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Type.fixTo: Always propagate the naked type to new variants #22852

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Merged
dlang-bot merged 1 commit into from
Apr 2, 2026
+31 −21
Merged

Type.fixTo: Always propagate the naked type to new variants #22852

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4 changes: 4 additions & 0 deletions compiler/src/dmd/mtype.d
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Original file line number Diff line number Diff line change
Expand Up @@ -404,6 +404,10 @@ extern (C++) abstract class Type : ASTNode
* we bank on the idea that usually only one of variants exist.
* It will also speed up code because these are rarely referenced and
* so need not be in the cache.
*
* NOTE: The cache stores the naked type at the "identity" position.
* For example, a "shared const T" type will have its naked "T" type
* in the field "scto". See also: dmd.typesem.nakedOf(Type).
*/
Type cto; // MODFlags.const_
Type ito; // MODFlags.immutable_
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48 changes: 27 additions & 21 deletions compiler/src/dmd/typesem.d
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Expand Up @@ -464,57 +464,62 @@ void check(Type _this)
* For our new type '_this', which is type-constructed from t,
* fill in the cto, ito, sto, scto, wto shortcuts.
*/
void fixTo(Type _this, Type t)
private void fixTo(Type _this, Type t)
{
Type mto = null; // the naked type of `t`
if (_this.mod || t.mod)
{
_this.getMcache();
t.getMcache();
}
// If fixing this: immutable(T*) by t: immutable(T)*,
// cache t to this.xto won't break transitivity.
Type mto = null;
Type tn = _this.nextOf();
if (!tn || _this.ty != Tsarray && tn.mod == t.nextOf().mod)
{
switch (t.mod)
{
case 0:
mto = t;
mto = t; // t is naked
break;

case MODFlags.const_:
_this.getMcache();
mto = t.mcache.cto; // cto is naked
_this.mcache.cto = t;
break;

case MODFlags.wild:
_this.getMcache();
mto = t.mcache.wto; // wto is naked
_this.mcache.wto = t;
break;

case MODFlags.wildconst:
_this.getMcache();
mto = t.mcache.wcto; // wcto is naked
_this.mcache.wcto = t;
break;

case MODFlags.shared_:
_this.getMcache();
mto = t.mcache.sto; // sto is naked
_this.mcache.sto = t;
break;

case MODFlags.shared_ | MODFlags.const_:
_this.getMcache();
mto = t.mcache.scto; // scto is naked
_this.mcache.scto = t;
break;

case MODFlags.shared_ | MODFlags.wild:
_this.getMcache();
mto = t.mcache.swto; // swto is naked
_this.mcache.swto = t;
break;

case MODFlags.shared_ | MODFlags.wildconst:
_this.getMcache();
mto = t.mcache.swcto; // swcto is naked
_this.mcache.swcto = t;
break;

case MODFlags.immutable_:
_this.getMcache();
mto = t.mcache.ito; // ito is naked
_this.mcache.ito = t;
break;

Expand All @@ -524,11 +529,6 @@ void fixTo(Type _this, Type t)
}
assert(_this.mod != t.mod);

if (_this.mod)
{
_this.getMcache();
t.getMcache();
}
switch (_this.mod)
{
case 0:
Expand Down Expand Up @@ -8529,6 +8529,15 @@ Type immutableOf(Type type)

/********************************
* Make type mutable.
* 0 => 0
* const => 0
* immutable => 0
* shared => shared
* shared const => shared
* wild => 0
* wild const => 0
* shared wild => shared
* shared wild const => shared
*/
Type mutableOf(Type type)
{
Expand All @@ -8545,15 +8554,12 @@ Type mutableOf(Type type)
type.getMcache();
if (type.isShared())
{
if (type.isWild())
t = type.mcache.swcto; // shared wild const -> shared
else
t = type.mcache.sto; // shared const => shared
t = type.mcache.sto; // shared (wild) const => shared
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@ibuclaw ibuclaw Apr 1, 2026 •
edited
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Found bug. The swcto back reference of a shared-wild-const type is "naked", not "shared".

It has never been used to hold the reference to the "shared" type, that is in sto instead.

}
else
{
if (type.isWild())
t = type.mcache.wcto; // wild const -> naked
t = type.mcache.wcto; // wild const => naked
else
t = type.mcache.cto; // const => naked
}
Expand Down
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