diff --git a/ast/src/canonicalization/module.rs b/ast/src/canonicalization/module.rs
index 64c568af5f..634e7e881c 100644
--- a/ast/src/canonicalization/module.rs
+++ b/ast/src/canonicalization/module.rs
@@ -7,6 +7,7 @@ use roc_can::operator::desugar_def;
 use roc_collections::all::{default_hasher, ImMap, ImSet, MutMap, MutSet, SendMap};
 use roc_module::ident::Ident;
 use roc_module::ident::Lowercase;
+use roc_module::symbol::IdentIdsByModule;
 use roc_module::symbol::{IdentIds, ModuleId, ModuleIds, Symbol};
 use roc_parse::ast;
 use roc_parse::pattern::PatternType;
@@ -48,7 +49,7 @@ pub fn canonicalize_module_defs<'a>(
     home: ModuleId,
     module_ids: &ModuleIds,
     exposed_ident_ids: IdentIds,
-    dep_idents: MutMap<ModuleId, IdentIds>,
+    dep_idents: IdentIdsByModule,
     aliases: MutMap<Symbol, Alias>,
     exposed_imports: MutMap<Ident, (Symbol, Region)>,
     mut exposed_symbols: MutSet<Symbol>,
diff --git a/ast/src/lang/env.rs b/ast/src/lang/env.rs
index 0af9303543..d2ea5448bd 100644
--- a/ast/src/lang/env.rs
+++ b/ast/src/lang/env.rs
@@ -2,7 +2,7 @@ use crate::mem_pool::pool::{NodeId, Pool};
 use bumpalo::{collections::Vec as BumpVec, Bump};
 use roc_collections::all::{MutMap, MutSet};
 use roc_module::ident::{Ident, Lowercase, ModuleName};
-use roc_module::symbol::{IdentIds, ModuleId, ModuleIds, Symbol};
+use roc_module::symbol::{IdentIds, IdentIdsByModule, ModuleId, ModuleIds, Symbol};
 use roc_problem::can::{Problem, RuntimeError};
 use roc_region::all::{Loc, Region};
 use roc_types::subs::VarStore;
@@ -19,7 +19,7 @@ pub struct Env<'a> {
 
     pub problems: BumpVec<'a, Problem>,
 
-    pub dep_idents: MutMap<ModuleId, IdentIds>,
+    pub dep_idents: IdentIdsByModule,
     pub module_ids: &'a ModuleIds,
     pub ident_ids: IdentIds,
     pub exposed_ident_ids: IdentIds,
@@ -41,7 +41,7 @@ impl<'a> Env<'a> {
         arena: &'a Bump,
         pool: &'a mut Pool,
         var_store: &'a mut VarStore,
-        dep_idents: MutMap<ModuleId, IdentIds>,
+        dep_idents: IdentIdsByModule,
         module_ids: &'a ModuleIds,
         exposed_ident_ids: IdentIds,
     ) -> Env<'a> {
diff --git a/ast/src/lang/scope.rs b/ast/src/lang/scope.rs
index 1f57b4360b..ced87957e4 100644
--- a/ast/src/lang/scope.rs
+++ b/ast/src/lang/scope.rs
@@ -12,7 +12,8 @@ use crate::mem_pool::shallow_clone::ShallowClone;
 use roc_collections::all::{MutMap, MutSet};
 use roc_module::ident::{Ident, Lowercase};
 use roc_module::symbol::{
-    get_module_ident_ids, get_module_ident_ids_mut, IdentIds, Interns, ModuleId, Symbol,
+    get_module_ident_ids, get_module_ident_ids_mut, IdentIds, IdentIdsByModule, Interns, ModuleId,
+    Symbol,
 };
 use roc_problem::can::RuntimeError;
 use roc_region::all::{Loc, Region};
@@ -320,11 +321,7 @@ impl Scope {
         self.aliases.contains_key(&name)
     }
 
-    pub fn fill_scope(
-        &mut self,
-        env: &Env,
-        all_ident_ids: &mut MutMap<ModuleId, IdentIds>,
-    ) -> ASTResult<()> {
+    pub fn fill_scope(&mut self, env: &Env, all_ident_ids: &mut IdentIdsByModule) -> ASTResult<()> {
         let ident_ids = get_module_ident_ids(all_ident_ids, &env.home)?.clone();
 
         for (_, ident_ref) in ident_ids.ident_strs() {
diff --git a/compiler/can/src/def.rs b/compiler/can/src/def.rs
index a5413def46..bf7520dbcd 100644
--- a/compiler/can/src/def.rs
+++ b/compiler/can/src/def.rs
@@ -984,7 +984,7 @@ fn add_annotation_aliases(
     aliases: &mut VecMap<Symbol, Alias>,
 ) {
     for (name, alias) in type_annotation.aliases.iter() {
-        if !aliases.contains(name) {
+        if !aliases.contains_key(name) {
             aliases.insert(*name, alias.clone());
         }
     }
diff --git a/compiler/can/src/env.rs b/compiler/can/src/env.rs
index 2c7a28ad69..e127c32bea 100644
--- a/compiler/can/src/env.rs
+++ b/compiler/can/src/env.rs
@@ -1,7 +1,7 @@
 use crate::procedure::References;
 use roc_collections::{MutMap, VecSet};
 use roc_module::ident::{Ident, Lowercase, ModuleName};
-use roc_module::symbol::{IdentIds, ModuleId, ModuleIds, Symbol};
+use roc_module::symbol::{IdentIds, IdentIdsByModule, ModuleId, ModuleIds, Symbol};
 use roc_problem::can::{Problem, RuntimeError};
 use roc_region::all::{Loc, Region};
 
@@ -11,7 +11,7 @@ pub struct Env<'a> {
     /// are assumed to be relative to this path.
     pub home: ModuleId,
 
-    pub dep_idents: &'a MutMap<ModuleId, IdentIds>,
+    pub dep_idents: &'a IdentIdsByModule,
 
     pub module_ids: &'a ModuleIds,
 
@@ -42,7 +42,7 @@ pub struct Env<'a> {
 impl<'a> Env<'a> {
     pub fn new(
         home: ModuleId,
-        dep_idents: &'a MutMap<ModuleId, IdentIds>,
+        dep_idents: &'a IdentIdsByModule,
         module_ids: &'a ModuleIds,
         exposed_ident_ids: IdentIds,
     ) -> Env<'a> {
diff --git a/compiler/can/src/module.rs b/compiler/can/src/module.rs
index db8cd17b1c..0db77094cc 100644
--- a/compiler/can/src/module.rs
+++ b/compiler/can/src/module.rs
@@ -10,7 +10,7 @@ use bumpalo::Bump;
 use roc_collections::{MutMap, SendMap, VecSet};
 use roc_module::ident::Ident;
 use roc_module::ident::Lowercase;
-use roc_module::symbol::{IdentIds, ModuleId, ModuleIds, Symbol};
+use roc_module::symbol::{IdentIds, IdentIdsByModule, ModuleId, ModuleIds, Symbol};
 use roc_parse::ast;
 use roc_parse::header::HeaderFor;
 use roc_parse::pattern::PatternType;
@@ -170,7 +170,7 @@ pub fn canonicalize_module_defs<'a>(
     home: ModuleId,
     module_ids: &ModuleIds,
     exposed_ident_ids: IdentIds,
-    dep_idents: &'a MutMap<ModuleId, IdentIds>,
+    dep_idents: &'a IdentIdsByModule,
     aliases: MutMap<Symbol, Alias>,
     exposed_imports: MutMap<Ident, (Symbol, Region)>,
     exposed_symbols: &VecSet<Symbol>,
diff --git a/compiler/collections/src/vec_map.rs b/compiler/collections/src/vec_map.rs
index 60b1608737..68de20f849 100644
--- a/compiler/collections/src/vec_map.rs
+++ b/compiler/collections/src/vec_map.rs
@@ -54,7 +54,7 @@ impl<K: PartialEq, V> VecMap<K, V> {
         }
     }
 
-    pub fn contains(&self, key: &K) -> bool {
+    pub fn contains_key(&self, key: &K) -> bool {
         self.keys.contains(key)
     }
 
@@ -69,6 +69,34 @@ impl<K: PartialEq, V> VecMap<K, V> {
         }
     }
 
+    pub fn get(&self, key: &K) -> Option<&V> {
+        match self.keys.iter().position(|x| x == key) {
+            None => None,
+            Some(index) => Some(&self.values[index]),
+        }
+    }
+
+    pub fn get_mut(&mut self, key: &K) -> Option<&mut V> {
+        match self.keys.iter().position(|x| x == key) {
+            None => None,
+            Some(index) => Some(&mut self.values[index]),
+        }
+    }
+
+    pub fn get_or_insert(&mut self, key: K, default_value: impl Fn() -> V) -> &mut V {
+        match self.keys.iter().position(|x| x == &key) {
+            Some(index) => &mut self.values[index],
+            None => {
+                let value = default_value();
+
+                self.keys.push(key);
+                self.values.push(value);
+
+                self.values.last_mut().unwrap()
+            }
+        }
+    }
+
     pub fn iter(&self) -> impl Iterator<Item = (&K, &V)> {
         self.keys.iter().zip(self.values.iter())
     }
diff --git a/compiler/load_internal/src/file.rs b/compiler/load_internal/src/file.rs
index 20584442b3..3b5acebcc6 100644
--- a/compiler/load_internal/src/file.rs
+++ b/compiler/load_internal/src/file.rs
@@ -18,8 +18,8 @@ use roc_constrain::module::{
 use roc_error_macros::internal_error;
 use roc_module::ident::{Ident, ModuleName, QualifiedModuleName, TagName};
 use roc_module::symbol::{
-    IdentIds, Interns, ModuleId, ModuleIds, PQModuleName, PackageModuleIds, PackageQualified,
-    Symbol,
+    IdentIds, IdentIdsByModule, Interns, ModuleId, ModuleIds, PQModuleName, PackageModuleIds,
+    PackageQualified, Symbol,
 };
 use roc_mono::ir::{
     CapturedSymbols, EntryPoint, ExternalSpecializations, PartialProc, Proc, ProcLayout, Procs,
@@ -168,6 +168,8 @@ impl Default for ModuleCache<'_> {
     }
 }
 
+type SharedIdentIdsByModule = Arc<Mutex<roc_module::symbol::IdentIdsByModule>>;
+
 fn start_phase<'a>(
     module_id: ModuleId,
     phase: Phase,
@@ -228,8 +230,7 @@ fn start_phase<'a>(
 
                 let deps_by_name = &parsed.deps_by_name;
                 let num_deps = deps_by_name.len();
-                let mut dep_idents: MutMap<ModuleId, IdentIds> =
-                    IdentIds::exposed_builtins(num_deps);
+                let mut dep_idents: IdentIdsByModule = IdentIds::exposed_builtins(num_deps);
 
                 let State {
                     ident_ids_by_module,
@@ -419,7 +420,7 @@ pub struct LoadedModule {
     pub type_problems: MutMap<ModuleId, Vec<solve::TypeError>>,
     pub declarations_by_id: MutMap<ModuleId, Vec<Declaration>>,
     pub exposed_to_host: MutMap<Symbol, Variable>,
-    pub dep_idents: MutMap<ModuleId, IdentIds>,
+    pub dep_idents: IdentIdsByModule,
     pub exposed_aliases: MutMap<Symbol, Alias>,
     pub exposed_values: Vec<Symbol>,
     pub sources: MutMap<ModuleId, (PathBuf, Box<str>)>,
@@ -483,7 +484,7 @@ struct ConstrainedModule {
     constraint: ConstraintSoa,
     ident_ids: IdentIds,
     var_store: VarStore,
-    dep_idents: MutMap<ModuleId, IdentIds>,
+    dep_idents: IdentIdsByModule,
     module_timing: ModuleTiming,
 }
 
@@ -587,7 +588,7 @@ enum Msg<'a> {
         solved_module: SolvedModule,
         solved_subs: Solved<Subs>,
         decls: Vec<Declaration>,
-        dep_idents: MutMap<ModuleId, IdentIds>,
+        dep_idents: IdentIdsByModule,
         module_timing: ModuleTiming,
         abilities_store: AbilitiesStore,
     },
@@ -595,7 +596,7 @@ enum Msg<'a> {
         solved_subs: Solved<Subs>,
         exposed_vars_by_symbol: Vec<(Symbol, Variable)>,
         exposed_aliases_by_symbol: MutMap<Symbol, (bool, Alias)>,
-        dep_idents: MutMap<ModuleId, IdentIds>,
+        dep_idents: IdentIdsByModule,
         documentation: MutMap<ModuleId, ModuleDocumentation>,
         abilities_store: AbilitiesStore,
     },
@@ -668,13 +669,13 @@ struct State<'a> {
 
     /// This is the "final" list of IdentIds, after canonicalization and constraint gen
     /// have completed for a given module.
-    pub constrained_ident_ids: MutMap<ModuleId, IdentIds>,
+    pub constrained_ident_ids: IdentIdsByModule,
 
     /// From now on, these will be used by multiple threads; time to make an Arc<Mutex<_>>!
     pub arc_modules: Arc<Mutex<PackageModuleIds<'a>>>,
     pub arc_shorthands: Arc<Mutex<MutMap<&'a str, PackageName<'a>>>>,
 
-    pub ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    pub ident_ids_by_module: SharedIdentIdsByModule,
 
     pub declarations_by_id: MutMap<ModuleId, Vec<Declaration>>,
 
@@ -705,7 +706,7 @@ impl<'a> State<'a> {
         goal_phase: Phase,
         exposed_types: ExposedByModule,
         arc_modules: Arc<Mutex<PackageModuleIds<'a>>>,
-        ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+        ident_ids_by_module: SharedIdentIdsByModule,
         cached_subs: MutMap<ModuleId, (Subs, Vec<(Symbol, Variable)>)>,
         render: RenderTarget,
     ) -> Self {
@@ -814,7 +815,7 @@ enum BuildTask<'a> {
         module_name: PQModuleName<'a>,
         module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
         shorthands: Arc<Mutex<MutMap<&'a str, PackageName<'a>>>>,
-        ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+        ident_ids_by_module: SharedIdentIdsByModule,
     },
     Parse {
         header: ModuleHeader<'a>,
@@ -822,7 +823,7 @@ enum BuildTask<'a> {
     CanonicalizeAndConstrain {
         parsed: ParsedModule<'a>,
         module_ids: ModuleIds,
-        dep_idents: MutMap<ModuleId, IdentIds>,
+        dep_idents: IdentIdsByModule,
         exposed_symbols: VecSet<Symbol>,
         aliases: MutMap<Symbol, Alias>,
         skip_constraint_gen: bool,
@@ -837,7 +838,7 @@ enum BuildTask<'a> {
         constraint: ConstraintSoa,
         var_store: VarStore,
         declarations: Vec<Declaration>,
-        dep_idents: MutMap<ModuleId, IdentIds>,
+        dep_idents: IdentIdsByModule,
         cached_subs: CachedSubs,
     },
     BuildPendingSpecializations {
@@ -951,7 +952,7 @@ pub enum PrintTarget {
 
 pub struct LoadStart<'a> {
     arc_modules: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
     root_id: ModuleId,
     root_msg: Msg<'a>,
 }
@@ -2403,7 +2404,7 @@ fn finish(
     solved: Solved<Subs>,
     exposed_aliases_by_symbol: MutMap<Symbol, Alias>,
     exposed_vars_by_symbol: Vec<(Symbol, Variable)>,
-    dep_idents: MutMap<ModuleId, IdentIds>,
+    dep_idents: IdentIdsByModule,
     documentation: MutMap<ModuleId, ModuleDocumentation>,
     abilities_store: AbilitiesStore,
 ) -> LoadedModule {
@@ -2451,7 +2452,7 @@ fn load_pkg_config<'a>(
     shorthand: &'a str,
     app_module_id: ModuleId,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
 ) -> Result<Msg<'a>, LoadingProblem<'a>> {
     let module_start_time = SystemTime::now();
 
@@ -2569,7 +2570,7 @@ fn load_builtin_module_help<'a>(
 fn load_builtin_module<'a>(
     arena: &'a Bump,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
     module_timing: ModuleTiming,
     module_id: ModuleId,
     module_name: &str,
@@ -2594,7 +2595,7 @@ fn load_module<'a>(
     module_name: PQModuleName<'a>,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
     arc_shorthands: Arc<Mutex<MutMap<&'a str, PackageName<'a>>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
 ) -> Result<(ModuleId, Msg<'a>), LoadingProblem<'a>> {
     let module_start_time = SystemTime::now();
 
@@ -2781,7 +2782,7 @@ fn parse_header<'a>(
     is_root_module: bool,
     opt_shorthand: Option<&'a str>,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
     src_bytes: &'a [u8],
     start_time: SystemTime,
 ) -> Result<(ModuleId, Msg<'a>), LoadingProblem<'a>> {
@@ -2969,7 +2970,7 @@ fn load_filename<'a>(
     is_root_module: bool,
     opt_shorthand: Option<&'a str>,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
     module_start_time: SystemTime,
 ) -> Result<(ModuleId, Msg<'a>), LoadingProblem<'a>> {
     let file_io_start = SystemTime::now();
@@ -3003,7 +3004,7 @@ fn load_from_str<'a>(
     filename: PathBuf,
     src: &'a str,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
     module_start_time: SystemTime,
 ) -> Result<(ModuleId, Msg<'a>), LoadingProblem<'a>> {
     let file_io_start = SystemTime::now();
@@ -3039,7 +3040,7 @@ fn send_header<'a>(
     info: HeaderInfo<'a>,
     parse_state: roc_parse::state::State<'a>,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
     module_timing: ModuleTiming,
 ) -> (ModuleId, Msg<'a>) {
     use ModuleNameEnum::*;
@@ -3102,9 +3103,7 @@ fn send_header<'a>(
         home = module_ids.get_or_insert(&name);
 
         // Ensure this module has an entry in the exposed_ident_ids map.
-        ident_ids_by_module
-            .entry(home)
-            .or_insert_with(IdentIds::default);
+        ident_ids_by_module.get_or_insert(home);
 
         // For each of our imports, add an entry to deps_by_name
         //
@@ -3131,9 +3130,7 @@ fn send_header<'a>(
             // Add the new exposed idents to the dep module's IdentIds, so
             // once that module later gets loaded, its lookups will resolve
             // to the same symbols as the ones we're using here.
-            let ident_ids = ident_ids_by_module
-                .entry(module_id)
-                .or_insert_with(IdentIds::default);
+            let ident_ids = ident_ids_by_module.get_or_insert(module_id);
 
             for ident in exposed_idents {
                 let ident_id = ident_ids.get_or_insert(&ident);
@@ -3255,7 +3252,7 @@ fn send_header_two<'a>(
     info: PlatformHeaderInfo<'a>,
     parse_state: roc_parse::state::State<'a>,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
     module_timing: ModuleTiming,
 ) -> (ModuleId, Msg<'a>) {
     let PlatformHeaderInfo {
@@ -3314,9 +3311,7 @@ fn send_header_two<'a>(
         home = module_ids.get_or_insert(&name);
 
         // Ensure this module has an entry in the exposed_ident_ids map.
-        ident_ids_by_module
-            .entry(home)
-            .or_insert_with(IdentIds::default);
+        ident_ids_by_module.get_or_insert(home);
 
         // For each of our imports, add an entry to deps_by_name
         //
@@ -3338,9 +3333,7 @@ fn send_header_two<'a>(
             // Add the new exposed idents to the dep module's IdentIds, so
             // once that module later gets loaded, its lookups will resolve
             // to the same symbols as the ones we're using here.
-            let ident_ids = ident_ids_by_module
-                .entry(module_id)
-                .or_insert_with(IdentIds::default);
+            let ident_ids = ident_ids_by_module.get_or_insert(module_id);
 
             for ident in exposed_idents {
                 let ident_id = ident_ids.get_or_insert(&ident);
@@ -3354,9 +3347,7 @@ fn send_header_two<'a>(
         }
 
         {
-            let ident_ids = ident_ids_by_module
-                .entry(app_module_id)
-                .or_insert_with(IdentIds::default);
+            let ident_ids = ident_ids_by_module.get_or_insert(app_module_id);
 
             for entry in requires {
                 let entry = entry.value;
@@ -3486,7 +3477,7 @@ impl<'a> BuildTask<'a> {
         var_store: VarStore,
         imported_modules: MutMap<ModuleId, Region>,
         exposed_types: &mut ExposedByModule,
-        dep_idents: MutMap<ModuleId, IdentIds>,
+        dep_idents: IdentIdsByModule,
         declarations: Vec<Declaration>,
         cached_subs: CachedSubs,
     ) -> Self {
@@ -3668,7 +3659,7 @@ fn run_solve<'a>(
     constraint: ConstraintSoa,
     var_store: VarStore,
     decls: Vec<Declaration>,
-    dep_idents: MutMap<ModuleId, IdentIds>,
+    dep_idents: IdentIdsByModule,
     cached_subs: CachedSubs,
 ) -> Msg<'a> {
     let solve_start = SystemTime::now();
@@ -3758,7 +3749,7 @@ fn fabricate_pkg_config_module<'a>(
     filename: PathBuf,
     parse_state: roc_parse::state::State<'a>,
     module_ids: Arc<Mutex<PackageModuleIds<'a>>>,
-    ident_ids_by_module: Arc<Mutex<MutMap<ModuleId, IdentIds>>>,
+    ident_ids_by_module: SharedIdentIdsByModule,
     header: &PlatformHeader<'a>,
     module_timing: ModuleTiming,
 ) -> (ModuleId, Msg<'a>) {
@@ -3791,7 +3782,7 @@ fn fabricate_pkg_config_module<'a>(
 fn canonicalize_and_constrain<'a>(
     arena: &'a Bump,
     module_ids: &ModuleIds,
-    dep_idents: MutMap<ModuleId, IdentIds>,
+    dep_idents: IdentIdsByModule,
     exposed_symbols: VecSet<Symbol>,
     aliases: MutMap<Symbol, Alias>,
     parsed: ParsedModule<'a>,
@@ -4576,7 +4567,7 @@ fn to_file_problem_report(filename: &Path, error: io::ErrorKind) -> String {
 fn to_parse_problem_report<'a>(
     problem: FileError<'a, SyntaxError<'a>>,
     mut module_ids: ModuleIds,
-    all_ident_ids: MutMap<ModuleId, IdentIds>,
+    all_ident_ids: IdentIdsByModule,
     render: RenderTarget,
 ) -> String {
     use roc_reporting::report::{parse_problem, RocDocAllocator, DEFAULT_PALETTE};
diff --git a/compiler/module/src/symbol.rs b/compiler/module/src/symbol.rs
index 6f30cd0f6f..7043223a93 100644
--- a/compiler/module/src/symbol.rs
+++ b/compiler/module/src/symbol.rs
@@ -1,6 +1,6 @@
 use crate::ident::{Ident, ModuleName};
 use crate::module_err::{IdentIdNotFound, ModuleIdNotFound, ModuleResult};
-use roc_collections::all::{default_hasher, MutMap, SendMap};
+use roc_collections::{default_hasher, MutMap, SendMap, VecMap};
 use roc_ident::IdentStr;
 use roc_region::all::Region;
 use snafu::OptionExt;
@@ -207,7 +207,7 @@ lazy_static! {
 #[derive(Debug, Default)]
 pub struct Interns {
     pub module_ids: ModuleIds,
-    pub all_ident_ids: MutMap<ModuleId, IdentIds>,
+    pub all_ident_ids: IdentIdsByModule,
 }
 
 impl Interns {
@@ -249,7 +249,7 @@ impl Interns {
 }
 
 pub fn get_module_ident_ids<'a>(
-    all_ident_ids: &'a MutMap<ModuleId, IdentIds>,
+    all_ident_ids: &'a IdentIdsByModule,
     module_id: &ModuleId,
 ) -> ModuleResult<&'a IdentIds> {
     all_ident_ids
@@ -261,7 +261,7 @@ pub fn get_module_ident_ids<'a>(
 }
 
 pub fn get_module_ident_ids_mut<'a>(
-    all_ident_ids: &'a mut MutMap<ModuleId, IdentIds>,
+    all_ident_ids: &'a mut IdentIdsByModule,
     module_id: &ModuleId,
 ) -> ModuleResult<&'a mut IdentIds> {
     all_ident_ids
@@ -697,6 +697,35 @@ impl IdentIds {
     }
 }
 
+#[derive(Debug, Default)]
+pub struct IdentIdsByModule(VecMap<ModuleId, IdentIds>);
+
+impl IdentIdsByModule {
+    pub fn get_or_insert(&mut self, module_id: ModuleId) -> &mut IdentIds {
+        self.0.get_or_insert(module_id, IdentIds::default)
+    }
+
+    pub fn get_mut(&mut self, key: &ModuleId) -> Option<&mut IdentIds> {
+        self.0.get_mut(key)
+    }
+
+    pub fn get(&self, key: &ModuleId) -> Option<&IdentIds> {
+        self.0.get(key)
+    }
+
+    pub fn insert(&mut self, key: ModuleId, value: IdentIds) -> Option<IdentIds> {
+        self.0.insert(key, value)
+    }
+
+    pub fn keys(&self) -> impl Iterator<Item = &ModuleId> {
+        self.0.keys()
+    }
+
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+}
+
 // BUILTINS
 
 const fn offset_helper<const N: usize>(mut array: [u32; N]) -> [u32; N] {
@@ -778,8 +807,8 @@ macro_rules! define_builtins {
         num_modules: $total:literal
     } => {
         impl IdentIds {
-            pub fn exposed_builtins(extra_capacity: usize) -> MutMap<ModuleId, IdentIds> {
-                let mut exposed_idents_by_module = HashMap::with_capacity_and_hasher(extra_capacity + $total, default_hasher());
+            pub fn exposed_builtins(extra_capacity: usize) -> IdentIdsByModule {
+                let mut exposed_idents_by_module = VecMap::with_capacity(extra_capacity + $total);
 
                 $(
                     debug_assert!(!exposed_idents_by_module.contains_key(&ModuleId($module_id)), r"Error setting up Builtins: when setting up module {} {:?} - the module ID {} is already present in the map. Check the map for duplicate module IDs!", $module_id, $module_name, $module_id);
@@ -838,7 +867,7 @@ macro_rules! define_builtins {
 
                 debug_assert!(exposed_idents_by_module.len() == $total, "Error setting up Builtins: `total:` is set to the wrong amount. It was set to {} but {} modules were set up.", $total, exposed_idents_by_module.len());
 
-                exposed_idents_by_module
+                IdentIdsByModule(exposed_idents_by_module)
             }
         }
 
diff --git a/docs/src/lib.rs b/docs/src/lib.rs
index a2c01973c7..965fc7480f 100644
--- a/docs/src/lib.rs
+++ b/docs/src/lib.rs
@@ -6,13 +6,12 @@ use html::mark_node_to_html;
 use roc_can::scope::Scope;
 use roc_code_markup::markup::nodes::MarkupNode;
 use roc_code_markup::slow_pool::SlowPool;
-use roc_collections::all::MutMap;
 use roc_highlight::highlight_parser::{highlight_defs, highlight_expr};
 use roc_load::docs::DocEntry::DocDef;
 use roc_load::docs::{DocEntry, TypeAnnotation};
 use roc_load::docs::{ModuleDocumentation, RecordField};
 use roc_load::{LoadedModule, LoadingProblem};
-use roc_module::symbol::{IdentIds, Interns, ModuleId};
+use roc_module::symbol::{IdentIdsByModule, Interns, ModuleId};
 use roc_parse::ident::{parse_ident, Ident};
 use roc_parse::state::State;
 use roc_region::all::Region;
@@ -711,7 +710,7 @@ struct DocUrl {
 fn doc_url<'a>(
     home: ModuleId,
     exposed_values: &[&str],
-    dep_idents: &MutMap<ModuleId, IdentIds>,
+    dep_idents: &IdentIdsByModule,
     scope: &Scope,
     interns: &'a Interns,
     mut module_name: &'a str,