Swap List.mapWithIndex arg1 args order to put the element first

compiler/builtins/docs/List.roc

@@ -279,7 +279,7 @@ map4 : List a, List b, List c, List d, (a, b, c, d -> e) -> List e
 
 ## This works like [List.map], except it also passes the index
 ## of the element to the conversion function.
-mapWithIndex : List before, (Nat, before -> after) -> List after
+mapWithIndex : List before, (before, Nat -> after) -> List after
 
 ## This works like [List.map], except at any time you can return `Err` to
 ## cancel the entire operation immediately, and return that #Err.

compiler/builtins/src/std.rs

@@ -1078,14 +1078,14 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         Box::new(list_type(flex(TVAR2))),
     );
 
-    // mapWithIndex : List before, (Nat, before -> after) -> List after
+    // mapWithIndex : List before, (before, Nat -> after) -> List after
     {
         let_tvars! { cvar, before, after};
         add_top_level_function_type!(
             Symbol::LIST_MAP_WITH_INDEX,
             vec![
                 list_type(flex(before)),
-                closure(vec![nat_type(), flex(before)], cvar, Box::new(flex(after))),
+                closure(vec![flex(before), nat_type()], cvar, Box::new(flex(after))),
             ],
             Box::new(list_type(flex(after))),
         )

compiler/can/src/builtins.rs

@@ -3300,7 +3300,7 @@ fn list_map(symbol: Symbol, var_store: &mut VarStore) -> Def {
     lowlevel_2(symbol, LowLevel::ListMap, var_store)
 }
 
-/// List.mapWithIndex : List before, (Nat, before -> after) -> List after
+/// List.mapWithIndex : List before, (before, Nat -> after) -> List after
 fn list_map_with_index(symbol: Symbol, var_store: &mut VarStore) -> Def {
     lowlevel_2(symbol, LowLevel::ListMapWithIndex, var_store)
 }

compiler/gen_llvm/src/llvm/build.rs

@@ -5014,7 +5014,7 @@ fn run_higher_order_low_level<'a, 'ctx, 'env>(
             }
         }
         ListMapWithIndex { xs } => {
-            // List.mapWithIndex : List before, (Nat, before -> after) -> List after
+            // List.mapWithIndex : List before, (before, Nat -> after) -> List after
             let (list, list_layout) = load_symbol_and_layout(scope, xs);
 
             let (function, closure, closure_layout) = function_details!();

compiler/gen_llvm/src/llvm/build_list.rs

@@ -687,7 +687,7 @@ pub fn list_sort_with<'a, 'ctx, 'env>(
     )
 }
 
-/// List.mapWithIndex : List before, (Nat, before -> after) -> List after
+/// List.mapWithIndex : List before, (before, Nat -> after) -> List after
 pub fn list_map_with_index<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
     roc_function_call: RocFunctionCall<'ctx>,

compiler/test_gen/src/gen_list.rs

@@ -2363,7 +2363,7 @@ fn list_keep_errs() {
 #[cfg(any(feature = "gen-llvm"))]
 fn list_map_with_index() {
     assert_evals_to!(
-        "List.mapWithIndex [0,0,0] (\\index, x -> Num.intCast index + x)",
+        "List.mapWithIndex [0,0,0] (\\x, index -> Num.intCast index + x)",
         RocList::from_slice(&[0, 1, 2]),
         RocList<i64>
     );

examples/cli/echo.roc

@@ -23,7 +23,7 @@ echo = \shout ->
     shout
         |> Str.toUtf8
         |> List.mapWithIndex
-        (\i, _ ->
+        (\_, i ->
                 length = (List.len (Str.toUtf8 shout) - i)
                 phrase = (List.split (Str.toUtf8 shout) length).before