Type casting *T to *[1]T and then []const T gives bogus compile error in some contexts

[thejoshwolfe]

I added some whitespace to make the problem more obvious:

const assert = @import("std").debug.assert;
test "asdf" {
    var x: i32 = 1234;
    assert(    @as([]const i32, @as(*[1]i32, &x))[0] == 1234);
    const z1 = @as([]const i32, @as(*[1]i32, &x)); // COMPILE ERROR HERE
    assert(z1[0] == 1234);
}

./test.zig:3:5: error: expected type '[]const i32', found '*i32'
    var x: i32 = 1234;
    ^
./test.zig:5:47: note: referenced here
    const z1 = @as([]const i32, @as(*[1]i32, &x)); // COMPILE ERROR HERE
                                              ^

There are other manifestations of this problem, such as this:

const assert = @import("std").debug.assert;
test "asdf" {
    var x: i32 = 1234;
    assert(foo(&x)[0] == 1234);
    assert(bar(&x)[0] == 1234);
}
fn foo(x: *i32) []const i32 {
    const ret = @as(*[1]i32, x);
    return ret;
}
fn bar(x: *i32) []const i32 {
    return @as(*[1]i32, x); // COMPILE ERROR HERE
}

./test.zig:12:25: error: expected type '[]const i32', found '*i32'
    return @as(*[1]i32, x); // COMPILE ERROR HERE
                        ^

using zig-linux-x86_64-0.6.0+a7a8c433d.