Sema: Fix many-pointer array concatenation at comptime (#11512)

* Sema: Correctly determine whether array_cat lhs and rhs are single ptrs

Many-pointers are also not single-pointers and wouldn't be considered
here. This commit makes the conditions use the appropriately-named
isSinglePointer instead.

* Sema: Correctly obtain ArrayInfo for many-pointer concatenation

Many-pointers at comptime have a known size like slices and can be used
in array concatenation. This fixes a stage1 regression.

* test: Add comptime manyptr concatenation test

Co-authored-by: sin-ack <sin-ack@users.noreply.github.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/test/behavior/basic.zig b/test/behavior/basic.zig
index d608cba98b..12ead179f4 100644
--- a/test/behavior/basic.zig
+++ b/test/behavior/basic.zig
@@ -709,6 +709,31 @@ test "string concatenation" {
     try expect(b[len] == 0);
 }
 
+fn manyptrConcat(comptime s: [*:0]const u8) [*:0]const u8 {
+    return "very " ++ s;
+}
+
+test "comptime manyptr concatenation" {
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
+
+    const s = "epic";
+    const actual = manyptrConcat(s);
+    const expected = "very epic";
+
+    const len = mem.len(actual);
+    const len_with_null = len + 1;
+    {
+        var i: u32 = 0;
+        while (i < len_with_null) : (i += 1) {
+            try expect(actual[i] == expected[i]);
+        }
+    }
+    try expect(actual[len] == 0);
+    try expect(expected[len] == 0);
+}
+
 test "thread local variable" {
     if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO