Test that evaluation returns the same results in syntax and IR.

src/eval.rs

@@ -0,0 +1,15 @@
+mod env;
+mod primop;
+mod value;
+
+pub use env::{EvalEnvironment, LookupError};
+pub use primop::PrimOpError;
+pub use value::Value;
+
+#[derive(Clone, Debug, PartialEq, thiserror::Error)]
+pub enum EvalError {
+    #[error(transparent)]
+    Lookup(#[from] LookupError),
+    #[error(transparent)]
+    PrimOp(#[from] PrimOpError),
+}