invalid llvm code gen on missing try/catch on assignment to struct member

[slaide]

const std = @import("std");

const A=struct{
  memb: []i32,
};
const B=struct{
  memb: i32,
};

fn myAlloc(arg: bool) !i32{
  if(arg){
    return error.TestFailure;
  }else{
    return 2;
  }
}

pub fn main() anyerror!void {
  
  
  //#1
  
  var hi: []i32=std.heap.direct_allocator.alloc(i32,2);
  
  
  //#2
  
  //var res: A=undefined;
  //res.memb=std.heap.direct_allocator.alloc(i32,2);
  
  
  //#3
  
  //var perr: anyerror!i32=error.Failed;
  //var perr: error{OutOfMemory}!i32=error.OutOfMemory;
  //var btest:B=undefined;
  //btest.memb=perr;
  
  
  //#4
  
  //var res: B=undefined;
  //res.memb=myAlloc(true);
}

case 1 is how the code should behave, which is correct. it produces an error that the types are invalid.

case 2 is the minimal working example for this error. this should fail to compile, but it does not. instead this is shown:

Call parameter type does not match function signature!
  %12 = getelementptr inbounds %A, %A* %res, i32 0, i32 0, !dbg !14122
 { %"[]i32", i16 }*  call fastcc void @std.mem.Allocator.alloc.154(%"[]i32"* sret %12, %builtin.StackTrace* %0, %std.mem.Allocator* @direct_allocator_state, i64 2), !dbg !14123
LLVM ERROR: Broken module found, compilation aborted!

case 3 also behaves correctly though. does not compile, because of differing types. (both error-type-unions behave the same way. i dont know if this may be specific to the errors-unions specified by the alloc function)

case 4 also behaves the way it should. does not compile due to type incompatibility.

zig version: 0.4.0+cf4bccf7 (from snap package) on linux x86_64.