto arr2 = arr1.dup; // error

}

The error message is:

bug.d(13): Error: none of the overloads of template object.dup are callable using argument types !()(immutable(S)[]) /usr/include/dmd/druntime/import/object.d(3007): Candidates are: dup(T : V[K], K, V)(T aa) /usr/include/dmd/druntime/import/object.d(3045): dup(T : V[K], K, V)(T* aa) /usr/include/dmd/druntime/import/object.d(3835): dup(T)(T[] a) with T = immutable(S) must satisfy the following constraint: !is(const(T) : T) /usr/include/dmd/druntime/import/object.d(3858): dup(T)(const(T)[] a) with T = S must satisfy the following constraint: is(const(T) : T)

dup should be able to create a mutable copy of an immutable S using the appropriately-qualified copy constructor. However, it fails to do so, because its template constraint is too strict.

This bug was originally reported in issue 20879.