The main problem was that the loop body was treated as an expression
that was one of the peer result values of a loop, when in reality the
loop body is noreturn and only the `break` operands are the result
values of loops.
This was solved by introducing an override that prevents rvalue() from
emitting a store to result location instruction for loop bodies.
An orthogonal change also included in this commit is switching
`elem_val` index expressions to using `coerced_ty` and doing the
coercion to `usize` inside `Sema`, resulting in smaller ZIR (since the
cast becomes implied).
I also changed the break operand expression to use `reachableExpr`,
introducing a new compile error for double break.
This makes a few more behavior tests pass for `while` and `for` loops.
* stage1: change the `@typeName` of `@TypeOf(undefined)`,
`@TypeOf(null)`, and `@TypeOf(.foo)` to match stage2.
* move passing behavior tests to the passing-for-stage2 section.
Conflicts:
* doc/langref.html.in
* lib/std/enums.zig
* lib/std/fmt.zig
* lib/std/hash/auto_hash.zig
* lib/std/math.zig
* lib/std/mem.zig
* lib/std/meta.zig
* test/behavior/alignof.zig
* test/behavior/bitcast.zig
* test/behavior/bugs/1421.zig
* test/behavior/cast.zig
* test/behavior/ptrcast.zig
* test/behavior/type_info.zig
* test/behavior/vector.zig
Master branch added `try` to a bunch of testing function calls, and some
lines also had changed how to refer to the native architecture and other
`@import("builtin")` stuff.
