Enumerate severity on problem variants

crates/compiler/problem/src/lib.rs

@@ -3,3 +3,15 @@
 // See github.com/roc-lang/roc/issues/800 for discussion of the large_enum_variant check.
 #![allow(clippy::large_enum_variant)]
 pub mod can;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Severity {
+    /// This will cause a runtime error if some code get srun
+    /// (e.g. type mismatch, naming error)
+    RuntimeError,
+
+    /// This will never cause the code to misbehave,
+    /// but should be cleaned up
+    /// (e.g. unused def, unused import)
+    Warning,
+}