add evaluation for terms

Co-authored-by: rvcas <x@rvcas.dev>

crates/uplc/src/machine/error.rs

@@ -1,9 +1,19 @@
 use thiserror::Error;
 
-use super::ExBudget;
+use crate::ast::{NamedDeBruijn, Term};
+
+use super::{ExBudget, Value};
 
 #[derive(Error, Debug)]
 pub enum Error {
     #[error("Over budget mem: {} & cpu: {}", .0.mem, .0.cpu)]
     OutOfExError(ExBudget),
+    #[error("Invalid Stepkind: {0}")]
+    InvalidStepKind(u8),
+    #[error("Cannot evaluate an open term: {0:#?}")]
+    OpenTermEvaluated(Term<NamedDeBruijn>),
+    #[error("The provided Plutus code called 'error'.")]
+    EvaluationFailure,
+    #[error("Attempted to instantiate a non-polymorphic term: {0:#?}")]
+    NonPolymorphicInstantiation(Value),
 }