AstGen: missing compile error for return inside defer expression

[andrewrk]

extern fn bar() void;

export fn foo() void {
    defer bar();
    defer return;
}

stage1 gives the correct result:

./test.zig:5:11: error: cannot return from defer expression
    defer return;
          ^

stage2 does not catch the problem. It should be caught in AstGen:

[nix-shell:~/dev/zig/build-release]$ ./zig-out/bin/zig astgen test.zig
# Source bytes:       83B
# Tokens:             24 (144B)
# AST Nodes:          12 (276B)
# Total ZIR bytes:    414B
# Instructions:       16 (144B)
# String Table Bytes: 10B
# Extra Data Items:   49 (196B)
%15 = extended(struct_decl(parent, Auto, {
  [35] bar line(0) hash(a136708cffc080900b4d0ec55ba4898f): %0 = block_inline({
    %1 = extended(func([], @Ref.void_type, cc=@Ref.calling_convention_c, extern, {}) node_offset:1:8
    %2 = break_inline(%0, %1)
  }) node_offset:1:8
  [42] export foo line(2) hash(29d6f5fbb9c6edc9aaf52cebc6e0ab46): %3 = block_inline({
    %13 = func([], @Ref.void_type, {
      %4 = dbg_stmt(2, 10)
      %5 = dbg_stmt(1, 10)
      %6 = decl_val("bar") token_offset:4:11
      %7 = call_chkused(%6, []) node_offset:4:14
      %8 = ret_node(@Ref.void_value) node_offset:5:11
      %9 = dbg_stmt(1, 10)
      %10 = decl_val("bar") token_offset:4:11
      %11 = call_chkused(%10, []) node_offset:4:14
      %12 = ret_coerce(@Ref.void_value) token_offset:6:1
    }) (lbrace=0:21,rbrace=3:0) node_offset:3:8
    %14 = break_inline(%3, %13)
  }) node_offset:3:8
}, {}, {})