Assert in aot compiler: mono/mini/calls.c:337, condition `!rgctx_arg || !imt_arg' not met

[rolfbjarne]

The AOT compiler crashes with:

• Assertion at /Users/builder/jenkins/workspace/archive-mono/2020-02/ios/release/mono/mini/calls.c:337, condition `!rgctx_arg || !imt_arg' not met

with this test case (unzip & execute repro.sh):

repro-7e947a4.zip

Note: needs Xamarin.iOS 16.4.0.23 - will probaby repro on earlier versions of Xamarin.iOS as well, but the script would need to be updated.

Running the AOT compiler with a bunch of -v's, reveals:

converting gsharedvt method bool Jakar.Extensions.LockerEnumerator`3<TValue_GSHAREDVT, TCloser_GSHAREDVT, TList_GSHAREDVT>:MoveNext ()
created temp 0 (R32) of type System.Byte
creating vars
created temp 1 (R33) of type System.IntPtr
	return :  arg R32 <-
	this:  arg R33 <-
creating locals
	local [0]: created temp 2 (R34) of type System.Byte
	local [1]: created temp 3 (R35) of type System.Byte
	local [2]: created temp 4 (R36) of type System.Byte
	local [3]: created temp 5 (R37) of type TList_GSHAREDVT
	local [4]: created temp 6 (R38) of type System.ReadOnlySpan<TValue_GSHAREDVT>
	local [5]: created temp 7 (R39) of type System.Byte
	local [6]: created temp 8 (R40) of type System.Byte
locals done
created temp 9 (R41) of type System.IntPtr
created temp 10 (R42) of type System.IntPtr
created temp 11 (R43) of type System.IntPtr
method to IR Jakar.Extensions.LockerEnumerator`3<TValue_GSHAREDVT, TCloser_GSHAREDVT, TList_GSHAREDVT>:MoveNext ()
created temp 12 (R44) of type System.IntPtr
created temp 13 (R45) of type System.IntPtr
created temp 14 (R49) of type System.IntPtr
converting (in B2: stack: 0) IL_0000: nop       
converting (in B2: stack: 0) IL_0001: ldarg.0   
converting (in B2: stack: 1) IL_0002: ldfld     0x0a000aa3
converting (in B2: stack: 1) IL_0007: box       0x1b00011e
created temp 15 (R54) of type TList_GSHAREDVT
converting (in B13: stack: 1) IL_000c: ldnull    
converting (in B13: stack: 2) IL_000d: ceq       
converting (in B13: stack: 1) IL_000f: stloc.1   
converting (in B13: stack: 0) IL_0010: ldloc.1   
converting (in B13: stack: 1) IL_0011: brfalse.s IL_001f
converting (in B5: stack: 0) IL_0013: nop       
converting (in B5: stack: 0) IL_0014: ldstr     "LockerEnumerator"
converting (in B5: stack: 1) IL_0019: newobj    0x0a000857
converting (in B5: stack: 1) IL_001e: throw     
converting (in B4: stack: 0) IL_001f: ldarg.0   
converting (in B4: stack: 1) IL_0020: ldflda    0x0a000aa2
converting (in B4: stack: 1) IL_0025: call      0x0a000aa4
cmethod = bool System.ReadOnlyMemory`1<TValue_GSHAREDVT>:get_IsEmpty ()
converting (in B4: stack: 1) IL_002a: stloc.2   
converting (in B4: stack: 0) IL_002b: ldloc.2   
converting (in B4: stack: 1) IL_002c: brfalse.s IL_0051
converting (in B7: stack: 0) IL_002e: nop       
converting (in B7: stack: 0) IL_002f: ldarg.0   
converting (in B7: stack: 1) IL_0030: ldc.i4.m1 
converting (in B7: stack: 2) IL_0031: stfld     0x0a000aa1
converting (in B7: stack: 0) IL_0036: ldarg.0   
converting (in B7: stack: 1) IL_0037: ldarg.0   
converting (in B7: stack: 2) IL_0038: ldfld     0x0a000aa3
converting (in B7: stack: 2) IL_003d: stloc.3   
converting (in B7: stack: 1) IL_003e: ldloca.s  3
converting (in B7: stack: 2) IL_0040: constrained.0x1b00011e
converting (in B7: stack: 2) IL_0046: callvirt  0x0a000aa5
cmethod = System.ReadOnlyMemory`1<TValue_GSHAREDVT> Jakar.Extensions.ILockedCollection`2<TCloser_GSHAREDVT, TValue_GSHAREDVT>:Copy ()
Constrained call to TList_GSHAREDVT
created temp 16 (R123) of type System.ReadOnlyMemory<TValue_GSHAREDVT>
created temp 17 (R126) of type System.ReadOnlyMemory<TValue_GSHAREDVT>
converting (in B21: stack: 2) IL_004b: stfld     0x0a000aa2
converting (in B21: stack: 0) IL_0050: nop       
converting (in B6: stack: 0) IL_0051: ldarg.0   
converting (in B6: stack: 1) IL_0052: ldflda    0x0a000aa1
converting (in B6: stack: 1) IL_0057: ldarg.0   
converting (in B6: stack: 2) IL_0058: ldflda    0x0a000aa2
converting (in B6: stack: 2) IL_005d: call      0x0a000913
cmethod = System.ReadOnlySpan`1<TValue_GSHAREDVT> System.ReadOnlyMemory`1<TValue_GSHAREDVT>:get_Span ()
created temp 18 (R147) of type System.ReadOnlySpan<TValue_GSHAREDVT>
converting (in B6: stack: 2) IL_0062: stloc.s   4
converting (in B6: stack: 1) IL_0064: ldloca.s  4
converting (in B6: stack: 2) IL_0066: ldarg.0   
converting (in B6: stack: 3) IL_0067: ldflda    0x0a000a9f
converting (in B6: stack: 3) IL_006c: call      0x0a000aa6
cmethod = bool Jakar.Extensions.ILockedCollection`2<TCloser_GSHAREDVT, TValue_GSHAREDVT>:MoveNext (int&,System.ReadOnlySpan`1<TValue_GSHAREDVT>&,TValue_GSHAREDVT&)
* Assertion at /Users/builder/jenkins/workspace/archive-mono/2020-02/ios/release/mono/mini/calls.c:337, condition `!rgctx_arg || !imt_arg' not met

which seems to be this method: https://github.com/Jakar510/Jakar.Extensions/blob/5e60cc3cec27e13eae54ca49aa80d7a8c0e4741c/Jakar.Extensions/Models/LockerEnumerator.cs#L27-L42