diff --git a/resources/lib/std/runtime.c3 b/resources/lib/std/runtime.c3
index d8a053108..81ed609d4 100644
--- a/resources/lib/std/runtime.c3
+++ b/resources/lib/std/runtime.c3
@@ -26,7 +26,3 @@ struct VarArrayHeader
 
 }
 
-struct VarArrayContainer
-{
-
-}
diff --git a/src/compiler/codegen_general.c b/src/compiler/codegen_general.c
index f1ee04af1..ee65e536f 100644
--- a/src/compiler/codegen_general.c
+++ b/src/compiler/codegen_general.c
@@ -268,6 +268,8 @@ bool type_is_homogenous_aggregate(Type *type, Type **base, unsigned *elements)
 				if (type_size(*base) * *elements != type_size(type)) return false;
 			}
 			goto TYPECHECK;
+		case TYPE_FLEXIBLE_ARRAY:
+			return false;
 		case TYPE_ARRAY:
 			// Empty arrays? Not homogenous.
 			if (type->array.len == 0) return false;
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index 857dec0a7..eb29e6fde 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -100,7 +100,7 @@ typedef enum
 	CONST_INIT_ARRAY,
 	CONST_INIT_ARRAY_FULL,
 	CONST_INIT_ARRAY_VALUE,
-	} ConstInitType;
+} ConstInitType;
 
 
 typedef struct ConstInitializer_
@@ -2054,6 +2054,7 @@ Type *type_get_ptr(Type *ptr_type);
 Type *type_get_ptr_recurse(Type *ptr_type);
 Type *type_get_subarray(Type *arr_type);
 Type *type_get_inferred_array(Type *arr_type);
+Type *type_get_flexible_array(Type *arr_type);
 Type *type_get_failable(Type *failable_type);
 Type *type_get_vector(Type *vector_type, unsigned len);
 Type *type_get_vector_bool(Type *original_type);
diff --git a/src/compiler/enums.h b/src/compiler/enums.h
index 86b80056f..a1fccfb11 100644
--- a/src/compiler/enums.h
+++ b/src/compiler/enums.h
@@ -554,6 +554,7 @@ typedef enum
 	TYPE_ARRAY,
 	TYPE_SUBARRAY,
 	TYPE_INFERRED_ARRAY,
+	TYPE_FLEXIBLE_ARRAY,
 	TYPE_UNTYPED_LIST,
 	TYPE_FAILABLE,
 	TYPE_FAILABLE_ANY,
diff --git a/src/compiler/headers.c b/src/compiler/headers.c
index fe192ec16..3c5b8281e 100644
--- a/src/compiler/headers.c
+++ b/src/compiler/headers.c
@@ -97,6 +97,8 @@ static void header_print_type(FILE *file, Type *type)
 		case TYPE_ERRTYPE:
 			OUTPUT("enum %s__", type->decl->external_name);
 			return;
+		case TYPE_FLEXIBLE_ARRAY:
+			TODO
 		case TYPE_FUNC:
 			TODO
 		case TYPE_STRUCT:
diff --git a/src/compiler/llvm_codegen.c b/src/compiler/llvm_codegen.c
index 30c284a1e..00c69e918 100644
--- a/src/compiler/llvm_codegen.c
+++ b/src/compiler/llvm_codegen.c
@@ -328,6 +328,7 @@ void llvm_emit_ptr_from_array(GenContext *c, BEValue *value)
 			return;
 		case TYPE_ARRAY:
 		case TYPE_VECTOR:
+		case TYPE_FLEXIBLE_ARRAY:
 			return;
 		case TYPE_SUBARRAY:
 		{
diff --git a/src/compiler/llvm_codegen_c_abi_x64.c b/src/compiler/llvm_codegen_c_abi_x64.c
index c5066133e..3e4697daf 100644
--- a/src/compiler/llvm_codegen_c_abi_x64.c
+++ b/src/compiler/llvm_codegen_c_abi_x64.c
@@ -442,6 +442,7 @@ static void x64_classify(Type *type, ByteSize offset_base, X64Class *lo_class, X
 		case TYPE_UNION:
 			x64_classify_struct_union(type, offset_base, current, lo_class, hi_class, named);
 			break;
+		case TYPE_FLEXIBLE_ARRAY:
 		case TYPE_ARRAY:
 			x64_classify_array(type, offset_base, current, lo_class, hi_class, named);
 			break;
@@ -574,6 +575,8 @@ AbiType *x64_get_int_type_at_offset(Type *type, unsigned offset, Type *source_ty
 			if (offset < 8) return abi_type_new_plain(type_voidptr);
 			if (offset < 16) return abi_type_new_plain(type_ulong);
 			break;
+		case TYPE_FLEXIBLE_ARRAY:
+			UNREACHABLE
 		case TYPE_ARRAY:
 		{
 			Type *element = type->array.base;
diff --git a/src/compiler/llvm_codegen_c_abi_x86.c b/src/compiler/llvm_codegen_c_abi_x86.c
index b1f14a0ea..d335a0618 100644
--- a/src/compiler/llvm_codegen_c_abi_x86.c
+++ b/src/compiler/llvm_codegen_c_abi_x86.c
@@ -120,6 +120,7 @@ static bool x86_should_return_type_in_reg(Type *type)
 		case CT_TYPES:
 		case TYPE_FAILABLE:
 		case TYPE_FAILABLE_ANY:
+		case TYPE_FLEXIBLE_ARRAY:
 			UNREACHABLE
 		case ALL_INTS:
 		case ALL_FLOATS:
@@ -597,6 +598,7 @@ static ABIArgInfo *x86_classify_argument(CallABI call, Regs *regs, Type *type)
 		case TYPE_FAILABLE:
 		case TYPE_FAILABLE_ANY:
 		case CT_TYPES:
+		case TYPE_FLEXIBLE_ARRAY:
 			UNREACHABLE
 		case ALL_FLOATS:
 		case ALL_INTS:
diff --git a/src/compiler/llvm_codegen_debug_info.c b/src/compiler/llvm_codegen_debug_info.c
index 62649c1a5..4f404a77a 100644
--- a/src/compiler/llvm_codegen_debug_info.c
+++ b/src/compiler/llvm_codegen_debug_info.c
@@ -543,6 +543,7 @@ static inline LLVMMetadataRef llvm_get_debug_type_internal(GenContext *c, Type *
 		case TYPE_TYPEDEF:
 			return type->backend_debug_type = llvm_debug_typedef_type(c, type);
 		case TYPE_ARRAY:
+		case TYPE_FLEXIBLE_ARRAY:
 			return type->backend_debug_type = llvm_debug_array_type(c, type);
 		case TYPE_SUBARRAY:
 			return type->backend_debug_type = llvm_debug_subarray_type(c, type);
diff --git a/src/compiler/llvm_codegen_expr.c b/src/compiler/llvm_codegen_expr.c
index d4ed6a435..ce287079c 100644
--- a/src/compiler/llvm_codegen_expr.c
+++ b/src/compiler/llvm_codegen_expr.c
@@ -491,6 +491,13 @@ static inline void llvm_emit_subscript_addr_with_base(GenContext *c, BEValue *re
 		case TYPE_POINTER:
 			llvm_value_set_address(result, llvm_emit_pointer_inbounds_gep_raw(c, llvm_get_pointee_type(c, parent->type), parent->value, index->value), type->pointer);
 			return;
+		case TYPE_FLEXIBLE_ARRAY:
+		{
+			AlignSize alignment;
+			LLVMValueRef ptr = llvm_emit_array_gep_raw_index(c, parent->value, llvm_get_type(c, type), index->value, parent->alignment, &alignment);
+			llvm_value_set_address_align(result, ptr, type->array.base, alignment);
+			return;
+		}
 		case TYPE_ARRAY:
 		case TYPE_VECTOR:
 			// TODO vector
@@ -3861,6 +3868,7 @@ static void llvm_expand_type_to_args(GenContext *context, Type *param_type, LLVM
 		case TYPE_FAILABLE:
 		case CT_TYPES:
 		case TYPE_FAILABLE_ANY:
+		case TYPE_FLEXIBLE_ARRAY:
 			UNREACHABLE
 			break;
 		case TYPE_BOOL:
diff --git a/src/compiler/llvm_codegen_type.c b/src/compiler/llvm_codegen_type.c
index 327935c38..52627cf51 100644
--- a/src/compiler/llvm_codegen_type.c
+++ b/src/compiler/llvm_codegen_type.c
@@ -352,6 +352,7 @@ LLVMTypeRef llvm_get_type(GenContext *c, Type *any_type)
 		case TYPE_POINTER:
 			return any_type->backend_type = llvm_type_from_ptr(c, any_type);
 		case TYPE_ARRAY:
+		case TYPE_FLEXIBLE_ARRAY:
 			return any_type->backend_type = llvm_type_from_array(c, any_type);
 		case TYPE_SUBARRAY:
 		{
diff --git a/src/compiler/sema_casts.c b/src/compiler/sema_casts.c
index 8814b274e..dbb9cb925 100644
--- a/src/compiler/sema_casts.c
+++ b/src/compiler/sema_casts.c
@@ -389,6 +389,7 @@ CastKind cast_to_bool_kind(Type *type)
 		case TYPE_FAILABLE:
 		case TYPE_ANY:
 		case TYPE_FAILABLE_ANY:
+		case TYPE_FLEXIBLE_ARRAY:
 			return CAST_ERROR;
 	}
 	UNREACHABLE
@@ -481,6 +482,8 @@ bool cast_may_explicit(Type *from_type, Type *to_type, bool ignore_failability,
 		case TYPE_ERRTYPE:
 			// Allow MyError.A -> error, to an integer or to bool
 			return to_type->type_kind == TYPE_ANYERR || type_is_integer(to_type) || to_type == type_bool;
+		case TYPE_FLEXIBLE_ARRAY:
+			return false;
 		case TYPE_ARRAY:
 			if (to_kind == TYPE_VECTOR)
 			{
@@ -1260,6 +1263,8 @@ static bool cast_inner(Expr *expr, Type *from_type, Type *to, Type *to_type)
 			if (to == type_bool) return err_to_bool(expr, to_type);
 			if (type_is_integer(to)) return insert_cast(expr, CAST_ERINT, to_type);
 			break;
+		case TYPE_FLEXIBLE_ARRAY:
+			return false;
 		case TYPE_ARRAY:
 			if (to->type_kind == TYPE_VECTOR) return insert_cast(expr, CAST_ARRVEC, to_type);
 			FALLTHROUGH;
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index 205937398..f1538e997 100644
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -83,19 +83,30 @@ static inline bool sema_analyse_struct_member(Context *context, Decl *decl)
 		}
 		if (decl->name) sema_add_member(context, decl);
 	}
+
 	switch (decl->decl_kind)
 	{
 		case DECL_VAR:
 			assert(decl->var.kind == VARDECL_MEMBER);
 			decl->resolve_status = RESOLVE_RUNNING;
-			if (!sema_resolve_type_info(context, decl->var.type_info)) return decl_poison(decl);
+			if (!sema_resolve_type_info_maybe_inferred(context, decl->var.type_info, true)) return decl_poison(decl);
 			decl->type = decl->var.type_info->type;
 			decl->resolve_status = RESOLVE_DONE;
+			Type *member_type = type_flatten_distinct(decl->type);
+			if (member_type->type_kind == TYPE_ARRAY)
+			{
+				if (member_type->array.len == 0)
+				{
+					SEMA_ERROR(decl, "Zero length arrays are not valid members.");
+					return false;
+				}
+			}
 			return true;
 		case DECL_STRUCT:
 		case DECL_UNION:
 		case DECL_BITSTRUCT:
-			return sema_analyse_decl(context, decl);
+			if (!sema_analyse_decl(context, decl)) return false;
+			return true;
 		default:
 			UNREACHABLE
 	}
@@ -107,6 +118,7 @@ static bool sema_analyse_union_members(Context *context, Decl *decl, Decl **memb
 	MemberIndex max_alignment_element = 0;
 	AlignSize max_alignment = 0;
 
+	bool has_named_parameter = false;
 	VECEACH(members, i)
 	{
 		Decl *member = members[i];
@@ -124,7 +136,11 @@ static bool sema_analyse_union_members(Context *context, Decl *decl, Decl **memb
 			}
 			continue;
 		}
-
+		if (member->type->type_kind == TYPE_INFERRED_ARRAY)
+		{
+			SEMA_ERROR(member, "Flexible array members not allowed in unions.");
+			return false;
+		}
 		AlignSize member_alignment = type_abi_alignment(member->type);
 		ByteSize member_size = type_size(member->type);
 		assert(member_size <= MAX_TYPE_SIZE);
@@ -195,13 +211,14 @@ static bool sema_analyse_union_members(Context *context, Decl *decl, Decl **memb
 
 static bool sema_analyse_struct_members(Context *context, Decl *decl, Decl **members)
 {
-	// Default alignment is 1 even if the it is empty.
+	// Default alignment is 1 even if it is empty.
 	AlignSize natural_alignment = 1;
 	bool is_unaligned = false;
 	AlignSize size = 0;
 	AlignSize offset = 0;
 	bool is_packed = decl->is_packed;
-	VECEACH(members, i)
+	unsigned member_count = vec_size(members);
+	for (unsigned i = 0; i < member_count; i++)
 	{
 		Decl *member = decl->strukt.members[i];
 		if (!decl_ok(member))
@@ -218,6 +235,31 @@ static bool sema_analyse_struct_members(Context *context, Decl *decl, Decl **mem
 			}
 			continue;
 		}
+		Type *member_type = type_flatten_distinct(member->type);
+		if (member_type->type_kind == TYPE_STRUCT && member_type->decl->has_variable_array)
+		{
+			if (i != member_count - 1)
+			{
+				SEMA_ERROR(member, "A struct member with a flexible array must be the last element.");
+				return false;
+			}
+			decl->has_variable_array = true;
+		}
+		if (member_type->type_kind == TYPE_INFERRED_ARRAY)
+		{
+			if (i != member_count - 1)
+			{
+				SEMA_ERROR(member, "The flexible array member must be the last element.");
+				return false;
+			}
+			if (i == 0)
+			{
+				SEMA_ERROR(member, "The flexible array member cannot be the only element.");
+				return false;
+			}
+			member->type = type_get_flexible_array(member->type->array.base);
+			decl->has_variable_array = true;
+		}
 
 		if (!decl_ok(decl)) return false;
 
@@ -366,6 +408,12 @@ static bool sema_analyse_struct_union(Context *context, Decl *decl)
 
 	DEBUG_LOG("Beginning analysis of %s.", decl->name ? decl->name : "anon");
 	bool success;
+	Decl **members = decl->strukt.members;
+	if (!vec_size(members))
+	{
+		SEMA_ERROR(decl, decl->decl_kind == DECL_UNION ? "Zero sized unions are not permitted." : "Zero sized structs are not permitted.");
+		return false;
+	}
 	if (decl->name)
 	{
 		SCOPE_START
@@ -663,7 +711,13 @@ static inline bool sema_analyse_typedef(Context *context, Decl *decl)
 		return true;
 	}
 	if (!sema_resolve_type_info(context, decl->typedef_decl.type_info)) return false;
-	decl->type->canonical = decl->typedef_decl.type_info->type->canonical;
+	Type *type = decl->typedef_decl.type_info->type->canonical;
+	if (type == type_anyerr || type == type_any)
+	{
+		SEMA_ERROR(decl->typedef_decl.type_info, "%s may not be aliased.", type_quoted_error_string(type));
+		return false;
+	}
+	decl->type->canonical = type;
 	// Do we need anything else?
 	return true;
 }
@@ -687,6 +741,7 @@ static inline bool sema_analyse_distinct(Context *context, Decl *decl)
 		case TYPE_TYPEDEF:
 		case TYPE_DISTINCT:
 		case CT_TYPES:
+		case TYPE_FLEXIBLE_ARRAY:
 			UNREACHABLE
 			return false;
 		case TYPE_FAILABLE_ANY:
diff --git a/src/compiler/sema_expr.c b/src/compiler/sema_expr.c
index b6d6f9398..37f0659e9 100644
--- a/src/compiler/sema_expr.c
+++ b/src/compiler/sema_expr.c
@@ -2299,6 +2299,7 @@ static bool expr_check_index_in_range(Context *context, Type *type, Expr *index_
 	switch (type->type_kind)
 	{
 		case TYPE_POINTER:
+		case TYPE_FLEXIBLE_ARRAY:
 			assert(!from_end);
 			return true;
 		case TYPE_ARRAY:
diff --git a/src/compiler/sema_types.c b/src/compiler/sema_types.c
index 674bbe1eb..ed42fb45e 100644
--- a/src/compiler/sema_types.c
+++ b/src/compiler/sema_types.c
@@ -78,7 +78,15 @@ static inline bool sema_resolve_array_type(Context *context, TypeInfo *type, boo
 			return type_info_poison(type);
 		}
 	}
-
+	Type *distinct_base = type_flatten_distinct(type->array.base->type);
+	if (distinct_base->type_kind == TYPE_STRUCT)
+	{
+		if (distinct_base->decl->has_variable_array)
+		{
+			SEMA_ERROR(type, "Arrays of structs with flexible array members is not allowed.");
+			return type_info_poison(type);
+		}
+	}
 	switch (type->kind)
 	{
 		case TYPE_INFO_SUBARRAY:
@@ -105,6 +113,7 @@ static inline bool sema_resolve_array_type(Context *context, TypeInfo *type, boo
 			UNREACHABLE
 	}
 	assert(!type->array.len || type->array.len->expr_kind == EXPR_CONST);
+	if (type->array.base)
 	type->resolve_status = RESOLVE_DONE;
 	return true;
 }
@@ -211,6 +220,7 @@ bool sema_resolve_type(Context *context, Type *type)
 		case TYPE_ARRAY:
 		case TYPE_SUBARRAY:
 		case TYPE_INFERRED_ARRAY:
+		case TYPE_FLEXIBLE_ARRAY:
 			return sema_resolve_type(context, type->array.base);
 		case TYPE_FAILABLE:
 			return sema_resolve_type(context, type->failable);
diff --git a/src/compiler/types.c b/src/compiler/types.c
index 2f0c545cd..f6db854b5 100644
--- a/src/compiler/types.c
+++ b/src/compiler/types.c
@@ -51,9 +51,10 @@ static AlignSize max_alignment_vector;
 
 #define PTR_OFFSET 0
 #define INFERRED_ARRAY_OFFSET 1
-#define SUB_ARRAY_OFFSET 2
-#define FAILABLE_OFFSET 3
-#define ARRAY_OFFSET 4
+#define FLEXIBLE_ARRAY_OFFSET 2
+#define SUB_ARRAY_OFFSET 3
+#define FAILABLE_OFFSET 4
+#define ARRAY_OFFSET 5
 
 Type *type_cint(void)
 {
@@ -149,6 +150,7 @@ const char *type_to_error_string(Type *type)
 			asprintf(&buffer, "%s[%llu]", type_to_error_string(type->array.base), (unsigned long long)type->array.len);
 			return buffer;
 		case TYPE_INFERRED_ARRAY:
+		case TYPE_FLEXIBLE_ARRAY:
 			asprintf(&buffer, "%s[*]", type_to_error_string(type->array.base));
 			return buffer;
 		case TYPE_SUBARRAY:
@@ -207,6 +209,8 @@ RETRY:
 		}
 		case CT_TYPES:
 			UNREACHABLE;
+		case TYPE_FLEXIBLE_ARRAY:
+			return 0;
 		case TYPE_FAILABLE:
 			type = type->failable;
 			goto RETRY;
@@ -315,6 +319,7 @@ bool type_is_abi_aggregate(Type *type)
 		case TYPE_TYPEINFO:
 		case TYPE_INFERRED_ARRAY:
 		case TYPE_UNTYPED_LIST:
+		case TYPE_FLEXIBLE_ARRAY:
 			UNREACHABLE
 	}
 	UNREACHABLE
@@ -446,6 +451,7 @@ AlignSize type_abi_alignment(Type *type)
 			return t.iptr.canonical->builtin.abi_alignment;
 		case TYPE_ARRAY:
 		case TYPE_INFERRED_ARRAY:
+		case TYPE_FLEXIBLE_ARRAY:
 			type = type->array.base;
 			goto RETRY;
 		case TYPE_SUBARRAY:
@@ -565,6 +571,33 @@ static Type *type_generate_inferred_array(Type *arr_type, bool canonical)
 	return arr;
 }
 
+static Type *type_generate_flexible_array(Type *arr_type, bool canonical)
+{
+	if (canonical) arr_type = arr_type->canonical;
+	if (!arr_type->type_cache)
+	{
+		create_type_cache(arr_type);
+	}
+
+	Type *arr = arr_type->type_cache[FLEXIBLE_ARRAY_OFFSET];
+	if (arr == NULL)
+	{
+		arr = type_new(TYPE_FLEXIBLE_ARRAY, strformat("%s[*]", arr_type->name));
+		arr->array.base = arr_type;
+		arr->array.len = 0;
+		arr_type->type_cache[FLEXIBLE_ARRAY_OFFSET] = arr;
+		if (arr_type == arr_type->canonical)
+		{
+			arr->canonical = arr;
+		}
+		else
+		{
+			arr->canonical = type_generate_flexible_array(arr_type->canonical, true);
+		}
+	}
+	return arr;
+}
+
 
 Type *type_get_ptr_recurse(Type *ptr_type)
 {
@@ -599,6 +632,11 @@ Type *type_get_inferred_array(Type *arr_type)
 	return type_generate_inferred_array(arr_type, false);
 }
 
+Type *type_get_flexible_array(Type *arr_type)
+{
+	return type_generate_flexible_array(arr_type, false);
+}
+
 static inline bool array_structurally_equivalent_to_struct(Type *array, Type *type)
 {
 	assert(array->type_kind == TYPE_ARRAY);
@@ -716,6 +754,7 @@ Type *type_get_indexed_type(Type *type)
 		case TYPE_ARRAY:
 		case TYPE_SUBARRAY:
 		case TYPE_INFERRED_ARRAY:
+		case TYPE_FLEXIBLE_ARRAY:
 		case TYPE_VECTOR:
 			return type->array.base;
 		case TYPE_DISTINCT:
@@ -895,6 +934,9 @@ static void type_append_name_to_scratch(Type *type)
 		case TYPE_SUBARRAY:
 			type_append_name_to_scratch(type->pointer);
 			scratch_buffer_append("[]");
+		case TYPE_FLEXIBLE_ARRAY:
+			type_append_name_to_scratch(type->pointer);
+			scratch_buffer_append("[*]");
 		case TYPE_VOID:
 		case TYPE_BOOL:
 		case TYPE_I8:
@@ -1078,6 +1120,7 @@ bool type_is_scalar(Type *type)
 		case TYPE_VECTOR:
 		case TYPE_FAILABLE_ANY:
 		case TYPE_ANY:
+		case TYPE_FLEXIBLE_ARRAY:
 			return false;
 		case TYPE_BOOL:
 		case ALL_INTS:
@@ -1355,6 +1398,7 @@ Type *type_find_max_type(Type *type, Type *other)
 		case TYPE_TYPEINFO:
 		case TYPE_ANY:
 		case TYPE_BITSTRUCT:
+		case TYPE_FLEXIBLE_ARRAY:
 			return NULL;
 		case ALL_INTS:
 			if (other->type_kind == TYPE_DISTINCT && type_underlying_is_numeric(other)) return other;
diff --git a/test/test_suite/bitstruct/embedded_bitstruct.c3t b/test/test_suite/bitstruct/embedded_bitstruct.c3t
index 7cb21407b..59d7b3954 100644
--- a/test/test_suite/bitstruct/embedded_bitstruct.c3t
+++ b/test/test_suite/bitstruct/embedded_bitstruct.c3t
@@ -11,12 +11,6 @@ struct Bar
         {
             int y;
         }
-        struct
-        {}
-        union
-        {
-            struct {  }
-        }
     }
     bitstruct : uint
     {
@@ -68,20 +62,20 @@ entry:
   %8 = ashr i32 %7, 23
   call void (i8*, ...) @printf(i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str, i32 0, i32 0), i32 %4, i32 %8)
   %9 = bitcast %Foo* %f to i8*
-  call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 %9, i8* align 4 bitcast (%Foo* @.__const.8 to i8*), i32 16, i1 false)
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 %9, i8* align 4 bitcast (%Foo* @.__const.5 to i8*), i32 16, i1 false)
   %10 = getelementptr inbounds %Foo, %Foo* %f, i32 0, i32 0
-  %11 = getelementptr inbounds %anon.4, %anon.4* %10, i32 0, i32 0
-  %12 = getelementptr inbounds %anon.5, %anon.5* %11, i32 0, i32 0
+  %11 = getelementptr inbounds %anon.1, %anon.1* %10, i32 0, i32 0
+  %12 = getelementptr inbounds %anon.2, %anon.2* %11, i32 0, i32 0
   %13 = load i32, i32* %12, align 4
   %14 = getelementptr inbounds %Foo, %Foo* %f, i32 0, i32 0
-  %15 = getelementptr inbounds %anon.4, %anon.4* %14, i32 0, i32 1
-  %16 = getelementptr inbounds %anon.6, %anon.6* %15, i32 0, i32 0
+  %15 = getelementptr inbounds %anon.1, %anon.1* %14, i32 0, i32 1
+  %16 = getelementptr inbounds %anon.3, %anon.3* %15, i32 0, i32 0
   %17 = load i32, i32* %16, align 4
   %18 = getelementptr inbounds %Foo, %Foo* %f, i32 0, i32 0
-  %19 = getelementptr inbounds %anon.4, %anon.4* %18, i32 0, i32 2
+  %19 = getelementptr inbounds %anon.1, %anon.1* %18, i32 0, i32 2
   %20 = load i32, i32* %19, align 4
   %21 = getelementptr inbounds %Foo, %Foo* %f, i32 0, i32 1
   %22 = load i32, i32* %21, align 4
-  call void (i8*, ...) @printf(i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str.9, i32 0, i32 0), i32 %13, i32 %17, i32 %20, i32 %22)
+  call void (i8*, ...) @printf(i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str.6, i32 0, i32 0), i32 %13, i32 %17, i32 %20, i32 %22)
   ret void
 }
diff --git a/test/test_suite/bitstruct/invalid_empty_struct_union.c3 b/test/test_suite/bitstruct/invalid_empty_struct_union.c3
new file mode 100644
index 000000000..d51661a07
--- /dev/null
+++ b/test/test_suite/bitstruct/invalid_empty_struct_union.c3
@@ -0,0 +1,7 @@
+struct Foo // #error: Zero sized structs are not permitted.
+{
+}
+
+union Bar // #error: Zero sized unions are not permitted.
+{
+}
\ No newline at end of file
diff --git a/test/test_suite/compile_time_introspection/defined_err.c3 b/test/test_suite/compile_time_introspection/defined_err.c3
index 59f9e8aca..27d9bbf03 100644
--- a/test/test_suite/compile_time_introspection/defined_err.c3
+++ b/test/test_suite/compile_time_introspection/defined_err.c3
@@ -4,7 +4,9 @@ fn void test1()
 }
 
 struct Foo
-{}
+{
+    int x;
+}
 
 fn void test2()
 {
diff --git a/test/test_suite/compile_time_introspection/nameof.c3t b/test/test_suite/compile_time_introspection/nameof.c3t
index 0d9656cb4..f795a2b83 100644
--- a/test/test_suite/compile_time_introspection/nameof.c3t
+++ b/test/test_suite/compile_time_introspection/nameof.c3t
@@ -3,7 +3,7 @@ module mymodule;
 
 extern fn void printf(char *, ...);
 
-struct Foo { }
+struct Foo { int y; }
 
 int b;
 
diff --git a/test/test_suite/define/forbidden_defines.c3 b/test/test_suite/define/forbidden_defines.c3
new file mode 100644
index 000000000..78fc1ce82
--- /dev/null
+++ b/test/test_suite/define/forbidden_defines.c3
@@ -0,0 +1,3 @@
+define Abc = int[*]; // #error: Inferred array types can only be used in declarations with initializers.
+define Bcd = anyerr; // #error: 'anyerr' may not be aliased.
+define Efd = variant; // #error: 'variant' may not be aliased.
diff --git a/test/test_suite/expressions/no_valid_conversion_minus.c3 b/test/test_suite/expressions/no_valid_conversion_minus.c3
index 30c91a85a..68ad6a1c1 100644
--- a/test/test_suite/expressions/no_valid_conversion_minus.c3
+++ b/test/test_suite/expressions/no_valid_conversion_minus.c3
@@ -1,5 +1,5 @@
 struct Foo
-{}
+{ int j; }
 
 fn int main()
 {
diff --git a/test/test_suite/from_docs/examples_struct.c3 b/test/test_suite/from_docs/examples_struct.c3
index 065e4de8c..dccc7d404 100644
--- a/test/test_suite/from_docs/examples_struct.c3
+++ b/test/test_suite/from_docs/examples_struct.c3
@@ -1,6 +1,6 @@
 define Callback = fn int(char c);
-struct Person {}
-struct Company {}
+struct Person { int i; }
+struct Company { int j; }
 enum Status : int
 {
     IDLE,
diff --git a/test/test_suite/macro_methods/access.c3 b/test/test_suite/macro_methods/access.c3
index cc29bc6b7..07f22dc87 100644
--- a/test/test_suite/macro_methods/access.c3
+++ b/test/test_suite/macro_methods/access.c3
@@ -10,6 +10,7 @@ struct An3
 
 struct An2
 {
+    int z;
 }
 
 extern fn void printf(char *string);
diff --git a/test/test_suite/macro_methods/macro_method_fails.c3 b/test/test_suite/macro_methods/macro_method_fails.c3
index 697a570e6..d1f10338a 100644
--- a/test/test_suite/macro_methods/macro_method_fails.c3
+++ b/test/test_suite/macro_methods/macro_method_fails.c3
@@ -10,6 +10,7 @@ struct An3
 
 struct An2
 {
+    int y;
 }
 
 extern fn void printf(char* string);
diff --git a/test/test_suite/struct/flex_array_struct_err.c3 b/test/test_suite/struct/flex_array_struct_err.c3
new file mode 100644
index 000000000..59faccf3b
--- /dev/null
+++ b/test/test_suite/struct/flex_array_struct_err.c3
@@ -0,0 +1,31 @@
+struct Foo
+{
+    int x;
+    int[*] y; // #error: flexible array member must be the last element
+    int z;
+}
+
+struct Bar
+{
+    int[*] y; // #error: flexible array member cannot be the only element
+}
+
+struct Baz
+{
+    int y;
+    int[*] z;
+}
+
+struct BazContainerOk
+{
+    int z;
+    Baz c;
+}
+
+struct BazContainer
+{
+    Baz c; // #error: A struct member with a flexible array must be the last element.
+    int y;
+}
+
+Baz[5] ab; // #error: Arrays of structs with flexible array members is not allowed.
\ No newline at end of file
diff --git a/test/test_suite/struct/struct_codegen_fam.c3t b/test/test_suite/struct/struct_codegen_fam.c3t
new file mode 100644
index 000000000..6ab354811
--- /dev/null
+++ b/test/test_suite/struct/struct_codegen_fam.c3t
@@ -0,0 +1,35 @@
+// #target: x64-darwin
+module foo;
+
+struct Bar
+{
+    struct
+    {
+        int y;
+    }
+    int ufe;
+    int[*] z;
+}
+
+
+fn void test(Bar b)
+{
+    b.z[1];
+}
+
+/* #expect: foo.ll
+
+%Bar = type { %anon, i32, [0 x i32] }
+%anon = type { i32 }
+
+define void @foo.test(%Bar* byval(%Bar) align 8 %0) #0 {
+entry:
+  %b = alloca %Bar, align 4
+  %1 = bitcast %Bar* %b to i8*
+  %2 = bitcast %Bar* %0 to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 %1, i8* align 8 %2, i32 8, i1 false)
+  %3 = getelementptr inbounds %Bar, %Bar* %b, i32 0, i32 2
+  %4 = getelementptr inbounds [0 x i32], [0 x i32]* %3, i64 0, i64 1
+  %5 = load i32, i32* %4, align 4
+  ret void
+}
\ No newline at end of file
diff --git a/test/test_suite/struct/zero_member.c3 b/test/test_suite/struct/zero_member.c3
new file mode 100644
index 000000000..fb5c145ad
--- /dev/null
+++ b/test/test_suite/struct/zero_member.c3
@@ -0,0 +1,7 @@
+define Foo = int[0];
+
+struct Bar
+{
+    Foo x; // #error: Zero length arrays are not valid members.
+    int b;
+}
\ No newline at end of file
diff --git a/test/test_suite/union/flexible_array_union.c3 b/test/test_suite/union/flexible_array_union.c3
new file mode 100644
index 000000000..42bbe8276
--- /dev/null
+++ b/test/test_suite/union/flexible_array_union.c3
@@ -0,0 +1,5 @@
+union Zee
+{
+    int z;
+    int[*] y; // #error: Flexible array members not allowed in unions.
+}
\ No newline at end of file
diff --git a/test/test_suite/union/empty_unions.c3 b/test/test_suite/union/test_unions.c3
similarity index 89%
rename from test/test_suite/union/empty_unions.c3
rename to test/test_suite/union/test_unions.c3
index a22d5734d..8f465442b 100644
--- a/test/test_suite/union/empty_unions.c3
+++ b/test/test_suite/union/test_unions.c3
@@ -1,7 +1,5 @@
 module test;
 
-struct Empty {}
-union Foo {}
 union Qu
 {
     Qu *x;