diff --git a/releasenotes.md b/releasenotes.md
index 564ea8ed2..b1a70fd9e 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -158,7 +158,8 @@
 - Anonymous bitstructs check of duplicate member names fixed.
 - Assignment to anonymous bitstruct members in structs.
 - Fix casts on empty initializers.
-- Fix to DString reserve
+- Fix to DString reserve.
+- Fix where aliases did not do arithmetic promotion.
 - @local declarations in generic modules available by accident.
 - Fixes missing checks to body arguments.
 - Do not create debug declaration for value-only parameter.
diff --git a/src/compiler/compiler.c b/src/compiler/compiler.c
index 8d759d1c4..61ddc8cff 100644
--- a/src/compiler/compiler.c
+++ b/src/compiler/compiler.c
@@ -4,6 +4,7 @@
 
 #include "compiler_internal.h"
 #include <compiler_tests/benchmark.h>
+#include "../utils/whereami.h"
 
 #define MAX_OUTPUT_FILES 1000000
 #define MAX_MODULES 100000
@@ -981,3 +982,38 @@ const char *scratch_buffer_interned(void)
 					  fnv1a(scratch_buffer.str, scratch_buffer.len), &type);
 }
 
+File *compile_and_invoke(const char *file, const char *args)
+{
+	char *name;
+	if (!file_namesplit(compiler_exe_name, &name, NULL))
+	{
+		error_exit("Failed to extract file name from '%s'", compiler_exe_name);
+	}
+	const char *compiler_path = file_append_path(find_executable_path(), name);
+	scratch_buffer_clear();
+	scratch_buffer_append(compiler_path);
+#if (_MSC_VER)
+	const char *output = "__c3_exec.exe";
+#else
+	const char *output = "__c3_exec";
+#endif
+	scratch_buffer_printf(" compile %s -o %s", file, output);
+	const char *out;
+	if (!execute_cmd_failable(scratch_buffer_to_string(), &out))
+	{
+		error_exit("Failed to compile script %s.", file);
+	}
+	DEBUG_LOG("EXEC OUT: %s", out);
+	scratch_buffer_clear();
+#if (!_MSC_VER)
+	scratch_buffer_append("./");
+#endif
+	scratch_buffer_append(output);
+	scratch_buffer_append(" ");
+	scratch_buffer_append(args);
+	if (!execute_cmd_failable(scratch_buffer_to_string(), &out))
+	{
+		error_exit("Error invoking script %s with arguments %s.", file, args);
+	}
+	return source_file_text_load(file, out);
+}
\ No newline at end of file
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index 4a03ab074..fef8084ac 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -2305,6 +2305,7 @@ File *source_file_by_id(FileId file);
 File *source_file_load(const char *filename, bool *already_loaded, const char **error);
 File *source_file_text_load(const char *filename, const char *content);
 
+File *compile_and_invoke(const char *file, const char *args);
 void compiler_parse(void);
 void emit_json(void);
 
diff --git a/src/compiler/sema_casts.c b/src/compiler/sema_casts.c
index f020c57a2..c3d712e97 100644
--- a/src/compiler/sema_casts.c
+++ b/src/compiler/sema_casts.c
@@ -2077,13 +2077,14 @@ bool cast_widen_top_down(SemaContext *context, Expr *expr, Type *type)
 Type *cast_numeric_arithmetic_promotion(Type *type)
 {
 	if (!type) return NULL;
-	switch (type->type_kind)
+	Type *canonical = type->canonical;
+	switch (canonical->type_kind)
 	{
 		case ALL_SIGNED_INTS:
-			if (type->builtin.bitsize < platform_target.width_c_int) return type_cint;
+			if (canonical->builtin.bitsize < platform_target.width_c_int) return type_cint;
 			return type;
 		case ALL_UNSIGNED_INTS:
-			if (type->builtin.bitsize < platform_target.width_c_int) return type_cuint;
+			if (canonical->builtin.bitsize < platform_target.width_c_int) return type_cuint;
 			return type;
 		case TYPE_F16:
 			// Promote F16 to a real type.
diff --git a/src/compiler/sema_passes.c b/src/compiler/sema_passes.c
index d3190d110..e790541bf 100644
--- a/src/compiler/sema_passes.c
+++ b/src/compiler/sema_passes.c
@@ -198,15 +198,21 @@ static Decl **sema_run_exec(CompilationUnit *unit, Decl *decl)
 	FOREACH_END();
 	sema_context_destroy(&context);
 	if (!success) return NULL;
-	scratch_buffer_clear();
 	if (!expr_is_const_string(filename))
 	{
 		SEMA_ERROR(filename, "A filename was expected as the first argument to '$exec'.");
 		return NULL;
 	}
-	scratch_buffer_append(filename->const_expr.bytes.ptr);
-	FOREACH_BEGIN(Expr *arg, decl->exec_decl.args)
+	scratch_buffer_clear();
+	const char *file_str = filename->const_expr.bytes.ptr;
+	bool c3_script = str_has_suffix(file_str, ".c3");
+	if (!c3_script)
+	{
+		scratch_buffer_append(file_str);
 		scratch_buffer_append(" ");
+	}
+	FOREACH_BEGIN_IDX(i, Expr *arg, decl->exec_decl.args)
+		if (i) scratch_buffer_append(" ");
 		assert(expr_is_const(arg));
 		switch (arg->const_expr.const_kind)
 		{
@@ -246,8 +252,16 @@ static Decl **sema_run_exec(CompilationUnit *unit, Decl *decl)
 		}
 		UNREACHABLE
 	FOREACH_END();
-	const char *output = execute_cmd(scratch_buffer_to_string());
-	File *file = source_file_text_load(scratch_buffer_to_string(), output);
+	File *file;
+	if (c3_script)
+	{
+		file = compile_and_invoke(file_str, scratch_buffer_copy());
+	}
+	else
+	{
+		const char *output = execute_cmd(scratch_buffer_to_string());
+		file = source_file_text_load(scratch_buffer_to_string(), output);
+	}
 	if (global_context.includes_used++ > MAX_INCLUDES)
 	{
 		SEMA_ERROR(decl, "This $include would cause the maximum number of includes (%d) to be exceeded.", MAX_INCLUDES);
diff --git a/src/main.c b/src/main.c
index ee7317e49..0dba24b8e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -22,9 +22,11 @@ static void cleanup()
 	memory_release();
 }
 
+const char *compiler_exe_name;
 
 int main_real(int argc, const char *argv[])
 {
+	compiler_exe_name = argv[0];
 	bench_begin();
 
 	// Setjmp will allow us to add things like fuzzing with
diff --git a/src/utils/file_utils.c b/src/utils/file_utils.c
index 9d6431c6b..1d7d53cbf 100644
--- a/src/utils/file_utils.c
+++ b/src/utils/file_utils.c
@@ -611,6 +611,46 @@ const char *execute_cmd(const char *cmd)
 	return str_trim(output);
 }
 
+bool execute_cmd_failable(const char *cmd, const char **result)
+{
+	char buffer[BUFSIZE];
+	char *output = "";
+	FILE *process = NULL;
+#if (_MSC_VER)
+	if (!(process = _wpopen(win_utf8to16(cmd), L"r"))) return false;
+#else
+	if (!(process = popen(cmd, "r"))) return false;
+#endif
+	while (fgets(buffer, BUFSIZE - 1, process))
+	{
+		output = str_cat(output, buffer);
+	}
+#if PLATFORM_WINDOWS
+	int err = _pclose(process);
+#else
+	int err = pclose(process);
+#endif
+	if (err) return false;
+
+	while (output[0] != 0)
+	{
+		switch (output[0])
+		{
+			case ' ':
+			case '\t':
+			case '\n':
+			case '\r':
+				output++;
+				continue;
+			default:
+				break;
+		}
+		break;
+	}
+	*result = str_trim(output);
+	return true;
+}
+
 #if PLATFORM_WINDOWS
 
 char *realpath(const char *path, char *const resolved_path)
diff --git a/src/utils/lib.h b/src/utils/lib.h
index dcc707c99..679b87c3d 100644
--- a/src/utils/lib.h
+++ b/src/utils/lib.h
@@ -15,6 +15,8 @@
 const char *download_file(const char *url, const char *resource, const char *file_path);
 #endif
 
+extern const char *compiler_exe_name;
+
 typedef struct StringSlice_
 {
 	const char *ptr;
@@ -84,6 +86,7 @@ void file_add_wildcard_files(const char ***files, const char *path, bool recursi
 const char *file_append_path(const char *path, const char *name);
 
 const char *execute_cmd(const char *cmd);
+bool execute_cmd_failable(const char *cmd, const char **result);
 void *cmalloc(size_t size);
 void *ccalloc(size_t size, size_t elements);
 void memory_init(void);
diff --git a/src/version.h b/src/version.h
index fbe02ff0f..d6b603ef9 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1 +1 @@
-#define COMPILER_VERSION "0.4.601"
\ No newline at end of file
+#define COMPILER_VERSION "0.4.602"
\ No newline at end of file
diff --git a/test/test_suite/cast/cast_narrow_alias.c3t b/test/test_suite/cast/cast_narrow_alias.c3t
new file mode 100644
index 000000000..77b106e4e
--- /dev/null
+++ b/test/test_suite/cast/cast_narrow_alias.c3t
@@ -0,0 +1,31 @@
+module abc;
+def UInt8 = char;
+fn void! main()
+{
+	UInt8 x = 17;
+	UInt8 y = 5;
+	UInt8 z = (x >> y) & 0x1;
+}
+/* #expect: abc.ll
+
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-darwin"
+; Function Attrs: nounwind
+define i64 @abc.main() #0 {
+entry:
+  %x = alloca i8, align 1
+  %y = alloca i8, align 1
+  %z = alloca i8, align 1
+  store i8 17, ptr %x, align 1
+  store i8 5, ptr %y, align 1
+  %0 = load i8, ptr %x, align 1
+  %zext = zext i8 %0 to i32
+  %1 = load i8, ptr %y, align 1
+  %zext1 = zext i8 %1 to i32
+  %lshr = lshr i32 %zext, %zext1
+  %2 = freeze i32 %lshr
+  %and = and i32 %2, 1
+  %trunc = trunc i32 %and to i8
+  store i8 %trunc, ptr %z, align 1
+  ret i64 0
+}