js: Store value in exception

Previously, we simply had an exception enum ("TypeError" only).
This is incorrect, as all sorts of values can be thrown.

crates/js/src/bytecode/exception.rs

@@ -1,7 +1,25 @@
+use crate::Value;
+
 /// <https://262.ecma-international.org/14.0/#sec-completion-record-specification-type>
 pub type ThrowCompletionOr<T> = Result<T, Exception>;
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum Exception {
-    TypeError,
+#[derive(Clone, Debug)]
+pub struct Exception {
+    value: Value,
+}
+
+impl Exception {
+    #[must_use]
+    pub const fn new(value: Value) -> Self {
+        Self { value }
+    }
+
+    #[must_use]
+    pub fn type_error() -> Self {
+        // FIXME: This should be a "typeerror" object, but we don't
+        //        really support objects yet
+        Self {
+            value: "TypeError".to_string().into(),
+        }
+    }
 }

crates/js/src/bytecode/vm.rs

@@ -112,9 +112,8 @@ impl Vm {
                 self.set_register(*dst, result.into());
             },
             Instruction::Throw { value } => {
-                // FIXME: Actually use the value.
-                _ = value;
-                return Err(Exception::TypeError);
+                let value = self.register(*value).clone();
+                return Err(Exception::new(value));
             },
             other => todo!("Implement instruction {other:?}"),
         }

crates/js/src/value/mod.rs

@@ -246,7 +246,7 @@ impl Value {
 
         // 5. If Type(lnum) is not Type(rnum), throw a TypeError exception.
         if lnum.type_tag() != rnum.type_tag() {
-            return Err(Exception::TypeError);
+            return Err(Exception::type_error());
         }
 
         match (lnum, rnum) {
@@ -292,7 +292,7 @@ impl Value {
             },
             Self::Symbol(_) | Self::BigInt => {
                 // 2. If argument is either a Symbol or a BigInt, throw a TypeError exception.
-                Err(Exception::TypeError)
+                Err(Exception::type_error())
             },
             Self::Undefined => {
                 // 3. If argument is undefined, return NaN.
@@ -369,7 +369,7 @@ impl Value {
             },
             Self::Symbol(_) => {
                 // 2. If argument is a Symbol, throw a TypeError exception.
-                Err(Exception::TypeError)
+                Err(Exception::type_error())
             },
             Self::Undefined => {
                 // 3. If argument is undefined, return "undefined".

crates/js/src/value/object/mod.rs

@@ -136,7 +136,7 @@ impl Object {
 
         // 2. If success is false, throw a TypeError exception.
         if !success {
-            return Err(Exception::TypeError);
+            return Err(Exception::type_error());
         }
 
         // 3. Return unused.