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Fix Bugzilla Issue 24818 Sumtype with single-type wastes space #10642

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Merged
LightBender merged 3 commits into from
Feb 19, 2025
Merged

Fix Bugzilla Issue 24818 Sumtype with single-type wastes space #10642

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1214a69
Fix Bugzilla Issue 24818 Sumtype with single-type wastes space
Inkrementator Feb 18, 2025
d976e82
Move unittest to correct position
Inkrementator Feb 18, 2025
ca02a0e
Annotate unittest with @safe
Inkrementator Feb 18, 2025
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39 changes: 29 additions & 10 deletions std/sumtype.d
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Original file line number Diff line number Diff line change
Expand Up @@ -304,7 +304,10 @@ private:
}

Storage storage;
Tag tag;
static if (Types.length > 1)
Tag tag;
else
enum Tag tag = 0;

/* Accesses the value stored in a SumType by its index.
*
Expand Down Expand Up @@ -369,7 +372,8 @@ public:
storage.tupleof[tid] = forward!value;
}

tag = tid;
static if (Types.length > 1)
tag = tid;
}

static if (isCopyable!(const(T)))
Expand All @@ -380,7 +384,8 @@ public:
this(const(T) value) const
{
storage.tupleof[tid] = value;
tag = tid;
static if (Types.length > 1)
tag = tid;
}
}
}
Expand All @@ -397,7 +402,8 @@ public:
this(immutable(T) value) immutable
{
storage.tupleof[tid] = value;
tag = tid;
static if (Types.length > 1)
tag = tid;
}
}
}
Expand All @@ -415,7 +421,8 @@ public:
if (is(Value == DeducedParameterType!(inout(T))))
{
storage.tupleof[tid] = value;
tag = tid;
static if (Types.length > 1)
tag = tid;
}
}
}
Expand Down Expand Up @@ -449,7 +456,8 @@ public:
return newStorage;
});

tag = other.tag;
static if (Types.length > 1)
tag = other.tag;
}
}
else
Expand All @@ -469,7 +477,8 @@ public:
return newStorage;
});

tag = other.tag;
static if (Types.length > 1)
tag = other.tag;
}
}
else
Expand All @@ -493,7 +502,8 @@ public:
return newStorage;
});

tag = other.tag;
static if (Types.length > 1)
tag = other.tag;
}
}
else
Expand All @@ -517,7 +527,8 @@ public:
return newStorage;
});

tag = other.tag;
static if (Types.length > 1)
tag = other.tag;
}
}
else
Expand Down Expand Up @@ -644,7 +655,8 @@ public:
}

storage = newStorage;
tag = tid;
static if (Types.length > 1)
tag = tid;

return this;
}
Expand Down Expand Up @@ -1558,6 +1570,13 @@ version (D_BetterC) {} else
enum result = test();
}

// https://github.com/dlang/phobos/issues/10563
// Do not waste space for tag if sumtype has only single type
@safe unittest
{
static assert(SumType!int.sizeof == int.sizeof);
}

/// True if `T` is an instance of the `SumType` template, otherwise false.
private enum bool isSumTypeInstance(T) = is(T == SumType!Args, Args...);

Expand Down
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