diff --git a/ast/src/solve_type.rs b/ast/src/solve_type.rs
index 2b39c606b3..ce63419a56 100644
--- a/ast/src/solve_type.rs
+++ b/ast/src/solve_type.rs
@@ -810,17 +810,13 @@ fn type_to_variable<'a>(
             */
 
             let mut arg_vars = Vec::with_capacity(args.len());
-            let mut new_aliases = BumpMap::new_in(arena);
 
-            for (arg, arg_type_id) in args.iter(mempool) {
+            for (_, arg_type_id) in args.iter(mempool) {
                 let arg_type = mempool.get(*arg_type_id);
 
                 let arg_var = type_to_variable(arena, mempool, subs, rank, pools, cached, arg_type);
 
-                let arg_str = arg.as_str(mempool);
-
-                arg_vars.push((roc_module::ident::Lowercase::from(arg_str), arg_var));
-                new_aliases.insert(arg_str, arg_var);
+                arg_vars.push(arg_var);
             }
 
             let arg_vars = AliasVariables::insert_into_subs(subs, arg_vars, []);
diff --git a/compiler/module/src/ident.rs b/compiler/module/src/ident.rs
index 6f31a28751..57e3c7f18c 100644
--- a/compiler/module/src/ident.rs
+++ b/compiler/module/src/ident.rs
@@ -29,7 +29,7 @@ impl std::ops::Deref for ModuleName {
 }
 
 /// An uncapitalized identifier, such as a field name or local variable
-#[derive(Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
+#[derive(Clone, Default, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct Lowercase(IdentStr);
 
 /// A capitalized identifier, such as a tag name or module name
diff --git a/compiler/solve/src/solve.rs b/compiler/solve/src/solve.rs
index f7741fcb4a..59fe4f868d 100644
--- a/compiler/solve/src/solve.rs
+++ b/compiler/solve/src/solve.rs
@@ -100,15 +100,17 @@ impl Pools {
     }
 
     pub fn get_mut(&mut self, rank: Rank) -> &mut Vec<Variable> {
-        self.0
-            .get_mut(rank.into_usize())
-            .unwrap_or_else(|| panic!("Compiler bug: could not find pool at rank {}", rank))
+        match self.0.get_mut(rank.into_usize()) {
+            Some(reference) => reference,
+            None => panic!("Compiler bug: could not find pool at rank {}", rank),
+        }
     }
 
     pub fn get(&self, rank: Rank) -> &Vec<Variable> {
-        self.0
-            .get(rank.into_usize())
-            .unwrap_or_else(|| panic!("Compiler bug: could not find pool at rank {}", rank))
+        match self.0.get(rank.into_usize()) {
+            Some(reference) => reference,
+            None => panic!("Compiler bug: could not find pool at rank {}", rank),
+        }
     }
 
     pub fn iter(&self) -> std::slice::Iter<'_, Vec<Variable>> {
@@ -628,18 +630,6 @@ fn type_to_var(
     type_to_variable(subs, rank, pools, &arena, typ)
 }
 
-/// Abusing existing functions for our purposes
-/// this is to put a solved type back into subs
-pub fn insert_type_into_subs(subs: &mut Subs, typ: &Type) -> Variable {
-    let rank = Rank::NONE;
-    let mut pools = Pools::default();
-
-    // capacity based on the false hello world program
-    let arena = bumpalo::Bump::with_capacity(4 * 1024);
-
-    type_to_variable(subs, rank, &mut pools, &arena, typ)
-}
-
 fn type_to_variable<'a>(
     subs: &mut Subs,
     rank: Rank,
@@ -652,14 +642,13 @@ fn type_to_variable<'a>(
     match typ {
         Variable(var) => *var,
         Apply(symbol, args) => {
-            let mut new_arg_vars = Vec::with_capacity_in(args.len(), arena);
+            let arg_vars = VariableSubsSlice::reserve_into_subs(subs, args.len());
 
-            for arg in args {
+            for (i, arg) in (arg_vars.slice.start as usize..).zip(args) {
                 let var = type_to_variable(subs, rank, pools, arena, arg);
-                new_arg_vars.push(var);
+                subs.variables[i] = var;
             }
 
-            let arg_vars = VariableSubsSlice::insert_into_subs(subs, new_arg_vars);
             let flat_type = FlatType::Apply(*symbol, arg_vars);
             let content = Content::Structure(flat_type);
 
@@ -669,16 +658,14 @@ fn type_to_variable<'a>(
         EmptyTagUnion => Variable::EMPTY_TAG_UNION,
 
         // This case is important for the rank of boolean variables
-        Function(arg_vars, closure_type, ret_type) => {
-            let mut new_arg_vars = Vec::with_capacity_in(arg_vars.len(), arena);
+        Function(args, closure_type, ret_type) => {
+            let arg_vars = VariableSubsSlice::reserve_into_subs(subs, args.len());
 
-            for arg in arg_vars {
+            for (i, arg) in (arg_vars.slice.start as usize..).zip(args) {
                 let var = type_to_variable(subs, rank, pools, arena, arg);
-                new_arg_vars.push(var);
+                subs.variables[i] = var;
             }
 
-            let arg_vars = VariableSubsSlice::insert_into_subs(subs, new_arg_vars);
-
             let ret_var = type_to_variable(subs, rank, pools, arena, ret_type);
             let closure_var = type_to_variable(subs, rank, pools, arena, closure_type);
             let content = Content::Structure(FlatType::Func(arg_vars, closure_var, ret_var));
@@ -801,10 +788,10 @@ fn type_to_variable<'a>(
 
             let mut arg_vars = Vec::with_capacity_in(args.len(), arena);
 
-            for (arg, arg_type) in args {
+            for (_, arg_type) in args {
                 let arg_var = type_to_variable(subs, rank, pools, arena, arg_type);
 
-                arg_vars.push((arg.clone(), arg_var));
+                arg_vars.push(arg_var);
             }
 
             let lambda_set_variables_it = lambda_set_variables
@@ -829,10 +816,10 @@ fn type_to_variable<'a>(
         } => {
             let mut arg_vars = Vec::with_capacity_in(args.len(), arena);
 
-            for (arg, arg_type) in args {
+            for (_, arg_type) in args {
                 let arg_var = type_to_variable(subs, rank, pools, arena, arg_type);
 
-                arg_vars.push((arg.clone(), arg_var));
+                arg_vars.push(arg_var);
             }
 
             let lambda_set_variables_it = lambda_set_variables
@@ -884,14 +871,13 @@ fn type_to_union_tags<'a>(
 
     let mut tag_vars = Vec::with_capacity_in(tags.len(), arena);
 
-    let mut tag_argument_vars = Vec::with_capacity_in(tags.len(), arena);
     for (tag, tag_argument_types) in tags {
-        for arg_type in tag_argument_types {
-            let new_var = type_to_variable(subs, rank, pools, arena, arg_type);
-            tag_argument_vars.push(new_var);
-        }
+        let new_slice = VariableSubsSlice::reserve_into_subs(subs, tag_argument_types.len());
 
-        let new_slice = VariableSubsSlice::insert_into_subs(subs, tag_argument_vars.drain(..));
+        for (i, arg) in (new_slice.slice.start as usize..).zip(tag_argument_types) {
+            let var = type_to_variable(subs, rank, pools, arena, arg);
+            subs.variables[i] = var;
+        }
 
         tag_vars.push((tag.clone(), new_slice));
     }
@@ -1654,12 +1640,14 @@ fn deep_copy_var_help(
 }
 
 fn register(subs: &mut Subs, rank: Rank, pools: &mut Pools, content: Content) -> Variable {
-    let var = subs.fresh(Descriptor {
+    let descriptor = Descriptor {
         content,
         rank,
         mark: Mark::NONE,
         copy: OptVariable::NONE,
-    });
+    };
+
+    let var = subs.fresh(descriptor);
 
     pools.get_mut(rank).push(var);
 
diff --git a/compiler/types/src/pretty_print.rs b/compiler/types/src/pretty_print.rs
index 23576b9af3..dbfed01a18 100644
--- a/compiler/types/src/pretty_print.rs
+++ b/compiler/types/src/pretty_print.rs
@@ -199,7 +199,7 @@ fn find_names_needed(
         }
         Alias(_symbol, args, _actual) => {
             // only find names for named parameters!
-            for var_index in args.variables().into_iter().take(args.len()) {
+            for var_index in args.into_iter().take(args.len()) {
                 let var = subs[var_index];
                 find_names_needed(var, subs, roots, root_appearances, names_taken);
             }
@@ -309,7 +309,6 @@ fn write_content(env: &Env, content: &Content, subs: &Subs, buf: &mut String, pa
                     debug_assert_eq!(args.len(), 1);
 
                     let arg_var_index = args
-                        .variables()
                         .into_iter()
                         .next()
                         .expect("Num was not applied to a type argument!");
@@ -337,7 +336,7 @@ fn write_content(env: &Env, content: &Content, subs: &Subs, buf: &mut String, pa
                 _ => write_parens!(write_parens, buf, {
                     write_symbol(env, *symbol, buf);
 
-                    for var_index in args.variables() {
+                    for var_index in args.into_iter() {
                         let var = subs[var_index];
                         buf.push(' ');
                         write_content(
diff --git a/compiler/types/src/solved_types.rs b/compiler/types/src/solved_types.rs
index 5173dc43af..2473597a35 100644
--- a/compiler/types/src/solved_types.rs
+++ b/compiler/types/src/solved_types.rs
@@ -229,7 +229,7 @@ impl SolvedType {
         }
     }
 
-    pub fn from_var(subs: &Subs, var: Variable) -> Self {
+    fn from_var(subs: &Subs, var: Variable) -> Self {
         let mut seen = RecursionVars::default();
         Self::from_var_help(subs, &mut seen, var)
     }
@@ -254,16 +254,17 @@ impl SolvedType {
             Alias(symbol, args, actual_var) => {
                 let mut new_args = Vec::with_capacity(args.len());
 
-                for (name_index, var_index) in args.named_type_arguments() {
+                for var_index in args.named_type_arguments() {
                     let arg_var = subs[var_index];
 
-                    new_args.push((
-                        subs[name_index].clone(),
-                        Self::from_var_help(subs, recursion_vars, arg_var),
-                    ));
+                    let node = Self::from_var_help(subs, recursion_vars, arg_var);
+
+                    // NOTE we fake the lowercase here: the user will never get to see it anyway
+                    new_args.push((Lowercase::default(), node));
                 }
 
                 let mut solved_lambda_sets = Vec::with_capacity(0);
+
                 for var_index in args.unnamed_type_arguments() {
                     let var = subs[var_index];
 
diff --git a/compiler/types/src/subs.rs b/compiler/types/src/subs.rs
index 1ee1bcfc0e..abceb92e63 100644
--- a/compiler/types/src/subs.rs
+++ b/compiler/types/src/subs.rs
@@ -797,7 +797,7 @@ fn integer_type(
         Content::Structure(FlatType::TagUnion(tags, Variable::EMPTY_TAG_UNION))
     });
 
-    let vars = AliasVariables::insert_into_subs(subs, [("range".into(), signed64)], []);
+    let vars = AliasVariables::insert_into_subs(subs, [signed64], []);
     subs.set_content(num_integer_signed64, {
         Content::Alias(Symbol::NUM_INTEGER, vars, at_signed64)
     });
@@ -812,7 +812,7 @@ fn integer_type(
         Content::Structure(FlatType::TagUnion(tags, Variable::EMPTY_TAG_UNION))
     });
 
-    let vars = AliasVariables::insert_into_subs(subs, [("range".into(), integer_signed64)], []);
+    let vars = AliasVariables::insert_into_subs(subs, [integer_signed64], []);
     subs.set_content(num_integer_signed64, {
         Content::Alias(Symbol::NUM_NUM, vars, at_num_integer_signed64)
     });
@@ -1358,7 +1358,7 @@ impl From<Content> for Descriptor {
 static_assertions::assert_eq_size!([u8; 4 * 8], Content);
 static_assertions::assert_eq_size!([u8; 4 * 8], (Variable, Option<Lowercase>));
 static_assertions::assert_eq_size!([u8; 3 * 8], (Symbol, AliasVariables, Variable));
-static_assertions::assert_eq_size!([u8; 12], AliasVariables);
+static_assertions::assert_eq_size!([u8; 8], AliasVariables);
 static_assertions::assert_eq_size!([u8; 3 * 8], FlatType);
 
 #[derive(Clone, Debug)]
@@ -1382,29 +1382,26 @@ pub enum Content {
 
 #[derive(Clone, Copy, Debug, Default)]
 pub struct AliasVariables {
-    pub lowercases_start: u32,
     pub variables_start: u32,
-    pub lowercases_len: u16,
-    pub variables_len: u16,
+    pub all_variables_len: u16,
+
+    /// an alias has type variables and lambda set variables
+    pub type_variables_len: u16,
 }
 
 impl AliasVariables {
-    pub const fn names(&self) -> SubsSlice<Lowercase> {
-        SubsSlice::new(self.lowercases_start, self.lowercases_len)
-    }
-
     pub const fn variables(&self) -> VariableSubsSlice {
         VariableSubsSlice {
-            slice: SubsSlice::new(self.variables_start, self.variables_len),
+            slice: SubsSlice::new(self.variables_start, self.all_variables_len),
         }
     }
 
     pub const fn len(&self) -> usize {
-        self.lowercases_len as usize
+        self.type_variables_len as usize
     }
 
     pub const fn is_empty(&self) -> bool {
-        self.lowercases_len == 0
+        self.type_variables_len == 0
     }
 
     pub fn replace_variables(
@@ -1416,24 +1413,21 @@ impl AliasVariables {
         subs.variables.extend(variables);
         let variables_len = (subs.variables.len() - variables_start as usize) as u16;
 
-        debug_assert_eq!(variables_len, self.variables_len);
+        debug_assert_eq!(variables_len, self.all_variables_len);
 
         self.variables_start = variables_start;
     }
 
-    pub fn named_type_arguments(
-        &self,
-    ) -> impl Iterator<Item = (SubsIndex<Lowercase>, SubsIndex<Variable>)> {
-        let names = self.names();
-        let vars = self.variables();
-
-        names.into_iter().zip(vars.into_iter())
+    pub fn named_type_arguments(&self) -> impl Iterator<Item = SubsIndex<Variable>> {
+        self.variables()
+            .into_iter()
+            .take(self.type_variables_len as usize)
     }
 
     pub fn unnamed_type_arguments(&self) -> impl Iterator<Item = SubsIndex<Variable>> {
         self.variables()
             .into_iter()
-            .skip(self.lowercases_len as usize)
+            .skip(self.type_variables_len as usize)
     }
 
     pub fn insert_into_subs<I1, I2>(
@@ -1442,38 +1436,41 @@ impl AliasVariables {
         unnamed_arguments: I2,
     ) -> Self
     where
-        I1: IntoIterator<Item = (Lowercase, Variable)>,
+        I1: IntoIterator<Item = Variable>,
         I2: IntoIterator<Item = Variable>,
     {
-        let lowercases_start = subs.field_names.len() as u32;
         let variables_start = subs.variables.len() as u32;
 
-        let it1 = type_arguments.into_iter();
-        let it2 = unnamed_arguments.into_iter();
+        subs.variables.extend(type_arguments);
 
-        subs.variables
-            .reserve(it1.size_hint().0 + it2.size_hint().0);
-        subs.field_names.reserve(it1.size_hint().0);
+        let type_variables_len = (subs.variables.len() as u32 - variables_start) as u16;
 
-        for (field_name, var) in it1 {
-            subs.field_names.push(field_name);
-            subs.variables.push(var);
+        subs.variables.extend(unnamed_arguments);
+
+        let all_variables_len = (subs.variables.len() as u32 - variables_start) as u16;
+
+        if type_variables_len == 3 {
+            panic!();
         }
 
-        subs.variables.extend(it2);
-
-        let lowercases_len = (subs.field_names.len() as u32 - lowercases_start) as u16;
-        let variables_len = (subs.variables.len() as u32 - variables_start) as u16;
-
         Self {
-            lowercases_start,
             variables_start,
-            lowercases_len,
-            variables_len,
+            type_variables_len,
+            all_variables_len,
         }
     }
 }
 
+impl IntoIterator for AliasVariables {
+    type Item = <VariableSubsSlice as IntoIterator>::Item;
+
+    type IntoIter = <VariableSubsSlice as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.variables().into_iter()
+    }
+}
+
 impl Content {
     #[inline(always)]
     pub fn is_number(&self) -> bool {
@@ -1548,6 +1545,15 @@ impl VariableSubsSlice {
         }
     }
 
+    pub fn reserve_into_subs(subs: &mut Subs, length: usize) -> Self {
+        let start = subs.variables.len() as u32;
+
+        subs.variables
+            .extend(std::iter::repeat(Variable::NULL).take(length));
+
+        Self::new(start, length as u16)
+    }
+
     pub fn insert_into_subs<I>(subs: &mut Subs, input: I) -> Self
     where
         I: IntoIterator<Item = Variable>,
@@ -2081,7 +2087,7 @@ fn occurs(
                 let mut new_seen = seen.clone();
                 new_seen.insert(root_var);
 
-                for var_index in args.variables().into_iter() {
+                for var_index in args.into_iter() {
                     let var = subs[var_index];
                     short_circuit_help(subs, root_var, &new_seen, var)?;
                 }
@@ -2265,7 +2271,7 @@ fn explicit_substitute(
                     in_var
                 }
                 Alias(symbol, args, actual) => {
-                    for index in args.variables().into_iter() {
+                    for index in args.into_iter() {
                         let var = subs[index];
                         let new_var = explicit_substitute(subs, from, to, var, seen);
                         subs[index] = new_var;
@@ -2322,12 +2328,9 @@ fn get_var_names(
 
             RigidVar(name) => add_name(subs, 0, name, var, RigidVar, taken_names),
 
-            Alias(_, args, _) => args
-                .variables()
-                .into_iter()
-                .fold(taken_names, |answer, arg_var| {
-                    get_var_names(subs, subs[arg_var], answer)
-                }),
+            Alias(_, args, _) => args.into_iter().fold(taken_names, |answer, arg_var| {
+                get_var_names(subs, subs[arg_var], answer)
+            }),
 
             Structure(flat_type) => match flat_type {
                 FlatType::Apply(_, args) => {
@@ -2528,15 +2531,14 @@ fn content_to_err_type(
         Alias(symbol, args, aliased_to) => {
             let err_type = var_to_err_type(subs, state, aliased_to);
 
-            let mut err_args = Vec::with_capacity(args.names().len());
+            let mut err_args = Vec::with_capacity(args.len());
 
-            for (name_index, var_index) in args.named_type_arguments() {
-                let name = subs[name_index].clone();
+            for var_index in args.into_iter() {
                 let var = subs[var_index];
 
                 let arg = var_to_err_type(subs, state, var);
 
-                err_args.push((name, arg));
+                err_args.push(arg);
             }
 
             ErrorType::Alias(symbol, err_args, Box::new(err_type))
@@ -2989,7 +2991,6 @@ impl StorageSubs {
         offsets: &StorageSubsOffsets,
         mut alias_variables: AliasVariables,
     ) -> AliasVariables {
-        alias_variables.lowercases_start += offsets.field_names;
         alias_variables.variables_start += offsets.variables;
 
         alias_variables
@@ -3357,9 +3358,9 @@ fn deep_copy_var_to_help<'a>(
         }
 
         Alias(symbol, mut args, real_type_var) => {
-            let mut new_vars = Vec::with_capacity_in(args.variables().len(), arena);
+            let mut new_vars = Vec::with_capacity_in(args.len(), arena);
 
-            for var_index in args.variables() {
+            for var_index in args.into_iter() {
                 let var = source[var_index];
                 let new_var = deep_copy_var_to_help(arena, visited, source, target, max_rank, var);
 
@@ -3368,12 +3369,6 @@ fn deep_copy_var_to_help<'a>(
 
             args.replace_variables(target, new_vars);
 
-            let lowercases = &source.field_names[args.lowercases_start as usize..]
-                [..args.lowercases_len as usize];
-
-            args.lowercases_start = target.field_names.len() as u32;
-            target.field_names.extend(lowercases.iter().cloned());
-
             let new_real_type_var =
                 deep_copy_var_to_help(arena, visited, source, target, max_rank, real_type_var);
             let new_content = Alias(symbol, args, new_real_type_var);
diff --git a/compiler/types/src/types.rs b/compiler/types/src/types.rs
index 174b49e438..96e0190a43 100644
--- a/compiler/types/src/types.rs
+++ b/compiler/types/src/types.rs
@@ -1241,7 +1241,7 @@ pub enum ErrorType {
     TagUnion(SendMap<TagName, Vec<ErrorType>>, TypeExt),
     RecursiveTagUnion(Box<ErrorType>, SendMap<TagName, Vec<ErrorType>>, TypeExt),
     Function(Vec<ErrorType>, Box<ErrorType>, Box<ErrorType>),
-    Alias(Symbol, Vec<(Lowercase, ErrorType)>, Box<ErrorType>),
+    Alias(Symbol, Vec<ErrorType>, Box<ErrorType>),
     Error,
 }
 
@@ -1303,7 +1303,7 @@ fn write_error_type_help(
         Alias(Symbol::NUM_NUM, mut arguments, _actual) => {
             debug_assert!(arguments.len() == 1);
 
-            let argument = arguments.remove(0).1;
+            let argument = arguments.remove(0);
 
             match argument {
                 Type(Symbol::NUM_INTEGER, _) => {
@@ -1421,7 +1421,7 @@ fn write_debug_error_type_help(error_type: ErrorType, buf: &mut String, parens:
         Alias(Symbol::NUM_NUM, mut arguments, _actual) => {
             debug_assert!(arguments.len() == 1);
 
-            let argument = arguments.remove(0).1;
+            let argument = arguments.remove(0);
 
             match argument {
                 Type(Symbol::NUM_INTEGER, _) => {
@@ -1456,7 +1456,7 @@ fn write_debug_error_type_help(error_type: ErrorType, buf: &mut String, parens:
             for arg in arguments {
                 buf.push(' ');
 
-                write_debug_error_type_help(arg.1, buf, Parens::InTypeParam);
+                write_debug_error_type_help(arg, buf, Parens::InTypeParam);
             }
 
             // useful for debugging
diff --git a/compiler/unify/src/unify.rs b/compiler/unify/src/unify.rs
index f469b0be1c..ff8f51966e 100644
--- a/compiler/unify/src/unify.rs
+++ b/compiler/unify/src/unify.rs
@@ -209,7 +209,8 @@ fn unify_alias(
 
                     problems
                 } else {
-                    mismatch!("{}", symbol)
+                    dbg!(args.len(), other_args.len());
+                    mismatch!("{:?}", symbol)
                 }
             } else {
                 unify_pool(subs, pool, real_var, *other_real_var)
diff --git a/editor/src/editor/main.rs b/editor/src/editor/main.rs
index cc27fb2848..e94412d628 100644
--- a/editor/src/editor/main.rs
+++ b/editor/src/editor/main.rs
@@ -471,12 +471,7 @@ fn read_main_roc_file(project_dir_path_opt: Option<&Path>) -> (PathStr, String)
         let project_dir_path_str = path_to_string(project_dir_path);
 
         if let Some(&roc_file_name) = roc_file_names.first() {
-            let full_roc_file_path_str = vec![
-                project_dir_path_str.clone(),
-                "/".to_owned(),
-                roc_file_name.clone(),
-            ]
-            .join("");
+            let full_roc_file_path_str = path_to_string(&project_dir_path.join(roc_file_name));
             let file_as_str = std::fs::read_to_string(&Path::new(&full_roc_file_path_str))
                 .unwrap_or_else(|err| panic!("In the provided project {:?}, I found the roc file {}, but I failed to read it: {}", &project_dir_path_str, &full_roc_file_path_str, err));
 
diff --git a/reporting/src/error/type.rs b/reporting/src/error/type.rs
index f80f3b63c9..d8745a1a9c 100644
--- a/reporting/src/error/type.rs
+++ b/reporting/src/error/type.rs
@@ -1493,7 +1493,7 @@ pub fn to_doc<'b>(
             parens,
             alloc.symbol_foreign_qualified(symbol),
             args.into_iter()
-                .map(|(_, arg)| to_doc(alloc, Parens::InTypeParam, arg))
+                .map(|arg| to_doc(alloc, Parens::InTypeParam, arg))
                 .collect(),
         ),
 
@@ -1657,10 +1657,7 @@ fn to_diff<'b>(
         }
 
         (Alias(symbol1, args1, _), Alias(symbol2, args2, _)) if symbol1 == symbol2 => {
-            // TODO remove collects
-            let a1 = args1.into_iter().map(|(_, v)| v).collect::<Vec<_>>();
-            let a2 = args2.into_iter().map(|(_, v)| v).collect::<Vec<_>>();
-            let args_diff = traverse(alloc, Parens::InTypeParam, a1, a2);
+            let args_diff = traverse(alloc, Parens::InTypeParam, args1, args2);
             let left = report_text::apply(
                 alloc,
                 parens,
@@ -1729,8 +1726,8 @@ fn to_diff<'b>(
                 ErrorType::Alias(Symbol::NUM_NUM, args, _) => {
                     matches!(
                         &args.get(0),
-                        Some((_, ErrorType::Type(Symbol::NUM_INTEGER, _)))
-                            | Some((_, ErrorType::Alias(Symbol::NUM_INTEGER, _, _)))
+                        Some(ErrorType::Type(Symbol::NUM_INTEGER, _))
+                            | Some(ErrorType::Alias(Symbol::NUM_INTEGER, _, _))
                     )
                 }
                 _ => false,
@@ -1750,8 +1747,8 @@ fn to_diff<'b>(
                 ErrorType::Alias(Symbol::NUM_NUM, args, _) => {
                     matches!(
                         &args.get(0),
-                        Some((_, ErrorType::Type(Symbol::NUM_FLOATINGPOINT, _)))
-                            | Some((_, ErrorType::Alias(Symbol::NUM_FLOATINGPOINT, _, _)))
+                        Some(ErrorType::Type(Symbol::NUM_FLOATINGPOINT, _))
+                            | Some(ErrorType::Alias(Symbol::NUM_FLOATINGPOINT, _, _))
                     )
                 }
                 _ => false,