Permit expression parameter for comma-list switch case for simple values

[chr-1x]

const std = @import("std");

pub fn main() void {
 var d: u8 = 'd';
 switch (d) {
 'a'...'c' => |c| std.debug.print("abc ({c})\n", .{c}),
 'd', 'e' => |c| std.debug.print("de ({c})\n", .{c}),
 else => |c| std.debug.print("other ({c})\n", .{c}),
 }
}

./repro_switch_capture.zig:7:22: error: switch on type 'u8' provides no expression parameter
 'd', 'e' => |c| std.debug.print("de ({c})\n", c),

» zig version
0.7.0+39336fd2e

I believe that an expression parameter would be useful here as, just like in the range-of-values situation, it makes the task of figuring out which case was matched more succinct.

Zig 0.7.0 documentation demonstrates using this for a union(enum) type, so it's surprising that it doesn't work in the simpler case of a plain value:

 // Switching on more complex enums is allowed.
 const b = switch (a) {
 // A capture group is allowed on a match, and will return the enum
 // value matched. If the payload types of both cases are the same
 // they can be put into the same switch prong.
 Item.a, Item.e => |item| item,

 // A reference to the matched value can be obtained using `*` syntax.
 Item.c => |*item| blk: {
 item.*.x += 1;
 break :blk 6;
 },

 // No else is required if the types cases was exhaustively handled
 Item.d => 8,
 };

Additionally, the error can currently be bypassed by converting one of the comma-separated cases to a trivial range:

const std = @import("std");

pub fn main() void {
 var d: u8 = 'd';
 switch (d) {
 'a'...'c' => |c| std.debug.print("abc ({c})\n", .{c}),
 'd'...'d', 'e' => |c| std.debug.print("de ({c})\n", .{c}),
 else => |c| std.debug.print("other ({c})\n", .{c}),
 }
}