Switch expression returns incorrect value.

[neuring]

Hello, I encountered the following bug when trying to use switch expressions.

When running the code below, I would expect that the variable state to change to the value States.B after char changes to the value '.'.
Instead the value of state stays the same.

When examining the assembly it seems that the value is correctly changed at first, but shortly after replaced with the value of States.A
https://godbolt.org/z/d9aaTj6z8

const std = @import("std");

pub fn parse_number(input: []const u8) void {
    const States = enum { A, B};

    var current: usize = 0;

    var state = States.A;
    
    while (true) {
        const char = if (current < input.len)
            input[current]
        else
            break;

        std.debug.print("char = {c}, state before = {a}\n", .{ char, state });
        state = switch (state) {
            States.A => switch (char) {
                '0'...'9' => blk1: {
                    std.debug.print("AAAAAA\n", .{});
                    break :blk1 States.A;
                },
                '.' => blk2: {
                    std.debug.print("BBBBBB\n", .{});
                    break :blk2 States.B;
                },
                else => break,
            },
            States.B => break,
        };
        std.debug.print("state after = {a}\n", .{state});

        current += 1;
    }
}

pub fn main() void {
    parse_number("14.55");
}

Output

char = 1, state before = States.A
AAAAAA
state after = States.A
char = 4, state before = States.A
AAAAAA
state after = States.A
char = ., state before = States.A
BBBBBB
state after = States.A
char = 5, state before = States.A
AAAAAA
state after = States.A
char = 5, state before = States.A
AAAAAA
state after = States.A

I'm using zig version 0.8.0-dev.2008+6cd71931c.

[Sirius902]

I'm also having a similar problem where the result of a switch is different if the variable is const. Example:

const std = @import("std");

pub fn main() void {
    const x: u32 = 1;
    var y = x;

    std.log.info("{s}", .{switch (x) {
        0 => @as([]const u8, "a"),
        1 => @as([]const u8, "b"),
        2 => @as([]const u8, "c"),
        else => @as([]const u8, "wow"),
    }});

    std.log.info("{s}", .{switch (y) {
        0 => @as([]const u8, "a"),
        1 => @as([]const u8, "b"),
        2 => @as([]const u8, "c"),
        else => @as([]const u8, "wow"),
    }});
}

The above program prints

info: b
info: wow

instead of the expected

info: b
info: b

[ryoppippi]

const std = @import("std");

pub fn main() void {
    var y: u32 = 1;
    var answer = switch (y) {
        1 => @as([]const u8, "b"),
        else => @as([]const u8, "wow"),
    };

    std.log.info("{d},{s}", .{ y, answer });
}

This works. So I think this may not be a problem of switch expression?

[ryoppippi]

const std = @import("std");

pub fn main() void {
    var y: u32 = 1;

    std.log.info("{s}", .{switch (y) {
        1 => @as([]const u8, "b"),
        else => unreachable,
    }});
}

Also this works.

[nektro]

@Sirius902's case is a duplicate of #7097

[ryoppippi]

idk I tested this behavior on the nightly build. so if this problem still exists, you can keep this issue.

[nektro]

unless the initial code snippet is also a duplicate, it needs to be added to https://github.com/ziglang/zig/tree/master/test/cases/ to catch/prevent regressions in order for the issue to be closed

[ryoppippi]

ok so
@Sirius902's problem and @neuring's problem are different ones. I understand what you mean @nektro
Thanks