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fix: align Lua 5.2 numeric coercion and math selection #380

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Merged
akeit0 merged 2 commits into from
Oct 27, 2026
Merged

fix: align Lua 5.2 numeric coercion and math selection #380

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bb83114
fix: align Lua 5.2 VM comparisons and numeric operators
akeit0 Oct 27, 2026
8aa7108
fix: align numeric coercion and math selection with Lua 5.2
akeit0 Oct 27, 2026
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22 changes: 17 additions & 5 deletions src/Lua/LuaValue.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -361,13 +361,18 @@ bool TryParseToDouble(out double result)
}

var str = Unsafe.As<string>(referenceValue!);
var span = str.AsSpan().Trim();
if (span.Length == 0)
var span = str.AsSpan();
if (!span.IsEmpty && (span[0] <= ' ' || span[^1] <= ' '))
span = span.Trim(" \f\n\r\t\v");
// .NET's parser accepts trailing NULs, Unicode whitespace and named
// infinities/NaNs. A Lua numeral must end with a hex digit or decimal point.
if (span.Length == 0 || !(StringHelper.IsDigit(span[^1]) || span[^1] == '.'))
{
result = default!;
return false;
}

var numberText = span;
var sign = 1;
var first = span[0];
if (first is '+')
Expand All @@ -381,6 +386,12 @@ bool TryParseToDouble(out double result)
span = span[1..];
}

if (span.IsEmpty || !(span[0] is >= '0' and <= '9' or '.'))
{
result = default;
return false;
}

if (span.Length > 2 && span[0] is '0' && span[1] is 'x' or 'X')
{
// TODO: optimize
Expand All @@ -399,7 +410,7 @@ bool TryParseToDouble(out double result)
else
{
return double.TryParse(
str,
numberText,
NumberStyles.Float,
CultureInfo.InvariantCulture,
out result
Expand Down Expand Up @@ -769,8 +780,9 @@ CancellationToken cancellationToken
var count = await LuaVirtualMachine.Call(state, top, top, cancellationToken);
var result = count > 0 ? stack.Get(top) : Nil;
stack.SetTop(top + 1);
// Return one value, padding missing results and discarding extras.
stack.FastGet(top) = result;
// Lua 5.2 converts a numeric __tostring result to text.
stack.FastGet(top) =
result.Type == LuaValueType.Number ? new LuaValue(result.ToString()) : result;
return 1;
}
catch
Expand Down
63 changes: 47 additions & 16 deletions src/Lua/Runtime/LuaVirtualMachine.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -810,6 +810,21 @@ out doRestart
continue;
}

// Lua 5.2 only invokes __eq for tables/userdata of the
// same type. Primitive inequality needs no slow-path call.
if (
vb.Type != vc.Type
|| vb.Type is not (LuaValueType.Table or LuaValueType.UserData)
)
{
if (iA == 1)
{
context.Pc++;
}

continue;
}

if (
ExecuteCompareOperationMetaMethod(
vb,
Expand Down Expand Up @@ -950,7 +965,7 @@ out doRestart
var step = Unsafe.Add(ref indexRef, 2).UnsafeReadDouble();
var index = indexRef.UnsafeReadDouble() + step;

if (step >= 0 ? index <= limit : limit <= index)
if (step > 0 ? index <= limit : limit <= index)
{
context.Pc += instruction.SBx;
indexRef = index;
Expand Down Expand Up @@ -1128,13 +1143,9 @@ OpCode opcode
[MethodImpl(MethodImplOptions.NoInlining)]
internal static double Mod(double a, double b)
{
var mod = a % b;
if ((b > 0 && mod < 0) || (b < 0 && mod > 0))
{
mod += b;
}

return mod;
// Lua 5.2 uses this expression, including its floating-point rounding.
// A sign-adjusted remainder differs for values such as 5 and 0.1.
return a - (Math.Floor(a / b) * b);
}

static void SelfPostOperation(
Expand Down Expand Up @@ -2810,6 +2821,32 @@ CancellationToken cancellationToken
}
}

static bool TryGetCompareMetamethod(
LuaGlobalState state,
LuaValue left,
LuaValue right,
string name,
out LuaValue metamethod
)
{
if (name == Metamethods.Eq)
{
metamethod = default;
return left.Type == right.Type
&& left.Type is LuaValueType.Table or LuaValueType.UserData
&& state.TryGetMetatable(left, out var leftMetatable)
&& leftMetatable.TryGetValue(name, out metamethod)
&& state.TryGetMetatable(right, out var rightMetatable)
&& (
leftMetatable == rightMetatable
|| rightMetatable.TryGetValue(name, out var other) && metamethod == other
);
}

return left.TryGetMetamethod(state, name, out metamethod)
|| right.TryGetMetamethod(state, name, out metamethod);
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool ExecuteCompareOperationMetaMethod(
LuaValue vb,
Expand All @@ -2823,10 +2860,7 @@ out bool doRestart
doRestart = false;
var reverseLe = false;
ReCheck:
if (
vb.TryGetMetamethod(context.GlobalState, name, out var metamethod)
|| vc.TryGetMetamethod(context.GlobalState, name, out metamethod)
)
if (TryGetCompareMetamethod(context.GlobalState, vb, vc, name, out var metamethod))
{
var stack = context.Stack;
var newBase = stack.Count;
Expand Down Expand Up @@ -2959,10 +2993,7 @@ CancellationToken cancellationToken
var (name, description) = opCode.GetNameAndDescription();
var reverseLe = false;
ReCheck:
if (
vb.TryGetMetamethod(state.GlobalState, name, out var metamethod)
|| vc.TryGetMetamethod(state.GlobalState, name, out metamethod)
)
if (TryGetCompareMetamethod(state.GlobalState, vb, vc, name, out var metamethod))
{
var stack = state.Stack;
var top = stack.Count;
Expand Down
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