feat: new Error not a constant

add_integers.uplc

@@ -1,7 +1,5 @@
 (program
   1.0.0
-  [
+  [ (force (builtin ifThenElse)) (con string "yo") (con integer 3) (con integer 4) ]
-    [ [ (force (builtin ifThenElse)) (con integer 2) ] (con integer 1) ]
-    (con string "yo")
-  ]
 )
+

crates/uplc/src/ast.rs

@@ -25,12 +25,6 @@ where
     /// We use this to apply the validator to Datum,
     /// then redeemer, then ScriptContext. If datum is
     /// even necessary (i.e. minting policy).
-    ///
-    /// ```rust
-    /// program.apply(&datum)
-    ///    .apply(&redeemer)
-    ///    .apply(&script_context);
-    /// ```
     pub fn apply(&self, program: &Self) -> Self {
         let applied_term = Term::Apply {
             function: Box::new(self.term.clone()),
@@ -86,10 +80,8 @@ pub enum Constant {
     // tag: 2
     String(String),
     // tag: 3
-    Char(char),
-    // tag: 4
     Unit,
-    // tag: 5
+    // tag: 4
     Bool(bool),
 }
 

crates/uplc/src/flat.rs

@@ -170,14 +170,6 @@ impl Encode for &Constant {
                 encode_constant(2, e)?;
                 s.encode(e)?;
             }
-            // there is no char constant tag
-            Constant::Char(c) => {
-                let mut b = [0; 4];
-
-                let s = c.encode_utf8(&mut b);
-
-                s.as_bytes().encode(e)?;
-            }
             Constant::Unit => encode_constant(3, e)?,
             Constant::Bool(b) => {
                 encode_constant(4, e)?;

crates/uplc/src/machine.rs

@@ -377,22 +377,31 @@ impl Value {
             Value::Builtin { .. } => 1,
         }
     }
+
+    pub fn expect_type(&self, r#type: Type) -> Result<(), Error> {
+        match self {
+            Value::Con(constant) => {
+                let constant_type = Type::from(constant);
+
+                if constant_type == r#type {
+                    Ok(())
+                } else {
+                    Err(Error::TypeMismatch(r#type, constant_type))
+                }
+            }
+            rest => Err(Error::NotAConstant(rest.clone())),
+        }
+    }
 }
 
-impl From<&Value> for Type {
+impl From<&Constant> for Type {
-    fn from(value: &Value) -> Self {
+    fn from(constant: &Constant) -> Self {
-        match value {
+        match constant {
-            Value::Con(constant) => match constant {
             Constant::Integer(_) => Type::Integer,
             Constant::ByteString(_) => Type::ByteString,
             Constant::String(_) => Type::String,
-                Constant::Char(_) => todo!(),
             Constant::Unit => Type::Unit,
             Constant::Bool(_) => Type::Bool,
-            },
-            Value::Delay(_) => todo!(),
-            Value::Lambda { .. } => todo!(),
-            Value::Builtin { .. } => todo!(),
         }
     }
 }

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 => {
+            DefaultFunction::AddInteger => arg.expect_type(Type::Integer),
-                if arg.is_integer() {
-                    Ok(())
-                } else {
-                    Err(Error::TypeMismatch(Type::Integer, arg.into()))
-                }
-            }
             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(())
                 }

crates/uplc/src/pretty.rs

@@ -164,7 +164,6 @@ impl Constant {
                 .append(RcDoc::text("\""))
                 .append(RcDoc::text(s))
                 .append(RcDoc::text("\"")),
-            Constant::Char(c) => unimplemented!("char: {}", c),
             Constant::Unit => RcDoc::text("unit")
                 .append(RcDoc::line())
                 .append(RcDoc::text("()")),