diff --git a/.github/workflows/windows_release_build.yml b/.github/workflows/windows_release_build.yml
index b095c1205b..5fa53533e4 100644
--- a/.github/workflows/windows_release_build.yml
+++ b/.github/workflows/windows_release_build.yml
@@ -32,8 +32,8 @@ jobs:
       - name: zig version
         run: zig version
 
-      - name: install rust nightly 1.65
-        run: rustup install nightly-2022-09-17
+      - name: install rust nightly 1.68
+        run: rustup install nightly-2023-01-22
 
       - name: set up llvm 13
         run: |
diff --git a/.github/workflows/windows_tests.yml b/.github/workflows/windows_tests.yml
index 3388162109..3abb55781d 100644
--- a/.github/workflows/windows_tests.yml
+++ b/.github/workflows/windows_tests.yml
@@ -36,8 +36,8 @@ jobs:
       - name: zig version
         run: zig version
 
-      - name: install rust nightly 1.65
-        run: rustup install nightly-2022-09-17
+      - name: install rust nightly 1.68
+        run: rustup install nightly-2023-01-22
 
       - name: set up llvm 13
         run: |
diff --git a/crates/compiler/build/src/link.rs b/crates/compiler/build/src/link.rs
index 3cfad4a100..6210f8790a 100644
--- a/crates/compiler/build/src/link.rs
+++ b/crates/compiler/build/src/link.rs
@@ -629,7 +629,7 @@ pub fn rebuild_host(
             // on windows, we need the nightly toolchain so we can use `-Z export-executable-symbols`
             // using `+nightly` only works when running cargo through rustup
             let mut cmd = rustup();
-            cmd.args(["run", "nightly-2022-09-17", "cargo"]);
+            cmd.args(["run", "nightly-2023-01-22", "cargo"]);
 
             cmd
         } else {
diff --git a/crates/compiler/can/src/annotation.rs b/crates/compiler/can/src/annotation.rs
index 473fcdbc24..e80033c1e3 100644
--- a/crates/compiler/can/src/annotation.rs
+++ b/crates/compiler/can/src/annotation.rs
@@ -1134,7 +1134,7 @@ fn canonicalize_has_clause(
 }
 
 #[allow(clippy::too_many_arguments)]
-fn can_extension_type<'a>(
+fn can_extension_type(
     env: &mut Env,
     pol: CanPolarity,
     scope: &mut Scope,
@@ -1142,7 +1142,7 @@ fn can_extension_type<'a>(
     introduced_variables: &mut IntroducedVariables,
     local_aliases: &mut VecMap<Symbol, Alias>,
     references: &mut VecSet<Symbol>,
-    opt_ext: &Option<&Loc<TypeAnnotation<'a>>>,
+    opt_ext: &Option<&Loc<TypeAnnotation>>,
     ext_problem_kind: roc_problem::can::ExtensionTypeKind,
 ) -> (Type, ExtImplicitOpenness) {
     fn valid_record_ext_type(typ: &Type) -> bool {
@@ -1451,10 +1451,10 @@ fn can_assigned_fields<'a>(
 
 // TODO trim down these arguments!
 #[allow(clippy::too_many_arguments)]
-fn can_assigned_tuple_elems<'a>(
+fn can_assigned_tuple_elems(
     env: &mut Env,
     pol: CanPolarity,
-    elems: &&[Loc<TypeAnnotation<'a>>],
+    elems: &&[Loc<TypeAnnotation>],
     scope: &mut Scope,
     var_store: &mut VarStore,
     introduced_variables: &mut IntroducedVariables,
diff --git a/crates/compiler/can/src/def.rs b/crates/compiler/can/src/def.rs
index ee0879f180..426d5aa5e1 100644
--- a/crates/compiler/can/src/def.rs
+++ b/crates/compiler/can/src/def.rs
@@ -1051,7 +1051,6 @@ fn canonicalize_value_defs<'a>(
 
     for (def_index, pending_def) in pending_value_defs.iter().enumerate() {
         let mut new_bindings = BindingsFromPattern::new(pending_def.loc_pattern())
-            .into_iter()
             .peekable();
 
         if new_bindings.peek().is_none() {
@@ -1339,8 +1338,8 @@ fn canonicalize_type_defs<'a>(
 
 /// Resolve all pending abilities, to add them to scope.
 #[allow(clippy::too_many_arguments)]
-fn resolve_abilities<'a>(
-    env: &mut Env<'a>,
+fn resolve_abilities(
+    env: &mut Env,
     output: &mut Output,
     var_store: &mut VarStore,
     scope: &mut Scope,
@@ -2813,8 +2812,8 @@ fn to_pending_value_def<'a>(
 }
 
 /// Make aliases recursive
-fn correct_mutual_recursive_type_alias<'a>(
-    env: &mut Env<'a>,
+fn correct_mutual_recursive_type_alias(
+    env: &mut Env,
     original_aliases: VecMap<Symbol, Alias>,
     var_store: &mut VarStore,
 ) -> VecMap<Symbol, Alias> {
@@ -3022,8 +3021,8 @@ fn correct_mutual_recursive_type_alias<'a>(
     unsafe { VecMap::zip(symbols_introduced, aliases) }
 }
 
-fn make_tag_union_of_alias_recursive<'a>(
-    env: &mut Env<'a>,
+fn make_tag_union_of_alias_recursive(
+    env: &mut Env,
     alias_name: Symbol,
     alias: &mut Alias,
     others: Vec<Symbol>,
@@ -3215,8 +3214,8 @@ fn make_tag_union_recursive_help<'a, 'b>(
     }
 }
 
-fn mark_cyclic_alias<'a>(
-    env: &mut Env<'a>,
+fn mark_cyclic_alias(
+    env: &mut Env,
     typ: &mut Type,
     symbol: Symbol,
     alias_kind: AliasKind,
diff --git a/crates/compiler/can/src/module.rs b/crates/compiler/can/src/module.rs
index 105c7b0950..01417483ac 100644
--- a/crates/compiler/can/src/module.rs
+++ b/crates/compiler/can/src/module.rs
@@ -195,11 +195,11 @@ enum GeneratedInfo {
 }
 
 impl GeneratedInfo {
-    fn from_header_type<'a>(
+    fn from_header_type(
         env: &mut Env,
         scope: &mut Scope,
         var_store: &mut VarStore,
-        header_type: &HeaderType<'a>,
+        header_type: &HeaderType,
     ) -> Self {
         match header_type {
             HeaderType::Hosted {
diff --git a/crates/compiler/can/src/pattern.rs b/crates/compiler/can/src/pattern.rs
index 195957969f..d881ad4257 100644
--- a/crates/compiler/can/src/pattern.rs
+++ b/crates/compiler/can/src/pattern.rs
@@ -321,8 +321,8 @@ pub fn canonicalize_def_header_pattern<'a>(
 #[derive(PartialEq, Eq, Clone, Copy)]
 pub struct PermitShadows(pub bool);
 
-fn canonicalize_pattern_symbol<'a>(
-    env: &mut Env<'a>,
+fn canonicalize_pattern_symbol(
+    env: &mut Env,
     scope: &mut Scope,
     output: &mut Output,
     region: Region,
diff --git a/crates/compiler/can/src/traverse.rs b/crates/compiler/can/src/traverse.rs
index e2c657fff8..c22096ea72 100644
--- a/crates/compiler/can/src/traverse.rs
+++ b/crates/compiler/can/src/traverse.rs
@@ -122,7 +122,7 @@ pub fn walk_decls<V: Visitor>(visitor: &mut V, decls: &Declarations) {
                     None => Pattern::Identifier(loc_symbol.value),
                 };
 
-                let function_def = &decls.function_bodies[function_index.index() as usize];
+                let function_def = &decls.function_bodies[function_index.index()];
 
                 DeclarationInfo::Function {
                     loc_symbol,
@@ -133,7 +133,7 @@ pub fn walk_decls<V: Visitor>(visitor: &mut V, decls: &Declarations) {
                 }
             }
             Destructure(destructure_index) => {
-                let destructure = &decls.destructs[destructure_index.index() as usize];
+                let destructure = &decls.destructs[destructure_index.index()];
                 let loc_pattern = &destructure.loc_pattern;
 
                 let loc_expr = &decls.expressions[index];
diff --git a/crates/compiler/constrain/src/expr.rs b/crates/compiler/constrain/src/expr.rs
index f1292387aa..5261cf009c 100644
--- a/crates/compiler/constrain/src/expr.rs
+++ b/crates/compiler/constrain/src/expr.rs
@@ -2600,7 +2600,7 @@ pub fn constrain_decls(
                     cycle_mark,
                 );
 
-                index += length as usize;
+                index += length;
             }
         }
 
diff --git a/crates/compiler/derive/src/encoding.rs b/crates/compiler/derive/src/encoding.rs
index 183d489db1..4073e960a9 100644
--- a/crates/compiler/derive/src/encoding.rs
+++ b/crates/compiler/derive/src/encoding.rs
@@ -55,7 +55,6 @@ pub(crate) fn derive_to_encoder(
             // Generalized tuple var so we can reuse this impl between many tuples:
             // if arity = n, this is (t1, ..., tn) for fresh t1, ..., tn.
             let flex_elems = (0..arity)
-                .into_iter()
                 .map(|idx| (idx as usize, env.subs.fresh_unnamed_flex_var()))
                 .collect::<Vec<_>>();
             let elems = TupleElems::insert_into_subs(env.subs, flex_elems);
diff --git a/crates/compiler/derive/src/hash.rs b/crates/compiler/derive/src/hash.rs
index 1f597f2dda..f01a28eac2 100644
--- a/crates/compiler/derive/src/hash.rs
+++ b/crates/compiler/derive/src/hash.rs
@@ -131,7 +131,6 @@ fn hash_tuple(env: &mut Env<'_>, fn_name: Symbol, arity: u32) -> (Variable, Expr
         // TODO: avoid an allocation here by pre-allocating the indices and variables `TupleElems`
         // will be instantiated with.
         let flex_elems: Vec<_> = (0..arity)
-            .into_iter()
             .map(|i| (i as usize, env.subs.fresh_unnamed_flex_var()))
             .collect();
         let elems = TupleElems::insert_into_subs(env.subs, flex_elems);
diff --git a/crates/compiler/fmt/src/annotation.rs b/crates/compiler/fmt/src/annotation.rs
index 1091b81458..23da7721af 100644
--- a/crates/compiler/fmt/src/annotation.rs
+++ b/crates/compiler/fmt/src/annotation.rs
@@ -65,15 +65,15 @@ impl Newlines {
 pub trait Formattable {
     fn is_multiline(&self) -> bool;
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
     );
 
-    fn format<'buf>(&self, buf: &mut Buf<'buf>, indent: u16) {
+    fn format(&self, buf: &mut Buf, indent: u16) {
         self.format_with_options(buf, Parens::NotNeeded, Newlines::No, indent);
     }
 }
@@ -87,9 +87,9 @@ where
         (*self).is_multiline()
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -97,7 +97,7 @@ where
         (*self).format_with_options(buf, parens, newlines, indent)
     }
 
-    fn format<'buf>(&self, buf: &mut Buf<'buf>, indent: u16) {
+    fn format(&self, buf: &mut Buf, indent: u16) {
         (*self).format(buf, indent)
     }
 }
@@ -120,9 +120,9 @@ where
         self.value.is_multiline()
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -131,7 +131,7 @@ where
             .format_with_options(buf, parens, newlines, indent)
     }
 
-    fn format<'buf>(&self, buf: &mut Buf<'buf>, indent: u16) {
+    fn format(&self, buf: &mut Buf, indent: u16) {
         self.value.format(buf, indent)
     }
 }
@@ -141,9 +141,9 @@ impl<'a> Formattable for UppercaseIdent<'a> {
         false
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         _indent: u16,
@@ -206,9 +206,9 @@ impl<'a> Formattable for TypeAnnotation<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -424,9 +424,9 @@ impl<'a> Formattable for AssignedField<'a, TypeAnnotation<'a>> {
         is_multiline_assigned_field_help(self)
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -441,9 +441,9 @@ impl<'a> Formattable for AssignedField<'a, Expr<'a>> {
         is_multiline_assigned_field_help(self)
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -466,9 +466,9 @@ fn is_multiline_assigned_field_help<T: Formattable>(afield: &AssignedField<'_, T
     }
 }
 
-fn format_assigned_field_help<'a, 'buf, T>(
-    zelf: &AssignedField<'a, T>,
-    buf: &mut Buf<'buf>,
+fn format_assigned_field_help< T>(
+    zelf: &AssignedField<T>,
+    buf: &mut Buf,
     indent: u16,
     separator_spaces: usize,
     is_multiline: bool,
@@ -545,9 +545,9 @@ impl<'a> Formattable for Tag<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
@@ -592,9 +592,9 @@ impl<'a> Formattable for HasClause<'a> {
         false
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -623,9 +623,9 @@ impl<'a> Formattable for HasImpls<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -662,9 +662,9 @@ impl<'a> Formattable for HasAbility<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -703,9 +703,9 @@ impl<'a> Formattable for HasAbilities<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
diff --git a/crates/compiler/fmt/src/def.rs b/crates/compiler/fmt/src/def.rs
index d45e37b733..58a214078a 100644
--- a/crates/compiler/fmt/src/def.rs
+++ b/crates/compiler/fmt/src/def.rs
@@ -15,9 +15,9 @@ impl<'a> Formattable for Defs<'a> {
         !self.tags.is_empty()
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
@@ -57,9 +57,9 @@ impl<'a> Formattable for TypeDef<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -171,9 +171,9 @@ impl<'a> Formattable for TypeHeader<'a> {
         self.vars.iter().any(|v| v.is_multiline())
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
@@ -205,9 +205,9 @@ impl<'a> Formattable for ValueDef<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -314,8 +314,8 @@ fn should_outdent(mut rhs: &TypeAnnotation) -> bool {
     }
 }
 
-fn fmt_dbg_in_def<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_dbg_in_def<'a>(
+    buf: &mut Buf,
     condition: &'a Loc<Expr<'a>>,
     is_multiline: bool,
     indent: u16,
@@ -335,8 +335,8 @@ fn fmt_dbg_in_def<'a, 'buf>(
     condition.format(buf, return_indent);
 }
 
-fn fmt_expect<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_expect<'a>(
+    buf: &mut Buf,
     condition: &'a Loc<Expr<'a>>,
     is_multiline: bool,
     indent: u16,
@@ -356,8 +356,8 @@ fn fmt_expect<'a, 'buf>(
     condition.format(buf, return_indent);
 }
 
-fn fmt_expect_fx<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_expect_fx<'a>(
+    buf: &mut Buf,
     condition: &'a Loc<Expr<'a>>,
     is_multiline: bool,
     indent: u16,
@@ -377,24 +377,24 @@ fn fmt_expect_fx<'a, 'buf>(
     condition.format(buf, return_indent);
 }
 
-pub fn fmt_value_def<'a, 'buf>(
-    buf: &mut Buf<'buf>,
-    def: &roc_parse::ast::ValueDef<'a>,
+pub fn fmt_value_def(
+    buf: &mut Buf,
+    def: &roc_parse::ast::ValueDef,
     indent: u16,
 ) {
     def.format(buf, indent);
 }
 
-pub fn fmt_type_def<'a, 'buf>(buf: &mut Buf<'buf>, def: &roc_parse::ast::TypeDef<'a>, indent: u16) {
+pub fn fmt_type_def(buf: &mut Buf, def: &roc_parse::ast::TypeDef, indent: u16) {
     def.format(buf, indent);
 }
 
-pub fn fmt_defs<'a, 'buf>(buf: &mut Buf<'buf>, defs: &Defs<'a>, indent: u16) {
+pub fn fmt_defs(buf: &mut Buf, defs: &Defs, indent: u16) {
     defs.format(buf, indent);
 }
 
-pub fn fmt_body<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+pub fn fmt_body<'a>(
+    buf: &mut Buf,
     pattern: &'a Pattern<'a>,
     body: &'a Expr<'a>,
     indent: u16,
@@ -462,9 +462,9 @@ impl<'a> Formattable for AbilityMember<'a> {
         self.name.value.is_multiline() || self.typ.is_multiline()
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
diff --git a/crates/compiler/fmt/src/expr.rs b/crates/compiler/fmt/src/expr.rs
index b644f185c0..9721aea3cc 100644
--- a/crates/compiler/fmt/src/expr.rs
+++ b/crates/compiler/fmt/src/expr.rs
@@ -103,9 +103,9 @@ impl<'a> Formattable for Expr<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -551,7 +551,7 @@ fn starts_with_newline(expr: &Expr) -> bool {
     }
 }
 
-fn format_str_segment<'a, 'buf>(seg: &StrSegment<'a>, buf: &mut Buf<'buf>, indent: u16) {
+fn format_str_segment(seg: &StrSegment, buf: &mut Buf, indent: u16) {
     use StrSegment::*;
 
     match seg {
@@ -614,7 +614,7 @@ fn push_op(buf: &mut Buf, op: BinOp) {
     }
 }
 
-pub fn fmt_str_literal<'buf>(buf: &mut Buf<'buf>, literal: StrLiteral, indent: u16) {
+pub fn fmt_str_literal(buf: &mut Buf, literal: StrLiteral, indent: u16) {
     use roc_parse::ast::StrLiteral::*;
 
     match literal {
@@ -673,8 +673,8 @@ pub fn fmt_str_literal<'buf>(buf: &mut Buf<'buf>, literal: StrLiteral, indent: u
     }
 }
 
-fn fmt_binops<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_binops<'a>(
+    buf: &mut Buf,
     lefts: &'a [(Loc<Expr<'a>>, Loc<BinOp>)],
     loc_right_side: &'a Loc<Expr<'a>>,
     part_of_multi_line_binops: bool,
@@ -704,9 +704,9 @@ fn fmt_binops<'a, 'buf>(
     loc_right_side.format_with_options(buf, Parens::InOperator, Newlines::Yes, indent);
 }
 
-fn format_spaces<'a, 'buf>(
-    buf: &mut Buf<'buf>,
-    spaces: &[CommentOrNewline<'a>],
+fn format_spaces(
+    buf: &mut Buf,
+    spaces: &[CommentOrNewline],
     newlines: Newlines,
     indent: u16,
 ) {
@@ -738,8 +738,8 @@ fn is_when_patterns_multiline(when_branch: &WhenBranch) -> bool {
     is_multiline_patterns
 }
 
-fn fmt_when<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_when<'a>(
+    buf: &mut Buf,
     loc_condition: &'a Loc<Expr<'a>>,
     branches: &[&'a WhenBranch<'a>],
     indent: u16,
@@ -920,8 +920,8 @@ fn fmt_when<'a, 'buf>(
     }
 }
 
-fn fmt_dbg<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_dbg<'a>(
+    buf: &mut Buf,
     condition: &'a Loc<Expr<'a>>,
     continuation: &'a Loc<Expr<'a>>,
     is_multiline: bool,
@@ -947,8 +947,8 @@ fn fmt_dbg<'a, 'buf>(
     continuation.format(buf, indent);
 }
 
-fn fmt_expect<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_expect<'a>(
+    buf: &mut Buf,
     condition: &'a Loc<Expr<'a>>,
     continuation: &'a Loc<Expr<'a>>,
     is_multiline: bool,
@@ -974,8 +974,8 @@ fn fmt_expect<'a, 'buf>(
     continuation.format(buf, indent);
 }
 
-fn fmt_if<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_if<'a>(
+    buf: &mut Buf,
     branches: &'a [(Loc<Expr<'a>>, Loc<Expr<'a>>)],
     final_else: &'a Loc<Expr<'a>>,
     is_multiline: bool,
@@ -1123,8 +1123,8 @@ fn fmt_if<'a, 'buf>(
     final_else.format(buf, return_indent);
 }
 
-fn fmt_closure<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_closure<'a>(
+    buf: &mut Buf,
     loc_patterns: &'a [Loc<Pattern<'a>>],
     loc_ret: &'a Loc<Expr<'a>>,
     indent: u16,
@@ -1224,8 +1224,8 @@ fn fmt_closure<'a, 'buf>(
     }
 }
 
-fn fmt_backpassing<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_backpassing<'a>(
+    buf: &mut Buf,
     loc_patterns: &'a [Loc<Pattern<'a>>],
     loc_body: &'a Loc<Expr<'a>>,
     loc_ret: &'a Loc<Expr<'a>>,
@@ -1312,8 +1312,8 @@ fn pattern_needs_parens_when_backpassing(pat: &Pattern) -> bool {
     }
 }
 
-fn fmt_record<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_record<'a>(
+    buf: &mut Buf,
     update: Option<&'a Loc<Expr<'a>>>,
     fields: Collection<'a, Loc<AssignedField<'a, Expr<'a>>>>,
     indent: u16,
@@ -1404,9 +1404,9 @@ fn fmt_record<'a, 'buf>(
     }
 }
 
-fn format_field_multiline<'a, 'buf, T>(
-    buf: &mut Buf<'buf>,
-    field: &AssignedField<'a, T>,
+fn format_field_multiline<T>(
+    buf: &mut Buf,
+    field: &AssignedField<T>,
     indent: u16,
     separator_prefix: &str,
 ) where
diff --git a/crates/compiler/fmt/src/module.rs b/crates/compiler/fmt/src/module.rs
index ab818b9ed0..e5e44884e6 100644
--- a/crates/compiler/fmt/src/module.rs
+++ b/crates/compiler/fmt/src/module.rs
@@ -86,9 +86,9 @@ impl<V: Formattable> Formattable for Option<V> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: crate::annotation::Parens,
         newlines: Newlines,
         indent: u16,
@@ -111,9 +111,9 @@ impl<'a> Formattable for ProvidesTo<'a> {
             || self.to_keyword.is_multiline()
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: crate::annotation::Parens,
         _newlines: Newlines,
         indent: u16,
@@ -130,9 +130,9 @@ impl<'a> Formattable for PlatformRequires<'a> {
         is_collection_multiline(&self.rigids) || self.signature.is_multiline()
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: crate::annotation::Parens,
         _newlines: Newlines,
         indent: u16,
@@ -146,9 +146,9 @@ impl<'a, V: Formattable> Formattable for Spaces<'a, V> {
         !self.before.is_empty() || !self.after.is_empty() || self.item.is_multiline()
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: crate::annotation::Parens,
         newlines: Newlines,
         indent: u16,
@@ -164,9 +164,9 @@ impl<'a, K: Formattable, V: Formattable> Formattable for KeywordItem<'a, K, V> {
         self.keyword.is_multiline() || self.item.is_multiline()
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
@@ -177,7 +177,7 @@ impl<'a, K: Formattable, V: Formattable> Formattable for KeywordItem<'a, K, V> {
     }
 }
 
-pub fn fmt_interface_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a InterfaceHeader<'a>) {
+pub fn fmt_interface_header<'a>(buf: &mut Buf, header: &'a InterfaceHeader<'a>) {
     buf.indent(0);
     buf.push_str("interface");
     let indent = INDENT;
@@ -193,7 +193,7 @@ pub fn fmt_interface_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a Interface
     fmt_imports(buf, header.imports.item, indent);
 }
 
-pub fn fmt_hosted_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a HostedHeader<'a>) {
+pub fn fmt_hosted_header<'a>(buf: &mut Buf, header: &'a HostedHeader<'a>) {
     buf.indent(0);
     buf.push_str("hosted");
     let indent = INDENT;
@@ -210,7 +210,7 @@ pub fn fmt_hosted_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a HostedHeader
     fmt_exposes(buf, header.generates_with.item, indent);
 }
 
-pub fn fmt_app_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a AppHeader<'a>) {
+pub fn fmt_app_header<'a>(buf: &mut Buf, header: &'a AppHeader<'a>) {
     buf.indent(0);
     buf.push_str("app");
     let indent = INDENT;
@@ -229,7 +229,7 @@ pub fn fmt_app_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a AppHeader<'a>)
     header.provides.format(buf, indent);
 }
 
-pub fn fmt_package_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a PackageHeader<'a>) {
+pub fn fmt_package_header<'a>(buf: &mut Buf, header: &'a PackageHeader<'a>) {
     buf.indent(0);
     buf.push_str("package");
     let indent = INDENT;
@@ -243,7 +243,7 @@ pub fn fmt_package_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a PackageHead
     fmt_packages(buf, header.packages.item, indent);
 }
 
-pub fn fmt_platform_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a PlatformHeader<'a>) {
+pub fn fmt_platform_header<'a>(buf: &mut Buf, header: &'a PlatformHeader<'a>) {
     buf.indent(0);
     buf.push_str("platform");
     let indent = INDENT;
@@ -262,7 +262,7 @@ pub fn fmt_platform_header<'a, 'buf>(buf: &mut Buf<'buf>, header: &'a PlatformHe
     fmt_provides(buf, header.provides.item, None, indent);
 }
 
-fn fmt_requires<'a, 'buf>(buf: &mut Buf<'buf>, requires: &PlatformRequires<'a>, indent: u16) {
+fn fmt_requires(buf: &mut Buf, requires: &PlatformRequires, indent: u16) {
     fmt_collection(buf, indent, Braces::Curly, requires.rigids, Newlines::No);
 
     buf.push_str(" {");
@@ -276,9 +276,9 @@ impl<'a> Formattable for TypedIdent<'a> {
         false
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
@@ -293,7 +293,7 @@ impl<'a> Formattable for TypedIdent<'a> {
     }
 }
 
-fn fmt_package_name<'buf>(buf: &mut Buf<'buf>, name: PackageName, indent: u16) {
+fn fmt_package_name(buf: &mut Buf, name: PackageName, indent: u16) {
     buf.indent(indent);
     buf.push('"');
     buf.push_str_allow_spaces(name.to_str());
@@ -312,9 +312,9 @@ impl<'a, T: Formattable> Formattable for Spaced<'a, T> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: crate::annotation::Parens,
         newlines: Newlines,
         indent: u16,
@@ -335,16 +335,16 @@ impl<'a, T: Formattable> Formattable for Spaced<'a, T> {
     }
 }
 
-fn fmt_imports<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_imports<'a>(
+    buf: &mut Buf,
     loc_entries: Collection<'a, Loc<Spaced<'a, ImportsEntry<'a>>>>,
     indent: u16,
 ) {
     fmt_collection(buf, indent, Braces::Square, loc_entries, Newlines::No)
 }
 
-fn fmt_provides<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_provides<'a>(
+    buf: &mut Buf,
     loc_exposed_names: Collection<'a, Loc<Spaced<'a, ExposedName<'a>>>>,
     loc_provided_types: Option<Collection<'a, Loc<Spaced<'a, UppercaseIdent<'a>>>>>,
     indent: u16,
@@ -356,7 +356,7 @@ fn fmt_provides<'a, 'buf>(
     }
 }
 
-fn fmt_to<'buf>(buf: &mut Buf<'buf>, to: To, indent: u16) {
+fn fmt_to(buf: &mut Buf, to: To, indent: u16) {
     match to {
         To::ExistingPackage(name) => {
             buf.push_str(name);
@@ -365,8 +365,8 @@ fn fmt_to<'buf>(buf: &mut Buf<'buf>, to: To, indent: u16) {
     }
 }
 
-fn fmt_exposes<'buf, N: Formattable + Copy + core::fmt::Debug>(
-    buf: &mut Buf<'buf>,
+fn fmt_exposes<N: Formattable + Copy + core::fmt::Debug>(
+    buf: &mut Buf,
     loc_entries: Collection<'_, Loc<Spaced<'_, N>>>,
     indent: u16,
 ) {
@@ -374,17 +374,17 @@ fn fmt_exposes<'buf, N: Formattable + Copy + core::fmt::Debug>(
 }
 
 pub trait FormatName {
-    fn format<'buf>(&self, buf: &mut Buf<'buf>);
+    fn format(&self, buf: &mut Buf);
 }
 
 impl<'a> FormatName for &'a str {
-    fn format<'buf>(&self, buf: &mut Buf<'buf>) {
+    fn format(&self, buf: &mut Buf) {
         buf.push_str(self)
     }
 }
 
 impl<'a> FormatName for ModuleName<'a> {
-    fn format<'buf>(&self, buf: &mut Buf<'buf>) {
+    fn format(&self, buf: &mut Buf) {
         buf.push_str(self.as_str());
     }
 }
@@ -394,9 +394,9 @@ impl<'a> Formattable for ModuleName<'a> {
         false
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         _indent: u16,
@@ -410,9 +410,9 @@ impl<'a> Formattable for ExposedName<'a> {
         false
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
@@ -423,13 +423,13 @@ impl<'a> Formattable for ExposedName<'a> {
 }
 
 impl<'a> FormatName for ExposedName<'a> {
-    fn format<'buf>(&self, buf: &mut Buf<'buf>) {
+    fn format(&self, buf: &mut Buf) {
         buf.push_str(self.as_str());
     }
 }
 
-fn fmt_packages<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+fn fmt_packages<'a>(
+    buf: &mut Buf,
     loc_entries: Collection<'a, Loc<Spaced<'a, PackageEntry<'a>>>>,
     indent: u16,
 ) {
@@ -441,9 +441,9 @@ impl<'a> Formattable for PackageEntry<'a> {
         false
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
@@ -457,9 +457,9 @@ impl<'a> Formattable for ImportsEntry<'a> {
         false
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
@@ -467,14 +467,14 @@ impl<'a> Formattable for ImportsEntry<'a> {
         fmt_imports_entry(buf, self, indent);
     }
 }
-fn fmt_packages_entry<'a, 'buf>(buf: &mut Buf<'buf>, entry: &PackageEntry<'a>, indent: u16) {
+fn fmt_packages_entry(buf: &mut Buf, entry: &PackageEntry, indent: u16) {
     buf.push_str(entry.shorthand);
     buf.push(':');
     fmt_default_spaces(buf, entry.spaces_after_shorthand, indent);
     fmt_package_name(buf, entry.package_name.value, indent);
 }
 
-fn fmt_imports_entry<'a, 'buf>(buf: &mut Buf<'buf>, entry: &ImportsEntry<'a>, indent: u16) {
+fn fmt_imports_entry(buf: &mut Buf, entry: &ImportsEntry, indent: u16) {
     use roc_parse::header::ImportsEntry::*;
 
     buf.indent(indent);
diff --git a/crates/compiler/fmt/src/pattern.rs b/crates/compiler/fmt/src/pattern.rs
index e1d4265569..3775b4cc35 100644
--- a/crates/compiler/fmt/src/pattern.rs
+++ b/crates/compiler/fmt/src/pattern.rs
@@ -4,8 +4,8 @@ use crate::spaces::{fmt_comments_only, fmt_spaces, NewlineAt, INDENT};
 use crate::Buf;
 use roc_parse::ast::{Base, CommentOrNewline, Pattern, PatternAs};
 
-pub fn fmt_pattern<'a, 'buf>(
-    buf: &mut Buf<'buf>,
+pub fn fmt_pattern<'a>(
+    buf: &mut Buf,
     pattern: &'a Pattern<'a>,
     indent: u16,
     parens: Parens,
@@ -18,9 +18,9 @@ impl<'a> Formattable for PatternAs<'a> {
         self.spaces_before.iter().any(|s| s.is_comment())
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         _parens: Parens,
         _newlines: Newlines,
         indent: u16,
@@ -85,9 +85,9 @@ impl<'a> Formattable for Pattern<'a> {
         }
     }
 
-    fn format_with_options<'buf>(
+    fn format_with_options(
         &self,
-        buf: &mut Buf<'buf>,
+        buf: &mut Buf,
         parens: Parens,
         newlines: Newlines,
         indent: u16,
diff --git a/crates/compiler/fmt/src/spaces.rs b/crates/compiler/fmt/src/spaces.rs
index 172b7c7d9f..35b921a822 100644
--- a/crates/compiler/fmt/src/spaces.rs
+++ b/crates/compiler/fmt/src/spaces.rs
@@ -21,9 +21,9 @@ use crate::{Ast, Buf};
 /// The number of spaces to indent.
 pub const INDENT: u16 = 4;
 
-pub fn fmt_default_spaces<'a, 'buf>(
-    buf: &mut Buf<'buf>,
-    spaces: &[CommentOrNewline<'a>],
+pub fn fmt_default_spaces(
+    buf: &mut Buf,
+    spaces: &[CommentOrNewline],
     indent: u16,
 ) {
     if spaces.is_empty() {
@@ -32,9 +32,9 @@ pub fn fmt_default_spaces<'a, 'buf>(
         fmt_spaces(buf, spaces.iter(), indent);
     }
 }
-pub fn fmt_default_newline<'a, 'buf>(
-    buf: &mut Buf<'buf>,
-    spaces: &[CommentOrNewline<'a>],
+pub fn fmt_default_newline(
+    buf: &mut Buf,
+    spaces: &[CommentOrNewline],
     indent: u16,
 ) {
     if spaces.is_empty() {
@@ -153,7 +153,7 @@ pub fn fmt_comments_only<'a, 'buf, I>(
     }
 }
 
-fn fmt_comment<'buf>(buf: &mut Buf<'buf>, comment: &str) {
+fn fmt_comment(buf: &mut Buf, comment: &str) {
     // The '#' in a comment should always be preceded by a newline or a space,
     // unless it's the very beginning of the buffer.
     if !buf.is_empty() && !buf.ends_with_space() && !buf.ends_with_newline() {
@@ -192,7 +192,7 @@ where
     count
 }
 
-fn fmt_docs<'buf>(buf: &mut Buf<'buf>, docs: &str) {
+fn fmt_docs(buf: &mut Buf, docs: &str) {
     // The "##" in a doc comment should always be preceded by a newline or a space,
     // unless it's the very beginning of the buffer.
     if !buf.is_empty() && !buf.ends_with_space() && !buf.ends_with_newline() {
diff --git a/crates/compiler/mono/src/inc_dec.rs b/crates/compiler/mono/src/inc_dec.rs
index e2b644ec00..75188b666f 100644
--- a/crates/compiler/mono/src/inc_dec.rs
+++ b/crates/compiler/mono/src/inc_dec.rs
@@ -25,9 +25,9 @@ use crate::{
 /**
 Insert the reference count operations for procedures.
 */
-pub fn insert_inc_dec_operations<'a, 'i>(
+pub fn insert_inc_dec_operations<'a>(
     arena: &'a Bump,
-    layout_interner: &'i STLayoutInterner<'a>,
+    layout_interner: &STLayoutInterner<'a>,
     procedures: &mut HashMap<(Symbol, ProcLayout), Proc<'a>, BuildHasherDefault<WyHash>>,
 ) {
     // Create a SymbolRcTypesEnv for the procedures as they get referenced but should be marked as non reference counted.
@@ -401,9 +401,9 @@ impl<'v> RefcountEnvironment<'v> {
 /**
  Insert the reference counting operations into a statement.
 */
-fn insert_inc_dec_operations_proc<'a, 'i>(
+fn insert_inc_dec_operations_proc<'a>(
     arena: &'a Bump,
-    mut symbol_rc_types_env: SymbolRcTypesEnv<'a, 'i>,
+    mut symbol_rc_types_env: SymbolRcTypesEnv<'a, '_>,
     proc: &mut Proc<'a>,
 ) {
     // Clone the symbol_rc_types_env and insert the symbols in the current procedure.
diff --git a/crates/compiler/mono/src/ir.rs b/crates/compiler/mono/src/ir.rs
index af41bb0ca0..cc6e5c16a7 100644
--- a/crates/compiler/mono/src/ir.rs
+++ b/crates/compiler/mono/src/ir.rs
@@ -72,8 +72,8 @@ roc_error_macros::assert_sizeof_wasm!(Call, 44);
 roc_error_macros::assert_sizeof_wasm!(CallType, 36);
 
 roc_error_macros::assert_sizeof_non_wasm!(Literal, 3 * 8);
-roc_error_macros::assert_sizeof_non_wasm!(Expr, 9 * 8);
-roc_error_macros::assert_sizeof_non_wasm!(Stmt, 12 * 8);
+roc_error_macros::assert_sizeof_non_wasm!(Expr, 10 * 8);
+roc_error_macros::assert_sizeof_non_wasm!(Stmt, 13 * 8);
 roc_error_macros::assert_sizeof_non_wasm!(ProcLayout, 5 * 8);
 roc_error_macros::assert_sizeof_non_wasm!(Call, 9 * 8);
 roc_error_macros::assert_sizeof_non_wasm!(CallType, 7 * 8);
@@ -279,8 +279,9 @@ impl AbilityAliases {
     }
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Default)]
 pub enum CapturedSymbols<'a> {
+    #[default]
     None,
     Captured(&'a [(Symbol, Variable)]),
 }
@@ -294,12 +295,6 @@ impl<'a> CapturedSymbols<'a> {
     }
 }
 
-impl<'a> Default for CapturedSymbols<'a> {
-    fn default() -> Self {
-        CapturedSymbols::None
-    }
-}
-
 #[derive(Clone, Debug, PartialEq)]
 pub struct Proc<'a> {
     pub name: LambdaName<'a>,
@@ -2722,8 +2717,8 @@ fn patterns_to_when<'a>(
 ///          { x } -> body
 ///
 /// conversion of one-pattern when expressions will do the most optimal thing
-fn pattern_to_when<'a>(
-    env: &mut Env<'a, '_>,
+fn pattern_to_when(
+    env: &mut Env<'_, '_>,
     pattern_var: Variable,
     pattern: Loc<roc_can::pattern::Pattern>,
     body_var: Variable,
@@ -5740,8 +5735,8 @@ fn compile_struct_like<'a, L, UnusedLayout>(
 }
 
 #[inline(always)]
-fn late_resolve_ability_specialization<'a>(
-    env: &mut Env<'a, '_>,
+fn late_resolve_ability_specialization(
+    env: &mut Env<'_, '_>,
     member: Symbol,
     specialization_id: Option<SpecializationId>,
     specialization_var: Variable,
diff --git a/crates/compiler/mono/src/ir/decision_tree.rs b/crates/compiler/mono/src/ir/decision_tree.rs
index c5c1a48425..d81fbae021 100644
--- a/crates/compiler/mono/src/ir/decision_tree.rs
+++ b/crates/compiler/mono/src/ir/decision_tree.rs
@@ -1193,7 +1193,7 @@ fn extract<'a>(
 
 /// FIND IRRELEVANT BRANCHES
 
-fn is_irrelevant_to<'a>(selected_path: &[PathInstruction], branch: &Branch<'a>) -> bool {
+fn is_irrelevant_to(selected_path: &[PathInstruction], branch: &Branch) -> bool {
     match branch
         .patterns
         .iter()
@@ -1720,7 +1720,7 @@ fn test_to_comparison<'a>(
 
         Test::IsFloat(test_int, precision) => {
             // TODO maybe we can actually use i64 comparison here?
-            let test_float = f64::from_bits(test_int as u64);
+            let test_float = f64::from_bits(test_int);
             let lhs = Expr::Literal(Literal::Float(test_float));
             let lhs_symbol = env.unique_symbol();
             stores.push((lhs_symbol, Layout::float_width(precision), lhs));
@@ -2240,7 +2240,7 @@ fn decide_to_branching<'a>(
 
                 let tag = match test {
                     Test::IsInt(v, _) => i128::from_ne_bytes(v) as u64,
-                    Test::IsFloat(v, _) => v as u64,
+                    Test::IsFloat(v, _) => v,
                     Test::IsBit(v) => v as u64,
                     Test::IsByte { tag_id, .. } => tag_id as u64,
                     Test::IsCtor { tag_id, .. } => tag_id as u64,
diff --git a/crates/compiler/mono/src/layout.rs b/crates/compiler/mono/src/layout.rs
index a90a275234..bcd07d254e 100644
--- a/crates/compiler/mono/src/layout.rs
+++ b/crates/compiler/mono/src/layout.rs
@@ -457,7 +457,7 @@ macro_rules! cached {
 }
 
 pub type TagIdIntType = u16;
-pub const MAX_ENUM_SIZE: usize = (std::mem::size_of::<TagIdIntType>() * 8) as usize;
+pub const MAX_ENUM_SIZE: usize = std::mem::size_of::<TagIdIntType>() * 8;
 const GENERATE_NULLABLE: bool = true;
 
 #[derive(Debug, Clone, Copy)]
@@ -898,7 +898,7 @@ impl<'a> UnionLayout<'a> {
             } => {
                 debug_assert_ne!(nullable_id, tag_id != 0);
 
-                other_fields[index as usize]
+                other_fields[index]
             }
         };
 
diff --git a/crates/compiler/mono/src/reset_reuse.rs b/crates/compiler/mono/src/reset_reuse.rs
index ac57ca2fdc..e47cbff03c 100644
--- a/crates/compiler/mono/src/reset_reuse.rs
+++ b/crates/compiler/mono/src/reset_reuse.rs
@@ -1128,8 +1128,8 @@ impl<'a> ReuseEnvironment<'a> {
 /**
 Check if a layout can be reused. by verifying if the layout is a union and if the tag is not nullable.
 */
-fn can_reuse_layout<'a, 'i>(
-    layout_interner: &'i STLayoutInterner<'a>,
+fn can_reuse_layout<'a>(
+    layout_interner: &STLayoutInterner<'a>,
     environment: &ReuseEnvironment<'a>,
     layout: &InLayout<'a>,
 ) -> Reuse {
diff --git a/crates/compiler/region/src/all.rs b/crates/compiler/region/src/all.rs
index f2b188b104..9b556b76b4 100644
--- a/crates/compiler/region/src/all.rs
+++ b/crates/compiler/region/src/all.rs
@@ -105,14 +105,14 @@ impl Position {
     #[must_use]
     pub const fn bump_column(self, count: u32) -> Self {
         Self {
-            offset: self.offset + count as u32,
+            offset: self.offset + count,
         }
     }
 
     #[must_use]
     pub fn bump_invisible(self, count: u32) -> Self {
         Self {
-            offset: self.offset + count as u32,
+            offset: self.offset + count,
         }
     }
 
@@ -126,7 +126,7 @@ impl Position {
     #[must_use]
     pub const fn sub(self, count: u32) -> Self {
         Self {
-            offset: self.offset - count as u32,
+            offset: self.offset - count,
         }
     }
 
@@ -376,7 +376,7 @@ impl LineInfo {
         let column = offset - self.line_offsets[line];
         LineColumn {
             line: line as u32,
-            column: column as u32,
+            column,
         }
     }
 
diff --git a/crates/compiler/solve/src/solve.rs b/crates/compiler/solve/src/solve.rs
index 349e8427dc..00a5b0d9a3 100644
--- a/crates/compiler/solve/src/solve.rs
+++ b/crates/compiler/solve/src/solve.rs
@@ -2537,14 +2537,14 @@ enum TypeToVar {
 }
 
 #[allow(clippy::too_many_arguments)]
-fn type_to_variable<'a>(
+fn type_to_variable(
     subs: &mut Subs,
     rank: Rank,
     pools: &mut Pools,
     problems: &mut Vec<TypeError>,
     abilities_store: &AbilitiesStore,
     obligation_cache: &mut ObligationCache,
-    arena: &'a bumpalo::Bump,
+    arena: &bumpalo::Bump,
     aliases: &mut Aliases,
     types: &mut Types,
     typ: Index<TypeTag>,
diff --git a/crates/compiler/solve/src/specialize.rs b/crates/compiler/solve/src/specialize.rs
index 7ba2fe5799..d6344f70fc 100644
--- a/crates/compiler/solve/src/specialize.rs
+++ b/crates/compiler/solve/src/specialize.rs
@@ -545,7 +545,7 @@ fn compact_lambda_set<P: Phase>(
         Err(()) => {
             // Do nothing other than to remove the concrete lambda to drop from the lambda set,
             // which we already did in 1b above.
-            trace_compact!(3iter_end_skipped. subs, t_f1);
+            trace_compact!(3iter_end_skipped.subs, t_f1);
             return OneCompactionResult::Compacted {
                 new_obligations: Default::default(),
                 new_lambda_sets_to_specialize: Default::default(),
@@ -568,7 +568,7 @@ fn compact_lambda_set<P: Phase>(
         Err(()) => {
             // Do nothing other than to remove the concrete lambda to drop from the lambda set,
             // which we already did in 1b above.
-            trace_compact!(3iter_end_skipped. subs, t_f1);
+            trace_compact!(3iter_end_skipped.subs, t_f1);
             return OneCompactionResult::Compacted {
                 new_obligations: Default::default(),
                 new_lambda_sets_to_specialize: Default::default(),
@@ -581,7 +581,7 @@ fn compact_lambda_set<P: Phase>(
     let t_f2 = deep_copy_var_in(subs, target_rank, pools, t_f2, arena);
 
     // 3. Unify `t_f1 ~ t_f2`.
-    trace_compact!(3iter_start. subs, this_lambda_set, t_f1, t_f2);
+    trace_compact!(3iter_start.subs, this_lambda_set, t_f1, t_f2);
     let (vars, new_obligations, new_lambda_sets_to_specialize, _meta) = unify(
         &mut UEnv::new(subs),
         t_f1,
@@ -590,7 +590,7 @@ fn compact_lambda_set<P: Phase>(
         Polarity::Pos,
     )
     .expect_success("ambient functions don't unify");
-    trace_compact!(3iter_end. subs, t_f1);
+    trace_compact!(3iter_end.subs, t_f1);
 
     introduce(subs, target_rank, pools, &vars);
 
diff --git a/crates/compiler/types/src/pretty_print.rs b/crates/compiler/types/src/pretty_print.rs
index 25527f0f72..590d410f02 100644
--- a/crates/compiler/types/src/pretty_print.rs
+++ b/crates/compiler/types/src/pretty_print.rs
@@ -1285,8 +1285,8 @@ fn write_flat_type<'a>(
     }
 }
 
-pub fn push_union<'a, L: Label>(
-    subs: &'a Subs,
+pub fn push_union<L: Label>(
+    subs: &Subs,
     tags: &UnionLabels<L>,
     fields: &mut Vec<(L, Vec<Variable>)>,
 ) {
diff --git a/crates/compiler/unify/src/unify.rs b/crates/compiler/unify/src/unify.rs
index 4b6d737dfb..95bf05d78e 100644
--- a/crates/compiler/unify/src/unify.rs
+++ b/crates/compiler/unify/src/unify.rs
@@ -1360,8 +1360,8 @@ fn separate_union_lambdas<M: MetaCollector>(
     let mut buckets: VecMap<Symbol, Sides> = VecMap::with_capacity(fields1.len() + fields2.len());
 
     let (mut fields_left, mut fields_right) = (
-        fields1.iter_all().into_iter().peekable(),
-        fields2.iter_all().into_iter().peekable(),
+        fields1.iter_all().peekable(),
+        fields2.iter_all().peekable(),
     );
 
     loop {
diff --git a/crates/repl_wasm/build.rs b/crates/repl_wasm/build.rs
index 0ed3b1b4dd..7cb3d02149 100644
--- a/crates/repl_wasm/build.rs
+++ b/crates/repl_wasm/build.rs
@@ -31,7 +31,7 @@ fn main() {
     let builtins_host_tempfile = roc_bitcode::host_wasm_tempfile()
         .expect("failed to write host builtins object to tempfile");
 
-    let output = Command::new(&zig_executable())
+    let output = Command::new(zig_executable())
         .args([
             "wasm-ld",
             builtins_host_tempfile.path().to_str().unwrap(),
@@ -67,7 +67,7 @@ fn build_wasm_platform(out_dir: &str, source_path: &str) -> PathBuf {
     let mut platform_obj = PathBuf::from(out_dir).join(PLATFORM_FILENAME);
     platform_obj.set_extension(OBJECT_EXTENSION);
 
-    Command::new(&zig_executable())
+    Command::new(zig_executable())
         .args([
             "build-lib",
             "-target",
diff --git a/crates/vendor/pathfinding/src/lib.rs b/crates/vendor/pathfinding/src/lib.rs
index 8044a7fed9..6846cc276c 100644
--- a/crates/vendor/pathfinding/src/lib.rs
+++ b/crates/vendor/pathfinding/src/lib.rs
@@ -219,7 +219,7 @@ where
         })
         .collect();
     if prev_group.is_empty() {
-        let remaining: Vec<N> = preds_map.into_iter().map(|(node, _)| node).collect();
+        let remaining: Vec<N> = preds_map.into_keys().collect();
         return Err((Vec::new(), remaining));
     }
     for node in &prev_group {
@@ -241,7 +241,7 @@ where
         }
         groups.push(mem::replace(&mut prev_group, next_group));
         if prev_group.is_empty() {
-            let remaining: Vec<N> = preds_map.into_iter().map(|(node, _)| node).collect();
+            let remaining: Vec<N> = preds_map.into_keys().collect();
             return Err((groups, remaining));
         }
     }
diff --git a/crates/wasi-libc-sys/build.rs b/crates/wasi-libc-sys/build.rs
index 1ef3bda1ea..74a2cd6a37 100644
--- a/crates/wasi-libc-sys/build.rs
+++ b/crates/wasi-libc-sys/build.rs
@@ -38,7 +38,7 @@ fn main() {
         .unwrap();
 
     // Copy libc to where Cargo expects the output of this crate
-    fs::copy(&libc_path, &out_file).unwrap();
+    fs::copy(libc_path, &out_file).unwrap();
 
     println!(
         "cargo:rustc-env=WASI_LIBC_PATH={}",
diff --git a/crates/wasm_interp/src/instance.rs b/crates/wasm_interp/src/instance.rs
index 036d092597..8454a384d1 100644
--- a/crates/wasm_interp/src/instance.rs
+++ b/crates/wasm_interp/src/instance.rs
@@ -948,7 +948,7 @@ impl<'a, I: ImportDispatcher> Instance<'a, I> {
                 let memory_index = self.fetch_immediate_u32(module);
                 assert_eq!(memory_index, 0);
                 let old_bytes = self.memory.len() as u32;
-                let old_pages = old_bytes / MemorySection::PAGE_SIZE as u32;
+                let old_pages = old_bytes / MemorySection::PAGE_SIZE;
                 let grow_pages = self.value_store.pop_u32()?;
                 let grow_bytes = grow_pages * MemorySection::PAGE_SIZE;
                 let new_bytes = old_bytes + grow_bytes;
@@ -1700,7 +1700,7 @@ impl<'a, I: ImportDispatcher> Instance<'a, I> {
             } else {
                 // For calls, we print special debug stuff in do_call
                 let base = self.current_frame.locals_start + self.current_frame.locals_count;
-                let slice = self.value_store.get_slice(base as usize);
+                let slice = self.value_store.get_slice(base);
                 eprintln!("{:06x} {:17} {:x?}", file_offset, debug_string, slice);
             }
             let is_return = op_code == RETURN || (op_code == END && implicit_return);
diff --git a/crates/wasm_interp/src/tests/test_basics.rs b/crates/wasm_interp/src/tests/test_basics.rs
index 94791ee696..c0b56cec85 100644
--- a/crates/wasm_interp/src/tests/test_basics.rs
+++ b/crates/wasm_interp/src/tests/test_basics.rs
@@ -37,7 +37,7 @@ fn test_loop_help(end: i32, expected: i32) {
 
         // loop <void>
         buf.push(OpCode::LOOP as u8);
-        buf.push(ValueType::VOID as u8);
+        buf.push(ValueType::VOID);
 
         //   local.get $i
         buf.push(OpCode::GETLOCAL as u8);
@@ -135,7 +135,7 @@ fn test_if_else_help(condition: i32, expected: i32) {
 
         // if <blocktype>
         buf.push(OpCode::IF as u8);
-        buf.push(ValueType::VOID as u8);
+        buf.push(ValueType::VOID);
 
         // i32.const 111
         buf.push(OpCode::I32CONST as u8);
@@ -599,7 +599,7 @@ fn test_call_return_no_args() {
         ValueType::I32 as u8,
         OpCode::BLOCK as u8, /*  */
         // call from inside a block. callee's implicit return should still work correctly.
-        ValueType::VOID as u8,
+        ValueType::VOID,
         OpCode::CALL as u8,
         1, // function 1
         OpCode::SETLOCAL as u8,
diff --git a/devtools/flake.lock b/devtools/flake.lock
index 188156be58..133ab3f20c 100644
--- a/devtools/flake.lock
+++ b/devtools/flake.lock
@@ -1,12 +1,15 @@
 {
   "nodes": {
     "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
       "locked": {
-        "lastModified": 1667395993,
-        "narHash": "sha256-nuEHfE/LcWyuSWnS8t12N1wc105Qtau+/OdUAjtQ0rA=",
+        "lastModified": 1681202837,
+        "narHash": "sha256-H+Rh19JDwRtpVPAWp64F+rlEtxUWBAQW28eAi3SRSzg=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "5aed5285a952e0b949eb3ba02c12fa4fcfef535f",
+        "rev": "cfacdce06f30d2b68473a46042957675eebb3401",
         "type": "github"
       },
       "original": {
@@ -84,11 +87,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1673134516,
-        "narHash": "sha256-mAZQKqkNQbBmJnmUU0blOfkKlgMSSVyPHdeWeuKad8U=",
+        "lastModified": 1673796341,
+        "narHash": "sha256-1kZi9OkukpNmOaPY7S5/+SlCDOuYnP3HkXHvNDyLQcc=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "f6f44561884c3470e2b783683d5dbac42dfc833b",
+        "rev": "6dccdc458512abce8d19f74195bb20fdb067df50",
         "type": "github"
       },
       "original": {
@@ -106,8 +109,8 @@
         "rust-overlay": "rust-overlay"
       },
       "locked": {
-        "lastModified": 1673266343,
-        "narHash": "sha256-HQGjNhCte1wgvo5/SUL1OjIpfoUCQ8vC/2k0gi7UtmQ=",
+        "lastModified": 1681824025,
+        "narHash": "sha256-ZMFUKoJ03ZY2qmulhpL4i6J0q0fm2Rc/yjo9f7geCZ4=",
         "path": "/home/username/gitrepos/roc1/roc",
         "type": "path"
       },
@@ -131,11 +134,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1673231106,
-        "narHash": "sha256-Tbw4N/TL+nHmxF8RBoOJbl/6DRRzado/9/ttPEzkGr8=",
+        "lastModified": 1673922364,
+        "narHash": "sha256-U0XIY/Y/x4fFtlCZKMtWlqOYUnLiXj4F42GQHxWuPow=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "3488cec01351c2f1086b02a3a61808be7a25103e",
+        "rev": "4e0f9b8a5102387f8d19901bced16a256a6ccdc7",
         "type": "github"
       },
       "original": {
@@ -143,6 +146,21 @@
         "repo": "rust-overlay",
         "type": "github"
       }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
     }
   },
   "root": "root",
diff --git a/devtools/flake.nix b/devtools/flake.nix
index f63f90d792..a57c192eaf 100644
--- a/devtools/flake.nix
+++ b/devtools/flake.nix
@@ -1,5 +1,5 @@
 {
-  description = "Allows sharing dependencies between dev tools and roc";
+  description = "Allows sharing dependencies between dev tools and roc. Prevents version GLIBC_2.36 not found.";
 
   inputs = {
     # change this path to the path of your roc folder
@@ -24,7 +24,7 @@
             vscodeWithExtensions = pkgs.vscode-with-extensions.override {
               vscodeExtensions = with pkgs.vscode-extensions; [
                 matklad.rust-analyzer
-                eamodio.gitlens
+                # eamodio.gitlens
                 bbenoist.nix
                 vadimcn.vscode-lldb
                 tamasfe.even-better-toml
@@ -33,13 +33,12 @@
                      {
                         name = "roc-lang-support";
                         publisher = "benjamin-thomas";
-                        version = "0.0.3";
+                        version = "0.0.4";
                         # keep this sha for the first run, nix will tell you the correct one to change it to
                         sha256 = "sha256-mabNegZ+XPQ6EIHFk6jz2mAPLHAU6Pm3w0SiFB7IE+s=";
                       }
                     ]
                   ;
-
             };
           in [ vscodeWithExtensions devInputs ];
 
diff --git a/examples/platform-switching/rust-platform/rust-toolchain.toml b/examples/platform-switching/rust-platform/rust-toolchain.toml
index 1932d9560f..2cb7a980c5 100644
--- a/examples/platform-switching/rust-platform/rust-toolchain.toml
+++ b/examples/platform-switching/rust-platform/rust-toolchain.toml
@@ -1,5 +1,5 @@
 [toolchain]
-channel = "1.65.0"
+channel = "1.68.2"
 
 profile = "default"
 
diff --git a/flake.lock b/flake.lock
index 1715e271fa..22e5d0f256 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,12 +1,15 @@
 {
   "nodes": {
     "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
       "locked": {
-        "lastModified": 1667395993,
-        "narHash": "sha256-nuEHfE/LcWyuSWnS8t12N1wc105Qtau+/OdUAjtQ0rA=",
+        "lastModified": 1681202837,
+        "narHash": "sha256-H+Rh19JDwRtpVPAWp64F+rlEtxUWBAQW28eAi3SRSzg=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "5aed5285a952e0b949eb3ba02c12fa4fcfef535f",
+        "rev": "cfacdce06f30d2b68473a46042957675eebb3401",
         "type": "github"
       },
       "original": {
@@ -31,12 +34,15 @@
       }
     },
     "flake-utils_3": {
+      "inputs": {
+        "systems": "systems_2"
+      },
       "locked": {
-        "lastModified": 1659877975,
-        "narHash": "sha256-zllb8aq3YO3h8B/U0/J1WBgAL8EX5yWf5pMj3G0NAmc=",
+        "lastModified": 1681202837,
+        "narHash": "sha256-H+Rh19JDwRtpVPAWp64F+rlEtxUWBAQW28eAi3SRSzg=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "c0e246b9b83f637f4681389ecabcb2681b4f3af0",
+        "rev": "cfacdce06f30d2b68473a46042957675eebb3401",
         "type": "github"
       },
       "original": {
@@ -53,11 +59,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1672992692,
-        "narHash": "sha256-/eLQLSNIa22ARTZbk+x8i0iE8khe1eiHWkuxgTVXZ7g=",
+        "lastModified": 1676383589,
+        "narHash": "sha256-KCkWZXCjH+C4Kn7fUGSrEl5btk+sERHhZueSsvVbPWc=",
         "owner": "guibou",
         "repo": "nixGL",
-        "rev": "643e730efb981ffaf8478f441ec9b9aeea1c89f5",
+        "rev": "c917918ab9ebeee27b0dd657263d3f57ba6bb8ad",
         "type": "github"
       },
       "original": {
@@ -98,11 +104,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1673922364,
-        "narHash": "sha256-U0XIY/Y/x4fFtlCZKMtWlqOYUnLiXj4F42GQHxWuPow=",
+        "lastModified": 1682043560,
+        "narHash": "sha256-ZsF4Yee9pQbvLtwSVGgYux+az4yFSLXrxPyGHm3ptJM=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "4e0f9b8a5102387f8d19901bced16a256a6ccdc7",
+        "rev": "48037a6f8faeee138ede96bf607bc95c9dab9aec",
         "type": "github"
       },
       "original": {
@@ -110,6 +116,36 @@
         "repo": "rust-overlay",
         "type": "github"
       }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "systems_2": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
     }
   },
   "root": "root",
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index 8751835c29..96742690cc 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -3,14 +3,14 @@
 #  - update `channel = "RUST_VERSION"`
 #  - update `channel = "RUST_VERSION"` in examples/platform-switching/rust-platform/rust-toolchain.toml
 #  - to update the nightly version:
-#     - Find the latest nightly release that matches RUST_VERSION here: https://github.com/oxalica/rust-overlay/tree/master/manifests/nightly/2022
+#     - Find the latest nightly release that matches RUST_VERSION here: https://github.com/oxalica/rust-overlay/tree/master/manifests/nightly/2023
 #     - update `channel = "nightly-OLD_DATE"` below
 #     - update nightly-OLD_DATE in .github/workflows/windows.yml
 #     - update nightly-OLD_DATE in crates/compiler/build/src/link.rs
 
-channel = "1.65.0" # check ^^^ when changing this
-# 
-# channel = "nightly-2022-09-17" # 1.65 nightly to be able to use unstable features
+channel = "1.68.2" # check ^^^ when changing this
+#
+# channel = "nightly-2023-01-22" # 1.68.0 nightly to be able to use unstable features
 profile = "default"
 components = [
     # for usages of rust-analyzer or similar tools inside `nix develop`