diff --git a/Cargo.lock b/Cargo.lock
index 1ce9784ff3..0ceea578ec 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3273,7 +3273,6 @@ dependencies = [
  "morphic_lib",
  "roc_collections",
  "roc_debug_flags",
- "roc_intern",
  "roc_module",
  "roc_mono",
 ]
@@ -3404,7 +3403,6 @@ dependencies = [
  "roc_fmt",
  "roc_gen_llvm",
  "roc_glue",
- "roc_intern",
  "roc_linker",
  "roc_load",
  "roc_module",
@@ -3621,7 +3619,6 @@ dependencies = [
  "roc_can",
  "roc_collections",
  "roc_error_macros",
- "roc_intern",
  "roc_module",
  "roc_mono",
  "roc_parse",
@@ -3647,7 +3644,6 @@ dependencies = [
  "roc_collections",
  "roc_debug_flags",
  "roc_error_macros",
- "roc_intern",
  "roc_module",
  "roc_mono",
  "roc_region",
@@ -3665,7 +3661,6 @@ dependencies = [
  "roc_builtins",
  "roc_collections",
  "roc_error_macros",
- "roc_intern",
  "roc_module",
  "roc_mono",
  "roc_std",
@@ -3689,7 +3684,6 @@ dependencies = [
  "roc_can",
  "roc_collections",
  "roc_error_macros",
- "roc_intern",
  "roc_load",
  "roc_module",
  "roc_mono",
@@ -3718,14 +3712,6 @@ dependencies = [
 name = "roc_ident"
 version = "0.0.1"
 
-[[package]]
-name = "roc_intern"
-version = "0.0.1"
-dependencies = [
- "parking_lot 0.12.1",
- "roc_collections",
-]
-
 [[package]]
 name = "roc_late_solve"
 version = "0.0.1"
@@ -3799,7 +3785,6 @@ dependencies = [
  "roc_derive",
  "roc_derive_key",
  "roc_error_macros",
- "roc_intern",
  "roc_late_solve",
  "roc_module",
  "roc_mono",
@@ -3839,6 +3824,7 @@ dependencies = [
  "bitvec 1.0.1",
  "bumpalo",
  "hashbrown 0.12.3",
+ "parking_lot 0.12.1",
  "roc_builtins",
  "roc_can",
  "roc_collections",
@@ -3847,7 +3833,6 @@ dependencies = [
  "roc_derive_key",
  "roc_error_macros",
  "roc_exhaustive",
- "roc_intern",
  "roc_late_solve",
  "roc_module",
  "roc_problem",
@@ -3928,7 +3913,6 @@ dependencies = [
  "roc_builtins",
  "roc_collections",
  "roc_gen_llvm",
- "roc_intern",
  "roc_load",
  "roc_module",
  "roc_mono",
@@ -3954,7 +3938,6 @@ dependencies = [
  "roc_can",
  "roc_collections",
  "roc_fmt",
- "roc_intern",
  "roc_load",
  "roc_module",
  "roc_mono",
@@ -3984,7 +3967,6 @@ dependencies = [
  "roc_collections",
  "roc_error_macros",
  "roc_gen_llvm",
- "roc_intern",
  "roc_load",
  "roc_module",
  "roc_mono",
diff --git a/crates/cli/Cargo.toml b/crates/cli/Cargo.toml
index 7e68d415da..ddc7c62344 100644
--- a/crates/cli/Cargo.toml
+++ b/crates/cli/Cargo.toml
@@ -63,7 +63,6 @@ roc_editor = { path = "../editor", optional = true }
 roc_linker = { path = "../linker" }
 roc_repl_cli = { path = "../repl_cli", optional = true }
 roc_tracing = { path = "../tracing" }
-roc_intern = { path = "../compiler/intern" }
 roc_gen_llvm = {path = "../compiler/gen_llvm"}
 roc_wasm_interp = { path = "../wasm_interp", optional = true }
 
diff --git a/crates/compiler/alias_analysis/Cargo.toml b/crates/compiler/alias_analysis/Cargo.toml
index 82e5f69671..3b2abd0000 100644
--- a/crates/compiler/alias_analysis/Cargo.toml
+++ b/crates/compiler/alias_analysis/Cargo.toml
@@ -8,7 +8,6 @@ version = "0.0.1"
 [dependencies]
 morphic_lib = {path = "../../vendor/morphic_lib"}
 roc_collections = {path = "../collections"}
-roc_intern = {path = "../intern"}
 roc_module = {path = "../module"}
 roc_mono = {path = "../mono"}
 roc_debug_flags = {path = "../debug_flags"}
diff --git a/crates/compiler/alias_analysis/src/lib.rs b/crates/compiler/alias_analysis/src/lib.rs
index a47ff74445..000982887f 100644
--- a/crates/compiler/alias_analysis/src/lib.rs
+++ b/crates/compiler/alias_analysis/src/lib.rs
@@ -6,7 +6,6 @@ use morphic_lib::{
     TypeDefBuilder, TypeId, TypeName, UpdateModeVar, ValueId,
 };
 use roc_collections::all::{MutMap, MutSet};
-use roc_intern::Interner;
 use roc_module::low_level::LowLevel;
 use roc_module::symbol::Symbol;
 
@@ -15,7 +14,8 @@ use roc_mono::ir::{
     Literal, ModifyRc, OptLevel, Proc, ProcLayout, SingleEntryPoint, Stmt,
 };
 use roc_mono::layout::{
-    Builtin, FieldOrderHash, Layout, Niche, RawFunctionLayout, STLayoutInterner, UnionLayout,
+    Builtin, FieldOrderHash, Layout, LayoutInterner, Niche, RawFunctionLayout, STLayoutInterner,
+    UnionLayout,
 };
 
 // just using one module for now
diff --git a/crates/compiler/gen_dev/Cargo.toml b/crates/compiler/gen_dev/Cargo.toml
index efb194e282..5225d9f3c5 100644
--- a/crates/compiler/gen_dev/Cargo.toml
+++ b/crates/compiler/gen_dev/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2021"
 
 [dependencies]
 roc_collections = { path = "../collections" }
-roc_intern = { path = "../intern" }
 roc_region = { path = "../region" }
 roc_module = { path = "../module" }
 roc_problem = { path = "../problem" }
diff --git a/crates/compiler/gen_llvm/Cargo.toml b/crates/compiler/gen_llvm/Cargo.toml
index 73e556cad0..af3bf91a16 100644
--- a/crates/compiler/gen_llvm/Cargo.toml
+++ b/crates/compiler/gen_llvm/Cargo.toml
@@ -9,7 +9,6 @@ edition = "2021"
 [dependencies]
 roc_alias_analysis = { path = "../alias_analysis" }
 roc_collections = { path = "../collections" }
-roc_intern = { path = "../intern" }
 roc_module = { path = "../module" }
 roc_builtins = { path = "../builtins" }
 roc_error_macros = { path = "../../error_macros" }
diff --git a/crates/compiler/gen_llvm/src/llvm/build.rs b/crates/compiler/gen_llvm/src/llvm/build.rs
index a0b18f3b56..2431b17753 100644
--- a/crates/compiler/gen_llvm/src/llvm/build.rs
+++ b/crates/compiler/gen_llvm/src/llvm/build.rs
@@ -38,15 +38,14 @@ use roc_debug_flags::dbg_do;
 #[cfg(debug_assertions)]
 use roc_debug_flags::ROC_PRINT_LLVM_FN_VERIFICATION;
 use roc_error_macros::internal_error;
-use roc_intern::Interner;
 use roc_module::symbol::{Interns, ModuleId, Symbol};
 use roc_mono::ir::{
     BranchInfo, CallType, CrashTag, EntryPoint, JoinPointId, ListLiteralElement, ModifyRc,
     OptLevel, ProcLayout, SingleEntryPoint,
 };
 use roc_mono::layout::{
-    Builtin, LambdaName, LambdaSet, Layout, LayoutIds, Niche, RawFunctionLayout, STLayoutInterner,
-    TagIdIntType, UnionLayout,
+    Builtin, LambdaName, LambdaSet, Layout, LayoutIds, LayoutInterner, Niche, RawFunctionLayout,
+    STLayoutInterner, TagIdIntType, UnionLayout,
 };
 use roc_std::RocDec;
 use roc_target::{PtrWidth, TargetInfo};
diff --git a/crates/compiler/gen_llvm/src/llvm/build_list.rs b/crates/compiler/gen_llvm/src/llvm/build_list.rs
index 483ba10428..1d4f7f4180 100644
--- a/crates/compiler/gen_llvm/src/llvm/build_list.rs
+++ b/crates/compiler/gen_llvm/src/llvm/build_list.rs
@@ -10,9 +10,8 @@ use inkwell::values::{BasicValueEnum, FunctionValue, IntValue, PointerValue, Str
 use inkwell::{AddressSpace, IntPredicate};
 use morphic_lib::UpdateMode;
 use roc_builtins::bitcode;
-use roc_intern::Interner;
 use roc_module::symbol::Symbol;
-use roc_mono::layout::{Builtin, InLayout, Layout, LayoutIds, STLayoutInterner};
+use roc_mono::layout::{Builtin, InLayout, Layout, LayoutIds, LayoutInterner, STLayoutInterner};
 
 use super::bitcode::{call_list_bitcode_fn, BitcodeReturns};
 use super::build::{
diff --git a/crates/compiler/gen_llvm/src/llvm/compare.rs b/crates/compiler/gen_llvm/src/llvm/compare.rs
index 0870c4f2ff..7ca474b719 100644
--- a/crates/compiler/gen_llvm/src/llvm/compare.rs
+++ b/crates/compiler/gen_llvm/src/llvm/compare.rs
@@ -12,9 +12,10 @@ use inkwell::values::{
 use inkwell::{AddressSpace, FloatPredicate, IntPredicate};
 use roc_builtins::bitcode;
 use roc_builtins::bitcode::{FloatWidth, IntWidth};
-use roc_intern::Interner;
 use roc_module::symbol::Symbol;
-use roc_mono::layout::{Builtin, InLayout, Layout, LayoutIds, STLayoutInterner, UnionLayout};
+use roc_mono::layout::{
+    Builtin, InLayout, Layout, LayoutIds, LayoutInterner, STLayoutInterner, UnionLayout,
+};
 
 use super::build::{load_roc_value, use_roc_value, BuilderExt};
 use super::convert::argument_type_from_union_layout;
diff --git a/crates/compiler/gen_llvm/src/llvm/convert.rs b/crates/compiler/gen_llvm/src/llvm/convert.rs
index 70d7a15fbd..869bef03d8 100644
--- a/crates/compiler/gen_llvm/src/llvm/convert.rs
+++ b/crates/compiler/gen_llvm/src/llvm/convert.rs
@@ -5,8 +5,9 @@ use inkwell::types::{BasicType, BasicTypeEnum, FloatType, IntType, StructType};
 use inkwell::values::StructValue;
 use inkwell::AddressSpace;
 use roc_builtins::bitcode::{FloatWidth, IntWidth};
-use roc_intern::Interner;
-use roc_mono::layout::{round_up_to_alignment, Builtin, Layout, STLayoutInterner, UnionLayout};
+use roc_mono::layout::{
+    round_up_to_alignment, Builtin, Layout, LayoutInterner, STLayoutInterner, UnionLayout,
+};
 use roc_target::TargetInfo;
 
 fn basic_type_from_record<'a, 'ctx, 'env>(
diff --git a/crates/compiler/gen_llvm/src/llvm/expect.rs b/crates/compiler/gen_llvm/src/llvm/expect.rs
index 2fd769f482..4dc3f2cf3e 100644
--- a/crates/compiler/gen_llvm/src/llvm/expect.rs
+++ b/crates/compiler/gen_llvm/src/llvm/expect.rs
@@ -9,10 +9,9 @@ use inkwell::types::{BasicMetadataTypeEnum, BasicType, BasicTypeEnum};
 use inkwell::values::{BasicValueEnum, FunctionValue, IntValue, PointerValue};
 use inkwell::AddressSpace;
 use roc_builtins::bitcode;
-use roc_intern::Interner;
 use roc_module::symbol::Symbol;
 use roc_mono::ir::LookupType;
-use roc_mono::layout::{Builtin, Layout, LayoutIds, STLayoutInterner, UnionLayout};
+use roc_mono::layout::{Builtin, Layout, LayoutIds, LayoutInterner, STLayoutInterner, UnionLayout};
 use roc_region::all::Region;
 
 use super::build::BuilderExt;
diff --git a/crates/compiler/gen_llvm/src/llvm/lowlevel.rs b/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
index 25941b6fc6..63bf733840 100644
--- a/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
+++ b/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
@@ -9,11 +9,10 @@ use inkwell::{
 use morphic_lib::{FuncSpec, UpdateMode};
 use roc_builtins::bitcode::{self, FloatWidth, IntWidth};
 use roc_error_macros::internal_error;
-use roc_intern::Interner;
 use roc_module::{low_level::LowLevel, symbol::Symbol};
 use roc_mono::{
     ir::HigherOrderLowLevel,
-    layout::{Builtin, LambdaSet, Layout, LayoutIds, STLayoutInterner},
+    layout::{Builtin, LambdaSet, Layout, LayoutIds, LayoutInterner, STLayoutInterner},
 };
 use roc_target::PtrWidth;
 
diff --git a/crates/compiler/gen_llvm/src/llvm/refcounting.rs b/crates/compiler/gen_llvm/src/llvm/refcounting.rs
index 6425e91ee2..ba05daeb40 100644
--- a/crates/compiler/gen_llvm/src/llvm/refcounting.rs
+++ b/crates/compiler/gen_llvm/src/llvm/refcounting.rs
@@ -15,10 +15,11 @@ use inkwell::values::{
     BasicValue, BasicValueEnum, FunctionValue, IntValue, PointerValue, StructValue,
 };
 use inkwell::{AddressSpace, IntPredicate};
-use roc_intern::Interner;
 use roc_module::symbol::Interns;
 use roc_module::symbol::Symbol;
-use roc_mono::layout::{Builtin, InLayout, Layout, LayoutIds, STLayoutInterner, UnionLayout};
+use roc_mono::layout::{
+    Builtin, InLayout, Layout, LayoutIds, LayoutInterner, STLayoutInterner, UnionLayout,
+};
 
 use super::build::{cast_if_necessary_for_opaque_recursive_pointers, load_roc_value, FunctionSpec};
 use super::convert::{argument_type_from_layout, argument_type_from_union_layout};
diff --git a/crates/compiler/gen_wasm/Cargo.toml b/crates/compiler/gen_wasm/Cargo.toml
index f3b487ead9..b96de60b50 100644
--- a/crates/compiler/gen_wasm/Cargo.toml
+++ b/crates/compiler/gen_wasm/Cargo.toml
@@ -9,7 +9,6 @@ description = "Provides the WASM backend to generate Roc binaries."
 [dependencies]
 roc_builtins = { path = "../builtins" }
 roc_collections = { path = "../collections" }
-roc_intern = { path = "../intern" }
 roc_module = { path = "../module" }
 roc_mono = { path = "../mono" }
 roc_target = { path = "../roc_target" }
diff --git a/crates/compiler/gen_wasm/src/backend.rs b/crates/compiler/gen_wasm/src/backend.rs
index a236ed2bdd..4c39e79b54 100644
--- a/crates/compiler/gen_wasm/src/backend.rs
+++ b/crates/compiler/gen_wasm/src/backend.rs
@@ -4,7 +4,6 @@ use bumpalo::collections::{String, Vec};
 use roc_builtins::bitcode::{FloatWidth, IntWidth};
 use roc_collections::all::MutMap;
 use roc_error_macros::internal_error;
-use roc_intern::Interner;
 use roc_module::low_level::{LowLevel, LowLevelWrapperType};
 use roc_module::symbol::{Interns, Symbol};
 use roc_mono::code_gen_help::{CodeGenHelp, HelperOp, REFCOUNT_MAX};
@@ -12,7 +11,9 @@ use roc_mono::ir::{
     BranchInfo, CallType, CrashTag, Expr, JoinPointId, ListLiteralElement, Literal, ModifyRc,
     Param, Proc, ProcLayout, Stmt,
 };
-use roc_mono::layout::{Builtin, Layout, LayoutIds, STLayoutInterner, TagIdIntType, UnionLayout};
+use roc_mono::layout::{
+    Builtin, Layout, LayoutIds, LayoutInterner, STLayoutInterner, TagIdIntType, UnionLayout,
+};
 use roc_std::RocDec;
 
 use roc_wasm_module::linking::{DataSymbol, WasmObjectSymbol};
diff --git a/crates/compiler/gen_wasm/src/low_level.rs b/crates/compiler/gen_wasm/src/low_level.rs
index d1e0d02caf..c1c93a8491 100644
--- a/crates/compiler/gen_wasm/src/low_level.rs
+++ b/crates/compiler/gen_wasm/src/low_level.rs
@@ -2,12 +2,11 @@ use bumpalo::collections::Vec;
 use bumpalo::Bump;
 use roc_builtins::bitcode::{self, FloatWidth, IntWidth};
 use roc_error_macros::internal_error;
-use roc_intern::Interner;
 use roc_module::low_level::LowLevel;
 use roc_module::symbol::Symbol;
 use roc_mono::code_gen_help::HelperOp;
 use roc_mono::ir::{HigherOrderLowLevel, PassedFunction, ProcLayout};
-use roc_mono::layout::{Builtin, FieldOrderHash, InLayout, Layout, UnionLayout};
+use roc_mono::layout::{Builtin, FieldOrderHash, InLayout, Layout, LayoutInterner, UnionLayout};
 use roc_mono::low_level::HigherOrder;
 
 use crate::backend::{ProcLookupData, ProcSource, WasmBackend};
diff --git a/crates/compiler/intern/Cargo.toml b/crates/compiler/intern/Cargo.toml
deleted file mode 100644
index 2d9623d0e2..0000000000
--- a/crates/compiler/intern/Cargo.toml
+++ /dev/null
@@ -1,11 +0,0 @@
-[package]
-name = "roc_intern"
-version = "0.0.1"
-authors = ["The Roc Contributors"]
-license = "UPL-1.0"
-edition = "2021"
-description = "Provides generic interners for concurrent and single-thread use cases."
-
-[dependencies]
-roc_collections = { path = "../collections" }
-parking_lot = "0.12"
diff --git a/crates/compiler/intern/src/lib.rs b/crates/compiler/intern/src/lib.rs
deleted file mode 100644
index c7640233d3..0000000000
--- a/crates/compiler/intern/src/lib.rs
+++ /dev/null
@@ -1,253 +0,0 @@
-//! Generic interners for concurrent and single-thread use cases.
-
-use std::{
-    cell::RefCell,
-    hash::{BuildHasher, Hash, Hasher},
-    marker::PhantomData,
-    sync::Arc,
-};
-
-use parking_lot::{Mutex, RwLock};
-use roc_collections::{default_hasher, BumpMap};
-
-/// An interned value.
-///
-/// When possible, prefer comparing/hashing on the [Interned] representation of a value, rather
-/// than the value itself.
-#[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
-pub struct Interned<T>(usize, std::marker::PhantomData<T>);
-impl<T> Clone for Interned<T> {
-    fn clone(&self) -> Self {
-        Self(self.0, Default::default())
-    }
-}
-
-impl<T> Copy for Interned<T> {}
-
-impl<T> Interned<T> {
-    /// # Safety
-    ///
-    /// The index is not guaranteed to exist. Use this only when creating an interner with constant
-    /// indices, with the variant that `insert` returns a monotonically increasing index.
-    ///
-    /// For example:
-    ///
-    /// ```ignore(illustrative)
-    /// let reserved_interned = Interned::from_reserved_index(0);
-    /// let interner = GlobalInterner::with_capacity(1);
-    /// let inserted = interner.insert("something");
-    /// assert_eq!(reserved_interned, inserted);
-    /// ```
-    pub const unsafe fn from_reserved_index(index: usize) -> Self {
-        Self(index, PhantomData)
-    }
-}
-
-/// A concurrent interner, suitable for usage between threads.
-///
-/// The interner does not currently maintain its own arena; you will have to supply
-/// values-to-be-interned as allocated in an independent arena.
-///
-/// If you need a concurrent global interner, you'll likely want each thread to take a
-/// [ThreadLocalInterner] via [GlobalInterner::fork], for caching purposes.
-///
-/// Originally derived from https://gist.github.com/matklad/44ba1a5a6168bc0c26c995131c007907;
-/// thank you, Aleksey!
-#[derive(Debug)]
-pub struct GlobalInterner<'a, K> {
-    map: Mutex<BumpMap<&'a K, Interned<K>>>,
-    vec: RwLock<Vec<&'a K>>,
-}
-
-/// A derivative of a [GlobalInterner] interner that provides caching desirable for
-/// thread-local workloads. The only way to get a [ThreadLocalInterner] is via
-/// [GlobalInterner::fork].
-///
-/// All values interned into a [ThreadLocalInterner] are made available in its parent
-/// [GlobalInterner], making this suitable for global sharing of interned values.
-///
-/// Originally derived from https://gist.github.com/matklad/44ba1a5a6168bc0c26c995131c007907;
-/// thank you, Aleksey!
-#[derive(Debug)]
-pub struct ThreadLocalInterner<'a, K> {
-    parent: Arc<GlobalInterner<'a, K>>,
-    map: BumpMap<&'a K, Interned<K>>,
-    /// Cache of interned values from the parent for local access.
-    vec: RefCell<Vec<Option<&'a K>>>,
-}
-
-/// A single-threaded interner, with no concurrency properties.
-///
-/// The only way to construct such an interner is to collapse a shared [GlobalInterner] into
-/// a [SingleThreadedInterner], via [GlobalInterner::unwrap].
-#[derive(Debug)]
-pub struct SingleThreadedInterner<'a, K> {
-    map: BumpMap<&'a K, Interned<K>>,
-    vec: Vec<&'a K>,
-}
-
-/// Generic hasher for a value, to be used by all interners.
-///
-/// This uses the [default_hasher], so interner maps should also rely on [default_hasher].
-fn hash<V: Hash>(val: V) -> u64 {
-    let mut state = roc_collections::all::BuildHasher::default().build_hasher();
-    val.hash(&mut state);
-    state.finish()
-}
-
-pub trait Interner<'a, K: Hash + Eq> {
-    /// Interns a value, returning its interned representation.
-    /// If the value has been interned before, the old interned representation will be re-used.
-    ///
-    /// Note that the provided value must be allocated into an arena of your choosing, but which
-    /// must live at least as long as the interner lives.
-    // TODO: we should consider maintaining our own arena in the interner, to avoid redundant
-    // allocations when values already have interned representations.
-    fn insert(&mut self, value: &'a K) -> Interned<K>;
-
-    /// Retrieves a value from the interner.
-    fn get(&self, key: Interned<K>) -> &'a K;
-}
-
-impl<'a, K: Hash + Eq> GlobalInterner<'a, K> {
-    /// Creates a new global interner with the given capacity.
-    pub fn with_capacity(cap: usize) -> Arc<GlobalInterner<'a, K>> {
-        let map: BumpMap<&'a K, Interned<K>> =
-            BumpMap::with_capacity_and_hasher(cap, default_hasher());
-
-        Arc::new(GlobalInterner {
-            map: Mutex::new(map),
-            vec: RwLock::new(Vec::with_capacity(cap)),
-        })
-    }
-
-    /// Creates a derivative [ThreadLocalInterner] pointing back to this global interner.
-    pub fn fork(self: &Arc<GlobalInterner<'a, K>>) -> ThreadLocalInterner<'a, K> {
-        ThreadLocalInterner {
-            parent: Arc::clone(self),
-            map: Default::default(),
-            vec: Default::default(),
-        }
-    }
-
-    /// Collapses a shared [GlobalInterner] into a [SingleThreadedInterner].
-    ///
-    /// Returns an [Err] with `self` if there are outstanding references to the [GlobalInterner].
-    pub fn unwrap(
-        self: Arc<GlobalInterner<'a, K>>,
-    ) -> Result<SingleThreadedInterner<'a, K>, Arc<Self>> {
-        let GlobalInterner { map, vec } = Arc::try_unwrap(self)?;
-        let map = Mutex::into_inner(map);
-        let vec = RwLock::into_inner(vec);
-        Ok(SingleThreadedInterner { map, vec })
-    }
-
-    /// Interns a value with a pre-computed hash.
-    /// Prefer calling this when possible, especially from [ThreadLocalInterner], to avoid
-    /// re-computing hashes.
-    fn insert_hashed(&self, value: &'a K, hash: u64) -> Interned<K> {
-        let mut map = self.map.lock();
-        let (_, interned) = map
-            .raw_entry_mut()
-            .from_key_hashed_nocheck(hash, &value)
-            .or_insert_with(|| {
-                let mut vec = self.vec.write();
-                let interned = Interned(vec.len(), Default::default());
-                vec.push(value);
-                (value, interned)
-            });
-        *interned
-    }
-
-    fn get(&self, interned: Interned<K>) -> &'a K {
-        let Interned(index, _) = interned;
-        self.vec.read()[index]
-    }
-
-    pub fn is_empty(&self) -> bool {
-        self.vec.read().is_empty()
-    }
-}
-
-impl<'a, K: Hash + Eq> ThreadLocalInterner<'a, K> {
-    /// Records an interned value in thread-specific storage, for faster access on lookups.
-    fn record(&self, key: &'a K, interned: Interned<K>) {
-        let mut vec = self.vec.borrow_mut();
-        let len = vec.len().max(interned.0 + 1);
-        vec.resize(len, None);
-        vec[interned.0] = Some(key);
-    }
-}
-
-impl<'a, K: Hash + Eq> Interner<'a, K> for ThreadLocalInterner<'a, K> {
-    fn insert(&mut self, value: &'a K) -> Interned<K> {
-        let global = &*self.parent;
-        let hash = hash(value);
-        let (&mut value, &mut interned) = self
-            .map
-            .raw_entry_mut()
-            .from_key_hashed_nocheck(hash, &value)
-            .or_insert_with(|| {
-                let interned = global.insert_hashed(value, hash);
-                (value, interned)
-            });
-        self.record(value, interned);
-        interned
-    }
-
-    fn get(&self, key: Interned<K>) -> &'a K {
-        if let Some(Some(value)) = self.vec.borrow().get(key.0) {
-            return value;
-        }
-        let value = self.parent.get(key);
-        self.record(value, key);
-        value
-    }
-}
-
-impl<'a, K> SingleThreadedInterner<'a, K> {
-    /// Creates a new single threaded interner with the given capacity.
-    pub fn with_capacity(cap: usize) -> Self {
-        Self {
-            map: BumpMap::with_capacity_and_hasher(cap, default_hasher()),
-            vec: Vec::with_capacity(cap),
-        }
-    }
-
-    /// Promotes the [SingleThreadedInterner] back to a [GlobalInterner].
-    ///
-    /// You should *only* use this if you need to go from a single-threaded to a concurrent context,
-    /// or in a case where you explicitly need access to [ThreadLocalInterner]s.
-    pub fn into_global(self) -> Arc<GlobalInterner<'a, K>> {
-        let SingleThreadedInterner { map, vec } = self;
-        Arc::new(GlobalInterner {
-            map: Mutex::new(map),
-            vec: RwLock::new(vec),
-        })
-    }
-
-    pub fn is_empty(&self) -> bool {
-        self.vec.is_empty()
-    }
-}
-
-impl<'a, K: Hash + Eq> Interner<'a, K> for SingleThreadedInterner<'a, K> {
-    fn insert(&mut self, value: &'a K) -> Interned<K> {
-        let hash = hash(value);
-        let (_, interned) = self
-            .map
-            .raw_entry_mut()
-            .from_key_hashed_nocheck(hash, value)
-            .or_insert_with(|| {
-                let interned = Interned(self.vec.len(), Default::default());
-                self.vec.push(value);
-                (value, interned)
-            });
-        *interned
-    }
-
-    fn get(&self, key: Interned<K>) -> &'a K {
-        let Interned(index, _) = key;
-        self.vec[index]
-    }
-}
diff --git a/crates/compiler/load_internal/Cargo.toml b/crates/compiler/load_internal/Cargo.toml
index 2e2a6f147f..a52d997f93 100644
--- a/crates/compiler/load_internal/Cargo.toml
+++ b/crates/compiler/load_internal/Cargo.toml
@@ -24,7 +24,6 @@ roc_solve = { path = "../solve" }
 roc_solve_problem = { path = "../solve_problem" }
 roc_late_solve = { path = "../late_solve" }
 roc_mono = { path = "../mono" }
-roc_intern = { path = "../intern" }
 roc_target = { path = "../roc_target" }
 roc_tracing = { path = "../../tracing" }
 roc_packaging = { path = "../../packaging" }
diff --git a/crates/compiler/mono/Cargo.toml b/crates/compiler/mono/Cargo.toml
index 86dbabe0dd..73ce78d7a0 100644
--- a/crates/compiler/mono/Cargo.toml
+++ b/crates/compiler/mono/Cargo.toml
@@ -15,7 +15,6 @@ roc_types = { path = "../types" }
 roc_can = { path = "../can" }
 roc_derive_key = { path = "../derive_key" }
 roc_derive = { path = "../derive" }
-roc_intern = { path = "../intern" }
 roc_late_solve = { path = "../late_solve" }
 roc_std = { path = "../../roc_std" }
 roc_problem = { path = "../problem" }
@@ -30,3 +29,4 @@ bumpalo.workspace = true
 hashbrown.workspace = true
 static_assertions.workspace = true
 bitvec.workspace = true
+parking_lot.workspace = true
diff --git a/crates/compiler/mono/src/code_gen_help/equality.rs b/crates/compiler/mono/src/code_gen_help/equality.rs
index 7c6cb5ff14..0cca077512 100644
--- a/crates/compiler/mono/src/code_gen_help/equality.rs
+++ b/crates/compiler/mono/src/code_gen_help/equality.rs
@@ -1,12 +1,13 @@
 use bumpalo::collections::vec::Vec;
-use roc_intern::Interner;
 use roc_module::low_level::LowLevel;
 use roc_module::symbol::{IdentIds, Symbol};
 
 use crate::ir::{
     BranchInfo, Call, CallType, Expr, JoinPointId, Literal, Param, Stmt, UpdateModeId,
 };
-use crate::layout::{Builtin, InLayout, Layout, STLayoutInterner, TagIdIntType, UnionLayout};
+use crate::layout::{
+    Builtin, InLayout, Layout, LayoutInterner, STLayoutInterner, TagIdIntType, UnionLayout,
+};
 
 use super::{let_lowlevel, CodeGenHelp, Context, LAYOUT_BOOL};
 
diff --git a/crates/compiler/mono/src/code_gen_help/mod.rs b/crates/compiler/mono/src/code_gen_help/mod.rs
index a0c43a8988..35f49d2e7b 100644
--- a/crates/compiler/mono/src/code_gen_help/mod.rs
+++ b/crates/compiler/mono/src/code_gen_help/mod.rs
@@ -1,6 +1,5 @@
 use bumpalo::collections::vec::Vec;
 use bumpalo::Bump;
-use roc_intern::Interner;
 use roc_module::low_level::LowLevel;
 use roc_module::symbol::{IdentIds, ModuleId, Symbol};
 use roc_target::TargetInfo;
@@ -9,7 +8,9 @@ use crate::ir::{
     Call, CallSpecId, CallType, Expr, HostExposedLayouts, JoinPointId, ModifyRc, Proc, ProcLayout,
     SelfRecursive, Stmt, UpdateModeId,
 };
-use crate::layout::{Builtin, LambdaName, Layout, Niche, STLayoutInterner, UnionLayout};
+use crate::layout::{
+    Builtin, LambdaName, Layout, LayoutInterner, Niche, STLayoutInterner, UnionLayout,
+};
 
 mod equality;
 mod refcount;
diff --git a/crates/compiler/mono/src/code_gen_help/refcount.rs b/crates/compiler/mono/src/code_gen_help/refcount.rs
index 701d146014..897fb863fc 100644
--- a/crates/compiler/mono/src/code_gen_help/refcount.rs
+++ b/crates/compiler/mono/src/code_gen_help/refcount.rs
@@ -2,7 +2,6 @@
 
 use bumpalo::collections::vec::Vec;
 use roc_builtins::bitcode::IntWidth;
-use roc_intern::Interner;
 use roc_module::low_level::{LowLevel, LowLevel::*};
 use roc_module::symbol::{IdentIds, Symbol};
 use roc_target::PtrWidth;
diff --git a/crates/compiler/mono/src/debug/checker.rs b/crates/compiler/mono/src/debug/checker.rs
index dfaa98336b..e6823bb8b4 100644
--- a/crates/compiler/mono/src/debug/checker.rs
+++ b/crates/compiler/mono/src/debug/checker.rs
@@ -2,7 +2,6 @@
 
 use bumpalo::Bump;
 use roc_collections::{MutMap, VecMap, VecSet};
-use roc_intern::Interner;
 use roc_module::symbol::Symbol;
 
 use crate::{
@@ -10,7 +9,9 @@ use crate::{
         Call, CallSpecId, CallType, Expr, HigherOrderLowLevel, JoinPointId, ListLiteralElement,
         ModifyRc, Param, Proc, ProcLayout, Stmt,
     },
-    layout::{Builtin, LambdaSet, Layout, STLayoutInterner, TagIdIntType, UnionLayout},
+    layout::{
+        Builtin, LambdaSet, Layout, LayoutInterner, STLayoutInterner, TagIdIntType, UnionLayout,
+    },
 };
 
 pub enum UseKind {
diff --git a/crates/compiler/mono/src/decision_tree.rs b/crates/compiler/mono/src/decision_tree.rs
index 0b9f692a65..4c60bc57e1 100644
--- a/crates/compiler/mono/src/decision_tree.rs
+++ b/crates/compiler/mono/src/decision_tree.rs
@@ -2,12 +2,13 @@ use crate::ir::{
     build_list_index_probe, BranchInfo, Call, CallType, DestructType, Env, Expr, JoinPointId,
     ListIndex, Literal, Param, Pattern, Procs, Stmt,
 };
-use crate::layout::{Builtin, Layout, LayoutCache, TLLayoutInterner, TagIdIntType, UnionLayout};
+use crate::layout::{
+    Builtin, Layout, LayoutCache, LayoutInterner, TLLayoutInterner, TagIdIntType, UnionLayout,
+};
 use roc_builtins::bitcode::{FloatWidth, IntWidth};
 use roc_collections::all::{MutMap, MutSet};
 use roc_error_macros::internal_error;
 use roc_exhaustive::{Ctor, CtorName, ListArity, RenderAs, TagId, Union};
-use roc_intern::Interner;
 use roc_module::ident::TagName;
 use roc_module::low_level::LowLevel;
 use roc_module::symbol::Symbol;
diff --git a/crates/compiler/mono/src/layout.rs b/crates/compiler/mono/src/layout.rs
index 64dcd19484..2591320706 100644
--- a/crates/compiler/mono/src/layout.rs
+++ b/crates/compiler/mono/src/layout.rs
@@ -5,7 +5,6 @@ use bumpalo::Bump;
 use roc_builtins::bitcode::{FloatWidth, IntWidth};
 use roc_collections::all::{default_hasher, FnvMap, MutMap};
 use roc_error_macros::{internal_error, todo_abilities};
-use roc_intern::Interner;
 use roc_module::ident::{Lowercase, TagName};
 use roc_module::symbol::{Interns, Symbol};
 use roc_problem::can::RuntimeError;
@@ -23,7 +22,9 @@ use std::hash::{Hash, Hasher};
 use ven_pretty::{DocAllocator, DocBuilder};
 
 mod intern;
-pub use intern::{GlobalLayoutInterner, LayoutInterner, STLayoutInterner, TLLayoutInterner};
+pub use intern::{
+    GlobalLayoutInterner, InLayout, LayoutInterner, STLayoutInterner, TLLayoutInterner,
+};
 
 // if your changes cause this number to go down, great!
 // please change it to the lower number.
@@ -661,10 +662,6 @@ impl FieldOrderHash {
     }
 }
 
-/// An interned layout.
-// One day I would like to take over `LayoutId` as the name here, but that is currently used elsewhere.
-pub type InLayout<'a> = roc_intern::Interned<Layout<'a>>;
-
 /// Types for code gen must be monomorphic. No type variables allowed!
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub enum Layout<'a> {
diff --git a/crates/compiler/mono/src/layout/intern.rs b/crates/compiler/mono/src/layout/intern.rs
index d7b6d28b7d..4881e96bd7 100644
--- a/crates/compiler/mono/src/layout/intern.rs
+++ b/crates/compiler/mono/src/layout/intern.rs
@@ -1,25 +1,33 @@
-use std::{marker::PhantomData, sync::Arc};
+use std::{
+    cell::RefCell,
+    hash::{BuildHasher, Hasher},
+    marker::PhantomData,
+    sync::Arc,
+};
 
+use parking_lot::{Mutex, RwLock};
 use roc_builtins::bitcode::{FloatWidth, IntWidth};
-use roc_intern::{GlobalInterner, Interned, Interner, SingleThreadedInterner, ThreadLocalInterner};
+use roc_collections::{default_hasher, BumpMap};
 use roc_target::TargetInfo;
 
 use super::{Builtin, Layout};
 
-pub struct InternedLayouts(PhantomData<()>);
+#[allow(unused)] // for now
+pub struct InLayouts(PhantomData<()>);
 
 macro_rules! cache_interned_layouts {
     ($($i:literal, $name:ident, $layout:expr)*; $total_constants:literal) => {
-        impl InternedLayouts {
+        impl InLayouts {
             $(
-            pub const $name: Interned<Layout<'static>> = unsafe { Interned::from_reserved_index($i) };
+            #[allow(unused)] // for now
+            pub const $name: InLayout<'static> = unsafe { InLayout::from_reserved_index($i) };
             )*
         }
 
         fn fill_reserved_layouts<'a>(interner: &mut STLayoutInterner<'a>) {
-            assert!(interner.0.is_empty());
+            assert!(interner.is_empty());
             $(
-            interner.0.insert(&$layout);
+            interner.insert(&$layout);
             )*
         }
 
@@ -59,8 +67,9 @@ cache_interned_layouts! {
     ; 16
 }
 
-impl InternedLayouts {
-    pub const fn from_int_width(w: IntWidth) -> Interned<Layout<'static>> {
+impl InLayouts {
+    #[allow(unused)] // for now
+    pub const fn from_int_width(w: IntWidth) -> InLayout<'static> {
         match w {
             IntWidth::U8 => Self::U8,
             IntWidth::U16 => Self::U16,
@@ -74,7 +83,8 @@ impl InternedLayouts {
             IntWidth::I128 => Self::I128,
         }
     }
-    pub const fn from_float_width(w: FloatWidth) -> Interned<Layout<'static>> {
+    #[allow(unused)] // for now
+    pub const fn from_float_width(w: FloatWidth) -> InLayout<'static> {
         match w {
             FloatWidth::F32 => Self::F32,
             FloatWidth::F64 => Self::F64,
@@ -82,63 +92,248 @@ impl InternedLayouts {
     }
 }
 
-pub trait LayoutInterner<'a>: Interner<'a, Layout<'a>> + Sized {
-    fn alignment_bytes(&self, target_info: TargetInfo, layout: Interned<Layout<'a>>) -> u32 {
+pub trait LayoutInterner<'a>: Sized {
+    /// Interns a value, returning its interned representation.
+    /// If the value has been interned before, the old interned representation will be re-used.
+    ///
+    /// Note that the provided value must be allocated into an arena of your choosing, but which
+    /// must live at least as long as the interner lives.
+    // TODO: we should consider maintaining our own arena in the interner, to avoid redundant
+    // allocations when values already have interned representations.
+    fn insert(&mut self, value: &'a Layout<'a>) -> InLayout<'a>;
+
+    /// Retrieves a value from the interner.
+    fn get(&self, key: InLayout<'a>) -> &'a Layout<'a>;
+
+    fn alignment_bytes(&self, target_info: TargetInfo, layout: InLayout<'a>) -> u32 {
         self.get(layout).alignment_bytes(self, target_info)
     }
 }
 
+/// An interned layout.
+///
+/// When possible, prefer comparing/hashing on the [InLayout] representation of a value, rather
+/// than the value itself.
+#[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct InLayout<'a>(usize, std::marker::PhantomData<&'a ()>);
+impl<'a> Clone for InLayout<'a> {
+    fn clone(&self) -> Self {
+        Self(self.0, Default::default())
+    }
+}
+
+impl<'a> Copy for InLayout<'a> {}
+
+impl<'a> InLayout<'a> {
+    /// # Safety
+    ///
+    /// The index is not guaranteed to exist. Use this only when creating an interner with constant
+    /// indices, with the variant that `insert` returns a monotonically increasing index.
+    ///
+    /// For example:
+    ///
+    /// ```ignore(illustrative)
+    /// let reserved_interned = InLayout::from_reserved_index(0);
+    /// let interner = GlobalLayoutInterner::with_capacity(1);
+    /// let inserted = interner.insert("something");
+    /// assert_eq!(reserved_interned, inserted);
+    /// ```
+    const unsafe fn from_reserved_index(index: usize) -> Self {
+        Self(index, PhantomData)
+    }
+}
+
+/// A concurrent interner, suitable for usage between threads.
+///
+/// The interner does not currently maintain its own arena; you will have to supply
+/// values-to-be-interned as allocated in an independent arena.
+///
+/// If you need a concurrent global interner, you'll likely want each thread to take a
+/// [TLLayoutInterner] via [GlobalLayoutInterner::fork], for caching purposes.
+///
+/// Originally derived from https://gist.github.com/matklad/44ba1a5a6168bc0c26c995131c007907;
+/// thank you, Aleksey!
 #[derive(Debug)]
-pub struct GlobalLayoutInterner<'a>(Arc<GlobalInterner<'a, Layout<'a>>>);
+pub struct GlobalLayoutInterner<'a>(Arc<GlobalLayoutInternerInner<'a>>);
+
 #[derive(Debug)]
-pub struct TLLayoutInterner<'a>(ThreadLocalInterner<'a, Layout<'a>>);
+struct GlobalLayoutInternerInner<'a> {
+    map: Mutex<BumpMap<&'a Layout<'a>, InLayout<'a>>>,
+    vec: RwLock<Vec<&'a Layout<'a>>>,
+}
+
+/// A derivative of a [GlobalLayoutInterner] interner that provides caching desirable for
+/// thread-local workloads. The only way to get a [TLLayoutInterner] is via
+/// [GlobalLayoutInterner::fork].
+///
+/// All values interned into a [TLLayoutInterner] are made available in its parent
+/// [GlobalLayoutInterner], making this suitable for global sharing of interned values.
+///
+/// Originally derived from https://gist.github.com/matklad/44ba1a5a6168bc0c26c995131c007907;
+/// thank you, Aleksey!
 #[derive(Debug)]
-pub struct STLayoutInterner<'a>(SingleThreadedInterner<'a, Layout<'a>>);
+pub struct TLLayoutInterner<'a> {
+    parent: GlobalLayoutInterner<'a>,
+    map: BumpMap<&'a Layout<'a>, InLayout<'a>>,
+    /// Cache of interned values from the parent for local access.
+    vec: RefCell<Vec<Option<&'a Layout<'a>>>>,
+}
+
+/// A single-threaded interner, with no concurrency properties.
+///
+/// The only way to construct such an interner is to collapse a shared [GlobalLayoutInterner] into
+/// a [STLayoutInterner], via [GlobalLayoutInterner::unwrap].
+#[derive(Debug)]
+pub struct STLayoutInterner<'a> {
+    map: BumpMap<&'a Layout<'a>, InLayout<'a>>,
+    vec: Vec<&'a Layout<'a>>,
+}
+
+/// Generic hasher for a value, to be used by all interners.
+///
+/// This uses the [default_hasher], so interner maps should also rely on [default_hasher].
+fn hash<V: std::hash::Hash>(val: V) -> u64 {
+    let mut state = roc_collections::all::BuildHasher::default().build_hasher();
+    val.hash(&mut state);
+    state.finish()
+}
 
 impl<'a> GlobalLayoutInterner<'a> {
-    pub fn with_capacity(capacity: usize) -> Self {
-        STLayoutInterner::with_capacity(capacity).into_global()
+    /// Creates a new global interner with the given capacity.
+    pub fn with_capacity(cap: usize) -> Self {
+        STLayoutInterner::with_capacity(cap).into_global()
     }
+
+    /// Creates a derivative [TLLayoutInterner] pointing back to this global interner.
     pub fn fork(&self) -> TLLayoutInterner<'a> {
-        TLLayoutInterner(self.0.fork())
-    }
-    pub fn unwrap(self) -> Result<STLayoutInterner<'a>, Self> {
-        match self.0.unwrap() {
-            Ok(st) => Ok(STLayoutInterner(st)),
-            Err(global) => Err(Self(global)),
+        TLLayoutInterner {
+            parent: Self(Arc::clone(&self.0)),
+            map: Default::default(),
+            vec: Default::default(),
         }
     }
+
+    /// Collapses a shared [GlobalLayoutInterner] into a [STLayoutInterner].
+    ///
+    /// Returns an [Err] with `self` if there are outstanding references to the [GlobalLayoutInterner].
+    pub fn unwrap(self) -> Result<STLayoutInterner<'a>, Self> {
+        let GlobalLayoutInternerInner { map, vec } = match Arc::try_unwrap(self.0) {
+            Ok(inner) => inner,
+            Err(li) => return Err(Self(li)),
+        };
+        let map = Mutex::into_inner(map);
+        let vec = RwLock::into_inner(vec);
+        Ok(STLayoutInterner { map, vec })
+    }
+
+    /// Interns a value with a pre-computed hash.
+    /// Prefer calling this when possible, especially from [TLLayoutInterner], to avoid
+    /// re-computing hashes.
+    fn insert_hashed(&self, value: &'a Layout<'a>, hash: u64) -> InLayout<'a> {
+        let mut map = self.0.map.lock();
+        let (_, interned) = map
+            .raw_entry_mut()
+            .from_key_hashed_nocheck(hash, &value)
+            .or_insert_with(|| {
+                let mut vec = self.0.vec.write();
+                let interned = InLayout(vec.len(), Default::default());
+                vec.push(value);
+                (value, interned)
+            });
+        *interned
+    }
+
+    fn get(&self, interned: InLayout<'a>) -> &'a Layout<'a> {
+        let InLayout(index, _) = interned;
+        self.0.vec.read()[index]
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.vec.read().is_empty()
+    }
+}
+
+impl<'a> TLLayoutInterner<'a> {
+    /// Records an interned value in thread-specific storage, for faster access on lookups.
+    fn record(&self, key: &'a Layout<'a>, interned: InLayout<'a>) {
+        let mut vec = self.vec.borrow_mut();
+        let len = vec.len().max(interned.0 + 1);
+        vec.resize(len, None);
+        vec[interned.0] = Some(key);
+    }
+}
+
+impl<'a> LayoutInterner<'a> for TLLayoutInterner<'a> {
+    fn insert(&mut self, value: &'a Layout<'a>) -> InLayout<'a> {
+        let global = &self.parent;
+        let hash = hash(value);
+        let (&mut value, &mut interned) = self
+            .map
+            .raw_entry_mut()
+            .from_key_hashed_nocheck(hash, &value)
+            .or_insert_with(|| {
+                let interned = global.insert_hashed(value, hash);
+                (value, interned)
+            });
+        self.record(value, interned);
+        interned
+    }
+
+    fn get(&self, key: InLayout<'a>) -> &'a Layout<'a> {
+        if let Some(Some(value)) = self.vec.borrow().get(key.0) {
+            return value;
+        }
+        let value = self.parent.get(key);
+        self.record(value, key);
+        value
+    }
 }
 
 impl<'a> STLayoutInterner<'a> {
-    pub fn with_capacity(capacity: usize) -> Self {
-        let mut interner = Self(SingleThreadedInterner::with_capacity(capacity));
+    /// Creates a new single threaded interner with the given capacity.
+    pub fn with_capacity(cap: usize) -> Self {
+        let mut interner = Self {
+            map: BumpMap::with_capacity_and_hasher(cap, default_hasher()),
+            vec: Vec::with_capacity(cap),
+        };
         fill_reserved_layouts(&mut interner);
         interner
     }
+
+    /// Promotes the [STLayoutInterner] back to a [GlobalLayoutInterner].
+    ///
+    /// You should *only* use this if you need to go from a single-threaded to a concurrent context,
+    /// or in a case where you explicitly need access to [TLLayoutInterner]s.
     pub fn into_global(self) -> GlobalLayoutInterner<'a> {
-        GlobalLayoutInterner(self.0.into_global())
+        let STLayoutInterner { map, vec } = self;
+        GlobalLayoutInterner(Arc::new(GlobalLayoutInternerInner {
+            map: Mutex::new(map),
+            vec: RwLock::new(vec),
+        }))
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.vec.is_empty()
     }
 }
 
-impl<'a> Interner<'a, Layout<'a>> for TLLayoutInterner<'a> {
-    fn insert(&mut self, value: &'a Layout<'a>) -> Interned<Layout<'a>> {
-        self.0.insert(value)
+impl<'a> LayoutInterner<'a> for STLayoutInterner<'a> {
+    fn insert(&mut self, value: &'a Layout<'a>) -> InLayout<'a> {
+        let hash = hash(value);
+        let (_, interned) = self
+            .map
+            .raw_entry_mut()
+            .from_key_hashed_nocheck(hash, value)
+            .or_insert_with(|| {
+                let interned = InLayout(self.vec.len(), Default::default());
+                self.vec.push(value);
+                (value, interned)
+            });
+        *interned
     }
 
-    fn get(&self, key: Interned<Layout<'a>>) -> &'a Layout<'a> {
-        self.0.get(key)
+    fn get(&self, key: InLayout<'a>) -> &'a Layout<'a> {
+        let InLayout(index, _) = key;
+        self.vec[index]
     }
 }
-impl<'a> LayoutInterner<'a> for TLLayoutInterner<'a> {}
-
-impl<'a> Interner<'a, Layout<'a>> for STLayoutInterner<'a> {
-    fn insert(&mut self, value: &'a Layout<'a>) -> Interned<Layout<'a>> {
-        self.0.insert(value)
-    }
-
-    fn get(&self, key: Interned<Layout<'a>>) -> &'a Layout<'a> {
-        self.0.get(key)
-    }
-}
-impl<'a> LayoutInterner<'a> for STLayoutInterner<'a> {}
diff --git a/crates/glue/Cargo.toml b/crates/glue/Cargo.toml
index 4b750ef0b9..90564f6864 100644
--- a/crates/glue/Cargo.toml
+++ b/crates/glue/Cargo.toml
@@ -9,7 +9,6 @@ description = "Generates code needed for platform hosts to communicate with Roc
 [dependencies]
 roc_std = { path = "../roc_std"}
 roc_can = { path = "../compiler/can" }
-roc_intern = { path = "../compiler/intern" }
 roc_mono = { path = "../compiler/mono" }
 roc_load = { path = "../compiler/load" }
 roc_reporting = { path = "../reporting" }
diff --git a/crates/repl_cli/Cargo.toml b/crates/repl_cli/Cargo.toml
index 7425e6bcd3..518953831a 100644
--- a/crates/repl_cli/Cargo.toml
+++ b/crates/repl_cli/Cargo.toml
@@ -29,7 +29,6 @@ roc_build = {path = "../compiler/build"}
 roc_builtins = {path = "../compiler/builtins"}
 roc_collections = {path = "../compiler/collections"}
 roc_gen_llvm = {path = "../compiler/gen_llvm"}
-roc_intern = {path = "../compiler/intern"}
 roc_load = {path = "../compiler/load"}
 roc_mono = {path = "../compiler/mono"}
 roc_parse = {path = "../compiler/parse"}
diff --git a/crates/repl_eval/Cargo.toml b/crates/repl_eval/Cargo.toml
index d98083b459..d1ffdf93a1 100644
--- a/crates/repl_eval/Cargo.toml
+++ b/crates/repl_eval/Cargo.toml
@@ -15,7 +15,6 @@ roc_builtins = {path = "../compiler/builtins"}
 roc_can = {path = "../compiler/can"}
 roc_collections = {path = "../compiler/collections"}
 roc_fmt = {path = "../compiler/fmt"}
-roc_intern = {path = "../compiler/intern"}
 roc_load = {path = "../compiler/load"}
 roc_module = {path = "../compiler/module"}
 roc_mono = {path = "../compiler/mono"}
diff --git a/crates/repl_eval/src/eval.rs b/crates/repl_eval/src/eval.rs
index 6346f1c7d9..65b952acc6 100644
--- a/crates/repl_eval/src/eval.rs
+++ b/crates/repl_eval/src/eval.rs
@@ -1,6 +1,5 @@
 use bumpalo::collections::Vec;
 use bumpalo::Bump;
-use roc_intern::Interner;
 use roc_types::types::AliasKind;
 use std::cmp::{max_by_key, min_by_key};
 
@@ -11,8 +10,8 @@ use roc_module::ident::TagName;
 use roc_module::symbol::{Interns, ModuleId, Symbol};
 use roc_mono::ir::ProcLayout;
 use roc_mono::layout::{
-    self, union_sorted_tags_pub, Builtin, InLayout, Layout, LayoutCache, TLLayoutInterner,
-    UnionLayout, UnionVariant, WrappedVariant,
+    self, union_sorted_tags_pub, Builtin, InLayout, Layout, LayoutCache, LayoutInterner,
+    TLLayoutInterner, UnionLayout, UnionVariant, WrappedVariant,
 };
 use roc_parse::ast::{AssignedField, Collection, Expr, Pattern, StrLiteral};
 use roc_region::all::{Loc, Region};
diff --git a/crates/repl_expect/Cargo.toml b/crates/repl_expect/Cargo.toml
index 760de2913c..bae087b61c 100644
--- a/crates/repl_expect/Cargo.toml
+++ b/crates/repl_expect/Cargo.toml
@@ -17,7 +17,6 @@ inkwell.workspace = true
 roc_builtins = {path = "../compiler/builtins"}
 roc_can = {path = "../compiler/can"}
 roc_collections = {path = "../compiler/collections"}
-roc_intern = {path = "../compiler/intern"}
 roc_load = {path = "../compiler/load"}
 roc_mono = {path = "../compiler/mono"}
 roc_parse = {path = "../compiler/parse"}