diff --git a/resources/examples/guess_number.c3 b/resources/examples/guess_number.c3
new file mode 100644
index 000000000..f9abc9529
--- /dev/null
+++ b/resources/examples/guess_number.c3
@@ -0,0 +1,95 @@
+module guess_number;
+import std::mem;
+import std::io;
+import libc;
+
+extern fn void printf(char*, ...);
+extern fn isize getline(char** linep, usize* linecapp, CFile stream);
+
+struct Game
+{
+    int answer;
+    bool done;
+    int guesses;
+    int high;
+}
+
+optnum InputResult
+{
+    NOT_AN_INT,
+    FAILED_TO_READ,
+}
+
+int err_count = 0;
+
+fn int! askGuess(int high)
+{
+    printf("Guess a number between 1 and %d: ", high);
+    char[] text = readLine()?;
+    char* end = null;
+    int value = (int)libc::strtol(text.ptr, &end, 10);
+    if (end && end[0] >= ' ') return InputResult.NOT_AN_INT!;
+    return value;
+}
+
+fn char[]! readLine()
+{
+    char* chars = mem::talloc(1024)?;
+    isize loaded = getline(&chars, &&(usize)1023, @libc::stdin());
+    if (loaded < 0) return InputResult.FAILED_TO_READ!;
+    chars[loaded] = 0;
+    return chars[0..(loaded - 1)];
+}
+
+fn int! askGuessMulti(int high)
+ {
+    while (true)
+    {
+        int! result = askGuess(high);
+        if (catch(result) == InputResult.NOT_AN_INT)
+        {
+          printf("I didn't understand that.\n");
+          err_count++;
+          continue;
+        }
+        return result;
+    }
+    $unreachable;
+}
+
+fn void! Game.play(Game *game)
+{
+    while (!game.done)
+    {
+        int guess = askGuessMulti(game.high)?;
+        game.report(guess);
+        game.update(guess);
+    }
+}
+
+fn void Game.report(Game *game, int guess)
+{
+    char[] desc = {|
+        if (guess < game.answer) return "too low";
+        if (guess > game.answer) return "too high";
+        return "the answer";
+    |};
+    printf("%d is %.*s.\n", guess, (int)desc.len, desc.ptr);
+}
+
+fn void Game.update(Game *game, int guess)
+{
+    if (guess == game.answer) game.done = true;
+    game.guesses++;
+}
+
+fn void! main()
+{
+    libc::srand((int)libc::clock());
+    int high = 100;
+    int answer = libc::rand() % high + 1;
+    Game game = { .answer = answer, .high = high };
+    game.play();
+    printf("Finished in %d guesses.\n", game.guesses);
+    printf("Total input errors: %d.\n", err_count);
+}
\ No newline at end of file
diff --git a/resources/lib/std/io.c3 b/resources/lib/std/io.c3
index 718d878b1..8b336d277 100644
--- a/resources/lib/std/io.c3
+++ b/resources/lib/std/io.c3
@@ -4,19 +4,18 @@
 module std::io;
 import std::mem;
 import libc;
-
-
+import std::env;
 
 struct File
 {
-    void *file;
+    CFile file;
 }
 
+
 extern fn int _puts(char* message) @extname("puts");
 extern fn int printf(char* message, ...);
 extern fn int _putchar(char c) @extname("putchar");
 
-extern File *__stdinp;
 
 fn int putchar(char c) @inline
 {
diff --git a/resources/lib/std/libc.c3 b/resources/lib/std/libc.c3
index 952cded6e..b29239b7d 100644
--- a/resources/lib/std/libc.c3
+++ b/resources/lib/std/libc.c3
@@ -9,6 +9,7 @@ import std::os::macos;
 import std::os::windows;
 // stdlib
 
+
 // Constants need to be per os/arch
 const int EXIT_FAILURE = 1;
 const int EXIT_SUCCESS = 0;
@@ -166,11 +167,11 @@ enum Errno : ErrnoType
 fn Errno errno()
 {
     $if (env::OS_TYPE == OsType.WIN32):
-        return windows::errno();
+        return (Errno)windows::errno();
     $elif (env::OS_TYPE == OsType.MACOSX):
-        return macos::errno();
+        return (Errno)macos::errno();
     $elif (env::OS_TYPE == OsType.LINUX):
-        return linux::errno();
+        return (Errno)linux::errno();
     $else:
         return Errno.ENOTRECOVERABLE;
     $endif;
@@ -181,10 +182,10 @@ define TerminateFunction = fn void();
 define CompareFunction = fn int(void*, void*);
 extern fn double atof(char* str);
 extern fn int atoi(char* str);
-extern fn long atol(char* str);
+extern fn CLongLong atoll(char* str);
 extern fn double strtod(char* str, char** endptr);
-extern fn long strtol(char* str, char** endptr, int base);
-extern fn ulong stroul(char* str, char** endptr, int base);
+extern fn CLong strtol(char* str, char** endptr, int base);
+extern fn CULong stroul(char* str, char** endptr, int base);
 extern fn void abort();
 extern fn void atexit(TerminateFunction f);
 extern fn void exit(int status);
@@ -234,6 +235,28 @@ extern fn void* realloc(void* ptr, usize size);
 
 define Fpos = long;
 define CFile = void*;
+$switch (env::OS_TYPE):
+$case OsType.LINUX:
+    extern CFile __stdin @extname("stdin");
+    extern CFile __stdout @extname("stdout");
+    extern CFile __stderr @extname("stderr");
+    macro CFile stdin() { return __stdin; }
+    macro CFile stdout() { return __stdout; }
+    macro CFile stderr() { return __stderr; }
+$case OsType.MACOSX:
+    extern CFile __stdinp;
+    extern CFile __stdoutp;
+    extern CFile __stderrp;
+    macro CFile stdin() { return __stdinp; }
+    macro CFile stdout() { return __stdoutp; }
+    macro CFile stderr() { return __stderrp; }
+$case OsType.WIN32:
+    extern fn CFile __acrt_iob_func(CInt c);
+    macro CFile stdin() { return __acrt_iob_func(0); }
+    macro CFile stdout() { return __acrt_iob_func(1); }
+    macro CFile stderr() { return __acrt_iob_func(2); }
+$default:
+$endswitch;
 
 // The following needs to be set per arch+os
 // For now I have simply pulled the defaults from MacOS
diff --git a/resources/lib/std/os/linux.c3 b/resources/lib/std/os/linux.c3
index 9c477ae66..1e738a329 100644
--- a/resources/lib/std/os/linux.c3
+++ b/resources/lib/std/os/linux.c3
@@ -10,9 +10,9 @@ fn int errno() @inline
     return *__errno_location();
 }
 
-fn void errno_set(int errno)
+fn void errno_set(int err)
 {
-    *(__errno_location()) = errno;
+    *(__errno_location()) = err;
 }
 
 $endif;
diff --git a/resources/lib/std/os/macos.c3 b/resources/lib/std/os/macos.c3
index bb543c069..5bea3eddd 100644
--- a/resources/lib/std/os/macos.c3
+++ b/resources/lib/std/os/macos.c3
@@ -2,14 +2,15 @@ module std::os::macos;
 import std::env;
 
 $if (env::OS_TYPE == OsType.MACOSX):
+
 extern fn int* __error();
 
 fn int errno() @inline
 {
     return *__error();
 }
-fn void errno_set(int errno)
+fn void errno_set(int err)
 {
-    *(__error()) = errno;
+    *(__error()) = err;
 }
 $endif;
diff --git a/resources/lib/std/os/windows.c3 b/resources/lib/std/os/windows.c3
index d7729920d..d634ed918 100644
--- a/resources/lib/std/os/windows.c3
+++ b/resources/lib/std/os/windows.c3
@@ -2,6 +2,7 @@ module std::os::windows;
 import std::env;
 
 $if (env::OS_TYPE == OsType.WIN32):
+
 extern fn int getLastError() @stdcall @extname("GetLastError");
 fn int errno() @inline
 {
diff --git a/src/compiler/bigint.c b/src/compiler/bigint.c
index d67078199..109d415c5 100644
--- a/src/compiler/bigint.c
+++ b/src/compiler/bigint.c
@@ -721,6 +721,23 @@ bool int_is_zero(Int op)
 	return !op.i.high && !op.i.low;
 }
 
+unsigned int_bits_needed(Int op)
+{
+	TypeKind kind = op.type;
+	Int128 i = op.i;
+	int bits_used;
+	if (type_kind_is_signed(kind))
+	{
+		if (i128_is_neg(i))
+		{
+			i = i128_neg(i);
+			i = i128_sub64(i, 1);
+		}
+		return (unsigned) (1 + 128 - i128_clz(&i));
+	}
+	return  (unsigned) (128 - i128_clz(&i));
+}
+
 Int int_add(Int op1, Int op2)
 {
 	assert(op1.type == op2.type);
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index 0bba3dfe9..effae5064 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -56,6 +56,7 @@ typedef struct TypeInfo_ TypeInfo;
 typedef struct Expr_ Expr;
 typedef struct Module_ Module;
 typedef struct Type_ Type;
+typedef Type CanonicalType;
 
 typedef unsigned AstId;
 
@@ -259,7 +260,7 @@ typedef struct
 struct Type_
 {
 	TypeKind type_kind;
-	Type *canonical;
+	CanonicalType *canonical;
 	const char *name;
 	Type **type_cache;
 	void *backend_type;
@@ -1428,7 +1429,9 @@ typedef struct
 
 typedef struct SemaContext_
 {
+	// Evaluated in this.
 	CompilationUnit *unit;
+	// Compiled in this unit.
 	CompilationUnit *compilation_unit;
 	Decl *current_function;
 	Decl *current_macro;
@@ -1709,6 +1712,7 @@ bool int_comp(Int op1, Int op2, BinaryOp op);
 uint64_t int_to_u64(Int op);
 int64_t int_to_i64(Int op);
 bool int_is_zero(Int op);
+unsigned int_bits_needed(Int op);
 bool int_fits(Int op1, TypeKind kind);
 Int int_rightmost_bits(Int op, unsigned to_bits, TypeKind result_type);
 Int int_conv(Int op, TypeKind to_type);
@@ -1851,7 +1855,9 @@ const char *decl_to_name(Decl *decl);
 
 static inline Decl *decl_raw(Decl *decl);
 static inline bool decl_ok(Decl *decl) { return !decl || decl->decl_kind != DECL_POISONED; }
-static inline bool decl_poison(Decl *decl) { decl->decl_kind = DECL_POISONED; decl->resolve_status = RESOLVE_DONE; return false; }
+static inline bool decl_poison(Decl *decl) {
+	decl->decl_kind = DECL_POISONED; decl->resolve_status = RESOLVE_DONE; return false;
+}
 static inline bool decl_is_struct_type(Decl *decl);
 static inline bool decl_is_callable_type(Decl *decl);
 static inline bool decl_is_user_defined_type(Decl *decl);
@@ -2112,6 +2118,8 @@ static inline bool type_is_integer_or_bool_kind(Type *type);
 static inline bool type_is_numeric(Type *type);
 static inline bool type_underlying_is_numeric(Type *type);
 static inline bool type_is_pointer(Type *type);
+static inline CanonicalType *type_pointer_type(Type *type);
+static inline bool type_is_arraylike(Type *type);
 static inline bool type_is_promotable_float(Type *type);
 static inline bool type_is_promotable_integer(Type *type);
 static inline bool type_is_signed(Type *type);
@@ -2128,6 +2136,7 @@ bool type_is_float_or_float_vector(Type *type);
 bool type_may_have_sub_elements(Type *type);
 static inline bool type_ok(Type *type);
 TypeSize type_size(Type *type);
+#define type_bit_size(type) (type_size(type) * 8)
 const char *type_to_error_string(Type *type);
 const char *type_quoted_error_string(Type *type);
 
@@ -2217,6 +2226,18 @@ static inline bool type_info_poison(TypeInfo *type)
 	return false;
 }
 
+static inline bool type_is_arraylike(Type *type)
+{
+	DECL_TYPE_KIND_REAL(kind, type);
+	return kind == TYPE_ARRAY || kind == TYPE_VECTOR;
+}
+
+static inline CanonicalType *type_pointer_type(Type *type)
+{
+	CanonicalType *res = type->canonical;
+	if (res->type_kind != TYPE_POINTER) return NULL;
+	return res->pointer;
+}
 
 static inline bool type_is_pointer(Type *type)
 {
diff --git a/src/compiler/context.c b/src/compiler/context.c
index a593ba5b3..e82b2ad7c 100644
--- a/src/compiler/context.c
+++ b/src/compiler/context.c
@@ -123,8 +123,7 @@ bool context_set_module(ParseContext *context, Path *path, TokenId *generic_para
 
 void unit_register_external_symbol(CompilationUnit *unit, Decl *decl)
 {
-	if (decl->decl_kind == DECL_MACRO) return;
-	assert(decl->external_name && "Missing external name");
+	if (!decl->module || decl->module == unit->module || !decl->external_name) return;
 	Decl *prev = stable_get(&unit->external_symbols, decl->external_name);
 	if (prev) return;
 	if (decl != stable_set(&unit->external_symbols, decl->external_name, decl))
diff --git a/src/compiler/number.c b/src/compiler/number.c
index 94b4f4642..e77a234e3 100644
--- a/src/compiler/number.c
+++ b/src/compiler/number.c
@@ -76,11 +76,16 @@ static inline bool compare_fps(Real left, Real right, BinaryOp op)
 bool expr_const_compare(const ExprConst *left, const ExprConst *right, BinaryOp op)
 {
 	bool is_eq;
+
 	switch (left->const_kind)
 	{
 		case CONST_BOOL:
 			return compare_bool(left->b, right->b, op);
 		case CONST_INTEGER:
+			if (right->const_kind == CONST_ENUM)
+			{
+				return int_comp(left->ixx, right->enum_val->enum_constant.expr->const_expr.ixx, op);
+			}
 			return int_comp(left->ixx, right->ixx, op);
 		case CONST_FLOAT:
 			return compare_fps(left->fxx.f, right->fxx.f, op);
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index 14499f6ea..8b4936334 100644
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -2124,7 +2124,7 @@ static bool sema_analyse_parameterized_define(SemaContext *c, Decl *decl)
 	const char *name_str = TOKSTR(name);
 	Decl *symbol = module_find_symbol(instantiated_module, name_str);
 	assert(symbol);
-	unit_register_external_symbol(c->unit, symbol);
+	unit_register_external_symbol(c->compilation_unit, symbol);
 	switch (decl->define_decl.define_kind)
 	{
 		case DEFINE_IDENT_GENERIC:
diff --git a/src/compiler/sema_expr.c b/src/compiler/sema_expr.c
index d8e8df6fd..31bc58062 100644
--- a/src/compiler/sema_expr.c
+++ b/src/compiler/sema_expr.c
@@ -14,10 +14,10 @@ static inline bool sema_expr_analyse_binary(SemaContext *context, Expr *expr);
 static inline bool sema_cast_rvalue(SemaContext *context, Expr *expr);
 static Expr *expr_access_inline_member(Expr *parent, Decl *parent_decl);
 static inline void expr_set_as_const_list(Expr *expr, ConstInitializer *list);
-static inline bool is_const(Expr *expr);
 static inline bool sema_expr_analyse_builtin(SemaContext *context, Expr *expr, bool throw_error);
 static bool sema_check_stmt_compile_time(SemaContext *context, Ast *ast);
 static bool binary_arithmetic_promotion(SemaContext *context, Expr *left, Expr *right, Type *left_type, Type *right_type, Expr *parent, const char *error_message);
+static inline bool expr_both_const(Expr *left, Expr *right);
 static inline void expr_set_as_const_list(Expr *expr, ConstInitializer *list)
 {
 	expr->expr_kind = EXPR_CONST;
@@ -27,16 +27,12 @@ static inline void expr_set_as_const_list(Expr *expr, ConstInitializer *list)
 
 static bool sema_decay_array_pointers(Expr *expr)
 {
-	Type *expr_type = expr->type->canonical;
-	if (expr_type->type_kind != TYPE_POINTER) return true;
-	switch (expr_type->pointer->type_kind)
-	{
-		case TYPE_ARRAY:
-		case TYPE_VECTOR:
-			return cast_implicit(expr, type_get_ptr(expr_type->pointer->array.base));
-		default:
-			return true;
-	}
+
+	CanonicalType *pointer_type = type_pointer_type(type_no_fail(expr->type));
+
+	if (!pointer_type || !type_is_arraylike(pointer_type)) return true;
+
+	return cast_implicit(expr, type_get_opt_fail(type_get_ptr(pointer_type->array.base), IS_FAILABLE(expr)));
 }
 
 int BINOP_PREC_REQ[BINARYOP_LAST + 1] =
@@ -71,12 +67,6 @@ static Expr *expr_access_inline_member(Expr *parent, Decl *parent_decl)
 	return embedded_struct;
 }
 
-#define IS_CONST(_x) ((_x)->expr_kind == EXPR_CONST)
-
-static inline bool is_const(Expr *expr)
-{
-	return expr->expr_kind == EXPR_CONST;
-}
 
 static inline bool expr_both_const(Expr *left, Expr *right)
 {
@@ -271,38 +261,26 @@ static inline bool expr_list_is_constant_eval(Expr **exprs, ConstantEvalKind eva
 	return true;
 }
 
+// Check if the assignment fits
 static bool sema_bit_assignment_check(Expr *right, Decl *member)
 {
-	if (right->expr_kind != EXPR_CONST || !type_is_integer(right->type)) return true;
+	// Don't check non-consts and non integers.
+	if (!IS_CONST(right) || !type_is_integer(right->type)) return true;
 
 	unsigned bits = member->var.end_bit - member->var.start_bit + 1;
 
-	if (bits >= type_size(right->type) * 8 || int_is_zero(right->const_expr.ixx)) return true;
+	// If we have enough bits to fit, then we're done.
+	if (bits >= type_bit_size(right->type) || int_is_zero(right->const_expr.ixx)) return true;
 
-	// Check that we're not assigning consts that will be cut.
-
-	TypeKind kind = right->const_expr.ixx.type;
-	Int128 i = right->const_expr.ixx.i;
-	int bits_used;
-	if (type_kind_is_signed(kind))
+	if (int_bits_needed(right->const_expr.ixx) > bits)
 	{
-		if (i128_is_neg(i))
-		{
-			i = i128_neg(i);
-			i = i128_sub64(i, 1);
-		}
-		bits_used = (int) (1 + 128 - i128_clz(&i));
+		SEMA_ERROR(right,
+				   "This constant would be truncated if stored in the bitstruct, do you need a wider bit range?");
+		return false;
 	}
-	else
-	{
-		bits_used = (int) (128 - i128_clz(&i));
-	}
-	if (bits_used <= bits) return true;
-
-	SEMA_ERROR(right,
-			   "This constant would be truncated if stored in the bitstruct, do you need a wider bit range?");
-	return false;
+	return true;
 }
+
 bool expr_is_constant_eval(Expr *expr, ConstantEvalKind eval_kind)
 {
 	RETRY:
@@ -488,7 +466,7 @@ void expr_insert_deref(Expr *original)
 }
 
 
-static void expr_unify_binary(Expr *expr, Expr *left, Expr *right)
+static void expr_unify_binary_failability(Expr *expr, Expr *left, Expr *right)
 {
 	expr->type = type_get_opt_fail(left->type, IS_FAILABLE(right));
 }
@@ -792,7 +770,7 @@ static inline bool sema_expr_analyse_ternary(SemaContext *context, Expr *expr)
 		expr_replace(expr, path ? left : right);
 	}
 
-	expr_unify_binary(expr, left, right);
+	expr_unify_binary_failability(expr, left, right);
 	return true;
 }
 
@@ -853,8 +831,6 @@ static inline bool find_possible_inferred_identifier(Type *to, Expr *expr)
 
 }
 
-
-
 static inline bool sema_expr_analyse_identifier(SemaContext *context, Type *to, Expr *expr)
 {
 	Decl *ambiguous_decl = NULL;
@@ -876,6 +852,7 @@ static inline bool sema_expr_analyse_identifier(SemaContext *context, Type *to,
 		                                  expr->identifier_expr.identifier,
 		                                  expr->identifier_expr.path,
 		                                  true);
+		(void)decl;
 		assert(!decl_ok(decl));
 		return false;
 	}
@@ -910,6 +887,7 @@ static inline bool sema_expr_analyse_identifier(SemaContext *context, Type *to,
 	{
 		if (!sema_analyse_decl(context, decl)) return decl_poison(decl);
 	}
+	unit_register_external_symbol(context->compilation_unit, decl);
 	if (decl->decl_kind == DECL_VAR)
 	{
 		decl->var.is_read = true;
@@ -2022,7 +2000,6 @@ static bool sema_analyse_body_expansion(SemaContext *macro_context, Expr *call)
 	assert(macro);
 	assert(macro->macro_decl.block_parameter.index);
 
-	// TODO handle named arguments
 	ExprCall *call_expr = &call->call_expr;
 	if (vec_size(call_expr->body_arguments))
 	{
@@ -2034,6 +2011,7 @@ static bool sema_analyse_body_expansion(SemaContext *macro_context, Expr *call)
 		SEMA_ERROR(call, "Expanding parameters is not allowed for macro invocations.");
 		return false;
 	}
+	// Theoretically we could support named arguments, but that's unnecessary.
 	unsigned expressions = vec_size(call_expr->arguments);
 	if (expressions != vec_size(macro->macro_decl.body_parameters))
 	{
@@ -2070,24 +2048,29 @@ static bool sema_analyse_body_expansion(SemaContext *macro_context, Expr *call)
 	return success;
 }
 
-bool sema_expr_analyse_general_call(SemaContext *context, Expr *expr, Decl *decl, Expr *struct_var, bool is_macro, bool failable)
+static inline bool sema_analyse_call_attributes(SemaContext *context, Decl *decl, Expr *call_expr)
 {
+	Attr **attributes = call_expr->call_expr.attributes;
 	int force_inline = -1;
-	VECEACH(expr->call_expr.attributes, i)
+	VECEACH(attributes, i)
 	{
-		Attr *attr = expr->call_expr.attributes[i];
+		Attr *attr = attributes[i];
 		AttributeType attribute = sema_analyse_attribute(context, attr, ATTR_CALL);
-		if (attribute == ATTRIBUTE_NONE) return expr_poison(expr);
-
-		bool had = false;
+		if (attribute == ATTRIBUTE_NONE) return false;
 		switch (attribute)
 		{
 			case ATTRIBUTE_INLINE:
 			case ATTRIBUTE_NOINLINE:
-				if (decl->decl_kind != DECL_FUNC)
+				if (decl && decl->decl_kind != DECL_FUNC)
 				{
-					SEMA_TOKID_ERROR(attr->name, "Inline / noinline attribute is only allowed for direct function/method calls");
-					return expr_poison(expr);
+					SEMA_TOKID_ERROR(attr->name,
+					                 "Inline / noinline attribute is only allowed for direct function/method calls");
+					return false;
+				}
+				if (force_inline != -1)
+				{
+					SEMA_TOKID_ERROR(attr->name, "Only a single inline / noinline attribute is allowed on a call.");
+					return false;
 				}
 				force_inline = attribute == ATTRIBUTE_INLINE ? 1 : 0;
 				break;
@@ -2095,7 +2078,17 @@ bool sema_expr_analyse_general_call(SemaContext *context, Expr *expr, Decl *decl
 				UNREACHABLE;
 		}
 	}
+	if (force_inline != -1)
+	{
+		call_expr->call_expr.force_inline = force_inline == 1;
+		call_expr->call_expr.force_noinline = force_inline == 0;
+	}
+	return true;
+}
+bool sema_expr_analyse_general_call(SemaContext *context, Expr *expr, Decl *decl, Expr *struct_var, bool is_macro, bool failable)
+{
 	expr->call_expr.is_type_method = struct_var != NULL;
+	if (!sema_analyse_call_attributes(context, decl, expr)) return expr_poison(expr);
 	if (decl == NULL)
 	{
 		return sema_expr_analyse_var_call(context, expr, type_flatten_distinct_failable(expr->call_expr.function->type), failable);
@@ -2125,8 +2118,6 @@ bool sema_expr_analyse_general_call(SemaContext *context, Expr *expr, Decl *decl
 				return false;
 			}
 			expr->call_expr.func_ref = decl;
-			expr->call_expr.force_inline = force_inline == 1;
-			expr->call_expr.force_noinline = force_inline == 0;
 			return sema_expr_analyse_func_call(context, expr, decl, struct_var, failable);
 		case DECL_GENERIC:
 			if (is_macro)
@@ -4770,7 +4761,7 @@ static bool sema_expr_analyse_add(SemaContext *context, Expr *expr, Expr *left,
 	}
 
 	// 6. Set the type & other properties.
-	expr_unify_binary(expr, left, right);
+	expr_unify_binary_failability(expr, left, right);
 
 	return true;
 
@@ -4953,7 +4944,7 @@ static bool sema_expr_analyse_bit(SemaContext *context, Expr *expr, Expr *left,
 	}
 
 	// 5. Assign the type
-	expr_unify_binary(expr, left, right);
+	expr_unify_binary_failability(expr, left, right);
 	return true;
 }
 
@@ -5122,9 +5113,9 @@ static void cast_to_max_bit_size(SemaContext *context, Expr *left, Expr *right,
 static bool sema_is_unsigned_always_false_comparison(SemaContext *context, Expr *expr, Expr *left, Expr *right)
 {
 	if (context->active_scope.flags & SCOPE_MACRO) return true;
-	if (!is_const(left) && !is_const(right)) return true;
+	if (!expr_is_const(left) && !expr_is_const(right)) return true;
 	if (!type_is_integer(left->type)) return true;
-	if (is_const(left) && type_is_unsigned(type_flatten_distinct(right->type)))
+	if (expr_is_const(left) && type_is_unsigned(type_flatten_distinct(right->type)))
 	{
 		if (int_is_neg(left->const_expr.ixx))
 		{
@@ -5146,7 +5137,7 @@ static bool sema_is_unsigned_always_false_comparison(SemaContext *context, Expr
 				return true;
 		}
 	}
-	if (!is_const(right) || !type_is_unsigned(type_flatten_distinct(left->type))) return true;
+	if (!expr_is_const(right) || !type_is_unsigned(type_flatten_distinct(left->type))) return true;
 	if (int_is_neg(right->const_expr.ixx))
 	{
 		SEMA_ERROR(right, "Comparing an unsigned value with a negative constant is only allowed inside of macros.");
@@ -5957,7 +5948,7 @@ static inline bool sema_expr_analyse_typeid(SemaContext *context, Expr *expr)
 }
 
 
-static inline bool sema_expr_analyse_expr_block(SemaContext *context, Expr *expr)
+static inline bool sema_expr_analyse_expr_block(SemaContext *context, Type *infer_type, Expr *expr)
 {
 	bool success = true;
 	expr->type = type_void;
@@ -5965,7 +5956,7 @@ static inline bool sema_expr_analyse_expr_block(SemaContext *context, Expr *expr
 	Type *prev_expected_block_type = context->expected_block_type;
 	Ast **saved_returns = context_push_returns(context);
 	Type *stored_block_type = context->expected_block_type;
-	context->expected_block_type = NULL;
+	context->expected_block_type = infer_type;
 	SCOPE_START_WITH_FLAGS(SCOPE_EXPR_BLOCK)
 
 		PUSH_CONTINUE(NULL);
@@ -6934,7 +6925,7 @@ static inline bool sema_analyse_expr_dispatch(SemaContext *context, Expr *expr)
 		case EXPR_COMPOUND_LITERAL:
 			return sema_expr_analyse_compound_literal(context, expr);
 		case EXPR_EXPR_BLOCK:
-			return sema_expr_analyse_expr_block(context, expr);
+			return sema_expr_analyse_expr_block(context, NULL, expr);
 		case EXPR_RETHROW:
 			return sema_expr_analyse_rethrow(context, expr);
 		case EXPR_CONST:
@@ -7284,6 +7275,9 @@ bool sema_analyse_inferred_expr(SemaContext *context, Type *infer_type, Expr *ex
 		case EXPR_DESIGNATED_INITIALIZER_LIST:
 			if (!sema_expr_analyse_initializer_list(context, infer_type, expr)) return expr_poison(expr);
 			break;
+		case EXPR_EXPR_BLOCK:
+			if (!sema_expr_analyse_expr_block(context, infer_type, expr)) return expr_poison(expr);
+			break;
 		case EXPR_CONST_IDENTIFIER:
 			if (!sema_expr_analyse_identifier(context, infer_type, expr)) return expr_poison(expr);
 			break;
diff --git a/src/compiler/sema_internal.h b/src/compiler/sema_internal.h
index fad4c15a5..60530a9b7 100644
--- a/src/compiler/sema_internal.h
+++ b/src/compiler/sema_internal.h
@@ -52,6 +52,8 @@ void context_change_scope_with_flags(SemaContext *context, ScopeFlags flags);
 #define PUSH_BREAKCONT(ast) PUSH_CONTINUE(ast); PUSH_BREAK(ast)
 #define POP_BREAKCONT() POP_CONTINUE(); POP_BREAK()
 
+#define IS_CONST(_x) ((_x)->expr_kind == EXPR_CONST)
+
 AttributeType sema_analyse_attribute(SemaContext *context, Attr *attr, AttributeDomain domain);
 bool expr_is_ltype(Expr *expr);
 
@@ -71,4 +73,9 @@ bool sema_analyse_expr_lvalue(SemaContext *context, Expr *expr);
 bool sema_analyse_ct_expr(SemaContext *context, Expr *expr);
 bool sema_expr_analyse_macro_call(SemaContext *context, Expr *call_expr, Expr *struct_var, Decl *decl, bool failable);
 void expr_rewrite_to_int_const(Expr *expr_to_rewrite, Type *type, uint64_t value, bool narrowable);
+static inline bool expr_is_const(Expr *expr);
 
+static inline bool expr_is_const(Expr *expr)
+{
+	return expr->expr_kind == EXPR_CONST;
+}
diff --git a/src/compiler/sema_name_resolution.c b/src/compiler/sema_name_resolution.c
index 97de018e6..b528ce83d 100644
--- a/src/compiler/sema_name_resolution.c
+++ b/src/compiler/sema_name_resolution.c
@@ -239,10 +239,7 @@ static inline Decl *sema_resolve_symbol(SemaContext *context, const char *symbol
 		sema_report_error_on_decl(symbol_str, span, decl, ambiguous_other_decl, private_decl);
 		return poisoned_decl;
 	}
-	if (decl->module && decl->module != context->unit->module)
-	{
-		unit_register_external_symbol(context->compilation_unit, decl);
-	}
+	unit_register_external_symbol(context->compilation_unit, decl);
 	return decl;
 }
 
diff --git a/src/compiler/sema_stmts.c b/src/compiler/sema_stmts.c
index 25eb8df73..2d32bbf02 100644
--- a/src/compiler/sema_stmts.c
+++ b/src/compiler/sema_stmts.c
@@ -61,9 +61,14 @@ static inline bool sema_analyse_block_return_stmt(SemaContext *context, Ast *sta
 	context->active_scope.jump_end = true;
 	if (statement->return_stmt.expr)
 	{
-		if (!sema_analyse_expr(context, statement->return_stmt.expr))
+		Type *block_type = context->expected_block_type;
+		if (block_type)
 		{
-			return false;
+			if (!sema_analyse_expr_rhs(context, block_type, statement->return_stmt.expr, type_is_failable(block_type))) return false;
+		}
+		else
+		{
+			if (!sema_analyse_expr(context, statement->return_stmt.expr)) return false;
 		}
 	}
 	vec_add(context->returns, statement);
diff --git a/src/compiler/types.c b/src/compiler/types.c
index a3759a4bf..589412384 100644
--- a/src/compiler/types.c
+++ b/src/compiler/types.c
@@ -1552,9 +1552,10 @@ Type *type_find_max_type(Type *type, Type *other)
 		case TYPE_ERRTYPE:
 			if (other->type_kind == TYPE_ERRTYPE) return type_anyerr;
 			return NULL;
+		case TYPE_ANYERR:
+			return type_anyerr;
 		case TYPE_FUNC:
 		case TYPE_UNION:
-		case TYPE_ANYERR:
 		case TYPE_TYPEID:
 		case TYPE_STRUCT:
 		case TYPE_UNTYPED_LIST:
diff --git a/test/test_suite/macros/macro_rtype.c3 b/test/test_suite/macros/macro_rtype.c3
index bb95c1daa..e7a7aadff 100644
--- a/test/test_suite/macros/macro_rtype.c3
+++ b/test/test_suite/macros/macro_rtype.c3
@@ -1,6 +1,6 @@
 macro int frob()
 {
-    return 0.0; // #error: Expected 'int', not 'double'.
+    return 0.0; // #error: Implicitly casting 'double' to 'int' is not permitted
 }
 
 fn void test1()