Fix to not duplicate arg labels on constrained sketches (#6337)

src/lang/modifyAst.ts

@@ -227,6 +227,8 @@ export function addSketchTo(
 Set the keyword argument to the given value.
 Returns true if it overwrote an existing argument.
 Returns false if no argument with the label existed before.
+Returns 'no-mutate' if the label was found, but the value is constrained and not
+mutated.
 Also do some checks to see if it's actually trying to set a constraint on
 a sketch line that's already fully constrained, and if so, duplicates the arg.
 WILL BE FIXED SOON.
@@ -235,7 +237,7 @@ export function mutateKwArg(
   label: string,
   node: CallExpressionKw,
   val: Expr
-): boolean {
+): boolean | 'no-mutate' {
   for (let i = 0; i < node.arguments.length; i++) {
     const arg = node.arguments[i]
     if (arg.label.name === label) {
@@ -254,6 +256,8 @@ export function mutateKwArg(
         })
         return true
       }
+      // The label was found, but the value is not a literal or static.
+      return 'no-mutate'
     }
   }
   node.arguments.push(createLabeledArg(label, val))