WebAssembly has several operators that imply that any code following them until the next end or else operator will never be executed: ret, br, br_table, unreachable.

I propose that these operators act as implicit end/else operators. This would imply that they may only occur at the end of a control flow block. The end operator would still be useful as a special-case br operator that targets a fixed depth of 0.

This also makes it clear that else can be eliminated, and that an if operator just needs to be followed by two terminator instructions.

I believe this simplifies code generation, since you don't need to worry about the stack having the right type going into an unreachable end operator. I believe it also simplifies the spec and validation, since it completely avoids the question of how to handle code between these operators and the next end.