Compiler crash with invalid object variant

[Clyybber]

The following snippets should provide a better error, saying that object variants/case objects are only supported with enums as discriminators.

Example

type Cobj = object
  case a: int
  of 7:
    b: bool
    bb: bool
  of 1:
    i: int
    u: uint
  else:
    uuu: uint8

var t = Cobj(a: 3)
t.i = 1

Current Output

/home/clyybber/builds/nim/compiler/nim.nim(106) nim
/home/clyybber/builds/nim/compiler/nim.nim(83) handleCmdLine
/home/clyybber/builds/nim/compiler/cmdlinehelper.nim(98) loadConfigsAndRunMainCommand
/home/clyybber/builds/nim/compiler/main.nim(188) mainCommand
/home/clyybber/builds/nim/compiler/main.nim(92) commandCompileToC
/home/clyybber/builds/nim/compiler/modules.nim(144) compileProject
/home/clyybber/builds/nim/compiler/modules.nim(85) compileModule
/home/clyybber/builds/nim/compiler/passes.nim(210) processModule
/home/clyybber/builds/nim/compiler/passes.nim(86) processTopLevelStmt
/home/clyybber/builds/nim/compiler/cgen.nim(1857) myProcess
/home/clyybber/builds/nim/compiler/ccgstmts.nim(1263) genStmts
/home/clyybber/builds/nim/compiler/ccgexprs.nim(2621) expr
/home/clyybber/builds/nim/compiler/ccgexprs.nim(2406) genStmtList
/home/clyybber/builds/nim/compiler/ccgstmts.nim(1263) genStmts
/home/clyybber/builds/nim/compiler/ccgexprs.nim(2651) expr
/home/clyybber/builds/nim/compiler/ccgstmts.nim(1247) genAsgn
/home/clyybber/builds/nim/compiler/ccgexprs.nim(2618) expr
/home/clyybber/builds/nim/compiler/ccgexprs.nim(837) genCheckedRecordField
/home/clyybber/builds/nim/compiler/ccgexprs.nim(809) genFieldCheck
/home/clyybber/builds/nim/compiler/cgen.nim(575) initLocExpr
/home/clyybber/builds/nim/compiler/ccgexprs.nim(2594) expr
/home/clyybber/builds/nim/compiler/ccgexprs.nim(126) genSetNode
/home/clyybber/builds/nim/compiler/types.nim(1394) getSize
/home/clyybber/builds/nim/compiler/sizealignoffsetimpl.nim(292) computeSizeAlign
/home/clyybber/builds/nim/compiler/int128.nim(72) toInt64
/home/clyybber/builds/nim/lib/system/assertions.nim(27) failedAssertImpl
/home/clyybber/builds/nim/lib/system/assertions.nim(20) raiseAssert
/home/clyybber/builds/nim/lib/system/fatal.nim(39) sysFatal
Error: unhandled exception: /home/clyybber/builds/nim/compiler/int128.nim(72, 11) `arg.sdata(2) == 0` out of range [AssertionError]

Changing the discriminators type to int32 traps the compiler in an infinite loop.

Additional Information

$ nim -v
Nim Compiler Version 1.0.99

[dawkot]

object variants/case objects are only supported with enums as discriminators

They are also supported with bool and ints/uints below size of 32

[Clyybber]

Doesn't seem to be fixed.

[mratsim]

Please also allow booleans as discriminator (didn't check lately but it used to work)

[Clyybber]

This snippet is supposed to work afaict, since the error messages in semobjconstr and the tests for discriminators seem to indicate that:
discriminators with integers with size > 16 bits should only work when the discriminator value passed to the object constructor is a const. This does not actually work though. (Replace the last line in my snippet with a valid assign)
Also when its supposed to work like that its also supposed to work for runtime discriminator values that have a type (range) that is specific enough so that the appropriate branch can be determined at compile time.

EDIT: OTOH the error here seems to stem from the fact that the backend still generates those checks and those checks rely on the size being <= 16 bits.. afaict
cc @Araq on wether size > 16 bits is supposed to work in some cases or not at all.

[Clyybber]

As this crashes:

type
 E = enum
  a = 1
  b = high(int32)
 Cobj = object
  case a: E
  of a:
    b: bool
    bb: bool
  of b:
    i: int
    u: uint

var t = Cobj(a: E.a)
t.b = true
echo t

and this:

type
 E = enum
  c = 0
  a = 1
  b = high(int32)
 Cobj = object
  case a: E
  of a:
    b: bool
    bb: bool
  of b:
    i: int
    u: uint
  else:
    uuu: uint8

var t = Cobj(a: E.a)
t.b = true
echo t

both hang up gcc(??). I think size > 16bits is just not supported.
I'll include proper errors for this in my PR. (If I am right)