Comptime fatal error

[disarray2077]

Introducing a new variable in Span<T> causes a fatal error during comptime evaluation:

---------------------------
FATAL ERROR
---------------------------
FATAL ERROR
Fatal Error in Module: __constEval
Function: ?Init@COMPTIME$?$SplitList@U_T0@@@Collections@System@bf@@CAXXZ
DbgLoc: @3 SplitList.bf:38:12
Malformed structure values in D:\BeefLang\Repository\Beef\IDEHelper\Backend\BeIRCodeGen.cpp:317

Tested with: ab31e5b

[bfiete]

Ah, yeah. It will definitely still be illegal, but I'll try to make the errors softer.

[kallisto56]

On latest nightly (cfd2bab) this is no longer crashes the IDE. Instead it results in ~60 strange errors.
For example:

ERROR: Method 'BfpFile_Seek' does not exist in type 'System.Platform.Hook'
       at line 14:25 in corlib\src\IO\FileStream.bf

Signature of BfpFile_Seek looks like this:

[CallingConvention(.Stdcall), CLink, StaticHook]
public static extern int64 BfpFile_Seek(BfpFile* file, int64 offset, BfpFileSeekKind seekKind);

By "strange" I mean that methods like BfpFile_Seek have no relation to Span<T>, at least on the surface.
Thankfully, first error in the list that will be printed out during attempt to build it, is about failed comptime, which does hints to user on where the problem may lie:

ERROR: Unable to comptime System.StaticHookAttribute.OnTypeInit(System.Type type, System.StaticHookAttribute* prev) at line 70:3 in ...\corlib\src\Platform.bf
  [StaticHook(typeof(SelfOuter))]
  > Access violation in comptime System.Span<System.StringView>.Enumerator.Current get accessor at line 376:15 in ...\corlib\src\Span.bf
  > in comptime System.Span<System.StringView>.Enumerator.GetNext() at line 415:5 in ...\corlib\src\Span.bf
  > in comptime System.String.Append(params System.Span<System.StringView> strings) at line 1056:4 in ...\corlib\src\String.bf
  > in comptime System.Reflection.TypeInstance.GetFullName(System.String strBuffer) at line 1355:11 in ...\corlib\src\Type.bf
  > in comptime System.Reflection.TypeInstance.GetFullName(System.String strBuffer) at line 1347:8 in ...\corlib\src\Type.bf
  > in comptime System.Reflection.PointerType.GetFullName(System.String strBuffer) at line 1462:4 in ...\corlib\src\Type.bf
  > in comptime System.Type.ToString(System.String strBuffer) at line 993:4 in ...\corlib\src\Type.bf
  > in comptime System.String.AppendF(System.IFormatProvider provider, System.StringView format, params System.Span<System.Object> args) at line 1533:7 in ...\corlib\src\String.bf
  > in comptime System.String.AppendF(System.StringView format, params System.Span<System.Object> args) at line 1564:4 in ...\corlib\src\String.bf
  > in comptime System.StaticHookAttribute.OnTypeInit(System.Type type, System.StaticHookAttribute* prev) at line 69:46 in ...\corlib\src\StaticHookAttribute.bf

Ready-for-testing project: bug.1960.zip
One possible solution (if I may) is to introduce an attribute that disallows new instance fields via extensions.
Last thing: I have an old build from source (14a3dd8) where crash does not occur and extending Span<T> seems to work fine.