behavior: add test coverage for slicing zero length array field of struct

Closes ziglang#11787

Author: wooster0

lib/std/segmented_list.zig

@@ -412,10 +412,7 @@ pub fn SegmentedList(comptime T: type, comptime prealloc_item_count: usize) type
 }
 
 test "SegmentedList basic usage" {
-    if (false) {
-        // https://github.com/ziglang/zig/issues/11787
-        try testSegmentedList(0);
-    }
+    try testSegmentedList(0);
     try testSegmentedList(1);
     try testSegmentedList(2);
     try testSegmentedList(4);

test/behavior.zig

@@ -81,6 +81,7 @@ test {
     _ = @import("behavior/bugs/11179.zig");
     _ = @import("behavior/bugs/11181.zig");
     _ = @import("behavior/bugs/11213.zig");
+    _ = @import("behavior/bugs/11787.zig");
     _ = @import("behavior/bugs/11816.zig");
     _ = @import("behavior/bugs/12003.zig");
     _ = @import("behavior/bugs/12025.zig");

test/behavior/bugs/11787.zig

@@ -0,0 +1,13 @@
+const std = @import("std");
+const testing = std.testing;
+
+test "slicing zero length array field of struct" {
+    const S = struct {
+        a: [0]usize,
+        fn foo(self: *@This(), start: usize, end: usize) []usize {
+            return self.a[start..end];
+        }
+    };
+    var s: S = undefined;
+    try testing.expect(s.foo(0, 0).len == 0);
+}