feat: new Error not a constant

crates/uplc/src/machine/error.rs

@@ -12,13 +12,13 @@ pub enum Error {
     OutOfExError(ExBudget),
     #[error("Invalid Stepkind: {0}")]
     InvalidStepKind(u8),
-    #[error("Cannot evaluate an open term: {0:#?}")]
+    #[error("Cannot evaluate an open term:\n\n{0:#?}")]
     OpenTermEvaluated(Term<NamedDeBruijn>),
     #[error("The provided Plutus code called 'error'.")]
     EvaluationFailure,
-    #[error("Attempted to instantiate a non-polymorphic term: {0:#?}")]
+    #[error("Attempted to instantiate a non-polymorphic term:\n\n{0:#?}")]
     NonPolymorphicInstantiation(Value),
-    #[error("Attempted to apply a non-function: {0:#?}")]
+    #[error("Attempted to apply a non-function:\n\n{0:#?}")]
     NonFunctionalApplication(Value),
     #[error("Type mismatch expected '{0}' got '{1}'")]
     TypeMismatch(Type, Type),
@@ -26,9 +26,11 @@ pub enum Error {
     UnexpectedBuiltinTermArgument(Term<NamedDeBruijn>),
     #[error("A builtin expected a term argument, but something else was received:\n\n{}\n\nYou probably have an extra force wrapped around a builtin", .0.to_pretty())]
     BuiltinTermArgumentExpected(Term<NamedDeBruijn>),
+    #[error("Unable to unlift value because it is not a constant:\n\n{0:#?}")]
+    NotAConstant(Value),
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum Type {
     Bool,
     Integer,

crates/uplc/src/machine/runtime.rs

@@ -188,13 +188,7 @@ impl DefaultFunction {
 
     pub fn check_type(&self, arg: &Value, args: &[Value]) -> Result<(), Error> {
         match self {
-            DefaultFunction::AddInteger => {
-                if arg.is_integer() {
-                    Ok(())
-                } else {
-                    Err(Error::TypeMismatch(Type::Integer, arg.into()))
-                }
-            }
+            DefaultFunction::AddInteger => arg.expect_type(Type::Integer),
             DefaultFunction::SubtractInteger => todo!(),
             DefaultFunction::MultiplyInteger => todo!(),
             DefaultFunction::DivideInteger => todo!(),
@@ -224,7 +218,7 @@ impl DefaultFunction {
             DefaultFunction::DecodeUtf8 => todo!(),
             DefaultFunction::IfThenElse => {
                 if args.is_empty() && !arg.is_bool() {
-                    Err(Error::TypeMismatch(Type::Bool, arg.into()))
+                    arg.expect_type(Type::Bool)
                 } else {
                     Ok(())
                 }