type checking !?!?

src/ir/upper/error.rs

@@ -0,0 +1,19 @@
+use crate::common::{CompilerMsg, CompilerOutput, FileSpan};
+
+use super::{IRUProgram, Type};
+
+impl CompilerOutput {
+    pub fn check_assign(&mut self, p: &IRUProgram, src: &Type, dest: &Type, span: FileSpan) {
+        // TODO: spans
+        if src != dest {
+            self.err(CompilerMsg {
+                msg: format!(
+                    "Cannot assign type '{}' to '{}'",
+                    p.type_name(src),
+                    p.type_name(dest)
+                ),
+                spans: vec![span],
+            });
+        }
+    }
+}