Result type lost when nesting multiple expressions

[SpexGuy]

This was found by @devzero. I'm not sure if this is a bug report or a proposal, but it seems pretty clear to me that this should compile:

const Enum = enum { a, b };

pub fn main() !void {
    var x: usize = 4;
    var y = false;
    var e: Enum = switch(x) {
        else => blk: {
            if (y) {
                break :blk .a;
            }
            break :blk .b;
        }
    };
}

Instead it reports this error:

.\src\day08.zig:7:22: error: values of type '(enum literal)' must be comptime known
        else => blk: {
                     ^
C:\Program Files\Zig\Current\lib\zig\std\start.zig:334:40: note: referenced here
            const result = root.main() catch |err| {
                                       ^

---

It seems like the problem is that the named block in the switch is not inferring the result type from the switch expression. So when the compiler tries to compile the break statements, it does peer type resolution instead of result type inference and comes up with EnumLiteral. Since EnumLiterals can't be runtime values, compilation fails.

The specific behavior I think should work is:

• result types should be inferred through if, else, and switch expressions into their sub-expressions.
• result types should be inferred through while, for, and block expressions into their associated break statements.

[ghost]

I think this is #5557

[Vexu]

Duplicate of #5557, #3750, #4255 and. #4629, already fixed in stage2.