stage2: integer-backed packed structs

This implements #10113 for the self-hosted compiler only. It removes the
ability to override alignment of packed struct fields, and removes the
ability to put pointers and arrays inside packed structs.

After this commit, nearly all the behavior tests pass for the stage2 llvm
backend that involve packed structs.

I didn't implement the compile errors or compile error tests yet. I'm
waiting until we have stage2 building itself and then I want to rework
the compile error test harness with inspiration from Vexu's arocc test
harness. At that point it should be a much nicer dev experience to work
on compile errors.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/AstGen.zig b/src/AstGen.zig
index 1b2f598ace..8e2362ade1 100644
--- a/src/AstGen.zig
+++ b/src/AstGen.zig
@@ -4002,6 +4002,9 @@ fn structDeclInner(
         wip_members.nextField(bits_per_field, .{ have_align, have_value, is_comptime, unused });
 
         if (have_align) {
+            if (layout == .Packed) {
+                try astgen.appendErrorNode(member.ast.align_expr, "unable to override alignment of packed struct fields", .{});
+            }
             const align_inst = try expr(&block_scope, &namespace.base, align_rl, member.ast.align_expr);
             wip_members.appendToField(@enumToInt(align_inst));
         }