Type ascription produces two incompatible fields (#7355)

# Symptoms

This code produces a big ugly confusing error in the frontend, see #7340.

# Root cause

I added a new test case, with an unknown type. In `ast.snap` under `body[0].declaration.init.ty` there two different `type` fields in the AST node for the type's name, and they have conflicting values Primitive and Identifier.

<img width="602" alt="Screenshot 2025-06-03 at 4 04 55 PM" src="https://github.com/user-attachments/assets/913a0fa0-3e8d-473f-bb64-003d44915be0" />

# Solution

Change the `enum PrimitiveType` variant from `Named(Node<Identifier>)` to `Named { name: Node<Identifier> }` so that the fields nest differently.

Now the error correctly points out to the user that the type `NotARealType` can't be found. Much better error message that shows the user the problem.

# Alternative solutions

Stop the duplicated JSON fields altogether. I tried this previously in https://github.com/KittyCAD/modeling-app/pull/4369 but it was very involved, and I didn't think it was worth it. Maybe I should reopen that PR and solve this properly.

Closes #7340

rust/kcl-lib/src/execution/types.rs

@@ -187,7 +187,7 @@ impl RuntimeType {
                 };
                 RuntimeType::Primitive(PrimitiveType::Number(ty))
             }
-            AstPrimitiveType::Named(name) => Self::from_alias(&name.name, exec_state, source_range)?,
+            AstPrimitiveType::Named { id } => Self::from_alias(&id.name, exec_state, source_range)?,
             AstPrimitiveType::Tag => RuntimeType::Primitive(PrimitiveType::Tag),
             AstPrimitiveType::ImportedGeometry => RuntimeType::Primitive(PrimitiveType::ImportedGeometry),
             AstPrimitiveType::Function(_) => RuntimeType::Primitive(PrimitiveType::Function),

rust/kcl-lib/src/parsing/ast/digest.rs

@@ -228,7 +228,7 @@ impl PrimitiveType {
         let mut hasher = Sha256::new();
         match self {
             PrimitiveType::Any => hasher.update(b"any"),
-            PrimitiveType::Named(id) => hasher.update(id.compute_digest()),
+            PrimitiveType::Named { id } => hasher.update(id.compute_digest()),
             PrimitiveType::String => hasher.update(b"string"),
             PrimitiveType::Number(suffix) => hasher.update(suffix.digestable_id()),
             PrimitiveType::Boolean => hasher.update(b"bool"),

rust/kcl-lib/src/parsing/ast/types/mod.rs

@@ -3230,7 +3230,7 @@ pub enum PrimitiveType {
     /// `fn`, type of functions.
     Function(FunctionType),
     /// An identifier used as a type (not really a primitive type, but whatever).
-    Named(Node<Identifier>),
+    Named { id: Node<Identifier> },
 }
 
 impl PrimitiveType {
@@ -3286,7 +3286,7 @@ impl fmt::Display for PrimitiveType {
                 }
                 Ok(())
             }
-            PrimitiveType::Named(n) => write!(f, "{}", n.name),
+            PrimitiveType::Named { id: n } => write!(f, "{}", n.name),
         }
     }
 }

rust/kcl-lib/src/parsing/parser.rs

@@ -2938,7 +2938,7 @@ fn primitive_type(i: &mut TokenSlice) -> ModalResult<Node<PrimitiveType>> {
         (identifier, opt(delimited(open_paren, uom_for_type, close_paren))).map(|(ident, suffix)| {
             let mut result = Node::new(PrimitiveType::Boolean, ident.start, ident.end, ident.module_id);
             result.inner =
-                PrimitiveType::primitive_from_str(&ident.name, suffix).unwrap_or(PrimitiveType::Named(ident));
+                PrimitiveType::primitive_from_str(&ident.name, suffix).unwrap_or(PrimitiveType::Named { id: ident });
             result
         }),
     ))

rust/kcl-lib/src/simulation_tests.rs

@@ -3504,3 +3504,24 @@ mod var_ref_in_own_def {
         super::execute(TEST_NAME, true).await
     }
 }
+mod ascription_unknown_type {
+    const TEST_NAME: &str = "ascription_unknown_type";
+
+    /// Test parsing KCL.
+    #[test]
+    fn parse() {
+        super::parse(TEST_NAME)
+    }
+
+    /// Test that parsing and unparsing KCL produces the original KCL input.
+    #[tokio::test(flavor = "multi_thread")]
+    async fn unparse() {
+        super::unparse(TEST_NAME).await
+    }
+
+    /// Test that KCL is executed correctly.
+    #[tokio::test(flavor = "multi_thread")]
+    async fn kcl_test_execute() {
+        super::execute(TEST_NAME, true).await
+    }
+}