diff --git a/compiler/gen/src/llvm/bitcode.rs b/compiler/gen/src/llvm/bitcode.rs
index f038a6c47e..b80f51375e 100644
--- a/compiler/gen/src/llvm/bitcode.rs
+++ b/compiler/gen/src/llvm/bitcode.rs
@@ -122,16 +122,13 @@ fn build_transform_caller_help<'a, 'ctx, 'env>(
         set_name(*argument, name.ident_string(&env.interns));
     }
 
-    let closure_type =
-        basic_type_from_layout(env.arena, env.context, function_layout, env.ptr_bytes)
-            .ptr_type(AddressSpace::Generic);
+    let closure_type = basic_type_from_layout(env, function_layout).ptr_type(AddressSpace::Generic);
 
     let mut arguments_cast =
         bumpalo::collections::Vec::with_capacity_in(arguments.len(), env.arena);
 
     for (argument_ptr, layout) in arguments.iter().zip(argument_layouts) {
-        let basic_type = basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes)
-            .ptr_type(AddressSpace::Generic);
+        let basic_type = basic_type_from_layout(env, layout).ptr_type(AddressSpace::Generic);
 
         let argument_cast = env
             .builder
@@ -278,8 +275,7 @@ pub fn build_rc_wrapper<'a, 'ctx, 'env>(
 
             set_name(value_ptr.into(), Symbol::ARG_1.ident_string(&env.interns));
 
-            let value_type = basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes)
-                .ptr_type(AddressSpace::Generic);
+            let value_type = basic_type_from_layout(env, layout).ptr_type(AddressSpace::Generic);
 
             let value_cast = env
                 .builder
@@ -352,8 +348,7 @@ pub fn build_eq_wrapper<'a, 'ctx, 'env>(
             set_name(value_ptr1.into(), Symbol::ARG_1.ident_string(&env.interns));
             set_name(value_ptr2.into(), Symbol::ARG_2.ident_string(&env.interns));
 
-            let value_type = basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes)
-                .ptr_type(AddressSpace::Generic);
+            let value_type = basic_type_from_layout(env, layout).ptr_type(AddressSpace::Generic);
 
             let value_cast1 = env
                 .builder
@@ -434,7 +429,7 @@ pub fn build_compare_wrapper<'a, 'ctx, 'env>(
             set_name(value_ptr1.into(), Symbol::ARG_2.ident_string(&env.interns));
             set_name(value_ptr2.into(), Symbol::ARG_3.ident_string(&env.interns));
 
-            let value_type = basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes);
+            let value_type = basic_type_from_layout(env, layout);
             let function_type = env
                 .context
                 .i8_type()
diff --git a/compiler/gen/src/llvm/build.rs b/compiler/gen/src/llvm/build.rs
index 5b50fec240..d39906df19 100644
--- a/compiler/gen/src/llvm/build.rs
+++ b/compiler/gen/src/llvm/build.rs
@@ -896,12 +896,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                 // The layout of the struct expects them to be dropped!
                 let (field_expr, field_layout) = load_symbol_and_layout(scope, symbol);
                 if !field_layout.is_dropped_because_empty() {
-                    field_types.push(basic_type_from_layout(
-                        env.arena,
-                        env.context,
-                        &field_layout,
-                        env.ptr_bytes,
-                    ));
+                    field_types.push(basic_type_from_layout(env, &field_layout));
 
                     field_vals.push(field_expr);
                 }
@@ -953,12 +948,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             for field_symbol in it {
                 let (val, field_layout) = load_symbol_and_layout(scope, field_symbol);
                 if !field_layout.is_dropped_because_empty() {
-                    let field_type = basic_type_from_layout(
-                        env.arena,
-                        env.context,
-                        &field_layout,
-                        env.ptr_bytes,
-                    );
+                    let field_type = basic_type_from_layout(env, &field_layout);
 
                     field_types.push(field_type);
                     field_vals.push(val);
@@ -1000,7 +990,6 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             let tag_layout = Layout::Union(UnionLayout::NonRecursive(fields));
 
             debug_assert!(*union_size > 1);
-            let ptr_size = env.ptr_bytes;
 
             let ctx = env.context;
             let builder = env.builder;
@@ -1018,8 +1007,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                 // Zero-sized fields have no runtime representation.
                 // The layout of the struct expects them to be dropped!
                 if !tag_field_layout.is_dropped_because_empty() {
-                    let field_type =
-                        basic_type_from_layout(env.arena, env.context, tag_field_layout, ptr_size);
+                    let field_type = basic_type_from_layout(env, tag_field_layout);
 
                     field_types.push(field_type);
 
@@ -1076,8 +1064,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             // This tricks comes from
             // https://github.com/raviqqe/ssf/blob/bc32aae68940d5bddf5984128e85af75ca4f4686/ssf-llvm/src/expression_compiler.rs#L116
 
-            let internal_type =
-                basic_type_from_layout(env.arena, env.context, &tag_layout, env.ptr_bytes);
+            let internal_type = basic_type_from_layout(env, &tag_layout);
 
             cast_tag_to_block_of_memory(builder, struct_val.into_struct_value(), internal_type)
         }
@@ -1091,7 +1078,6 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             let tag_layout = Layout::Union(UnionLayout::NonRecursive(fields));
 
             debug_assert!(*union_size > 1);
-            let ptr_size = env.ptr_bytes;
 
             let ctx = env.context;
             let builder = env.builder;
@@ -1109,8 +1095,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                 // Zero-sized fields have no runtime representation.
                 // The layout of the struct expects them to be dropped!
                 if !tag_field_layout.is_dropped_because_empty() {
-                    let field_type =
-                        basic_type_from_layout(env.arena, env.context, tag_field_layout, ptr_size);
+                    let field_type = basic_type_from_layout(env, tag_field_layout);
 
                     field_types.push(field_type);
 
@@ -1172,7 +1157,6 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             let struct_layout =
                 Layout::Union(UnionLayout::NonRecursive(env.arena.alloc([*fields])));
 
-            let ptr_size = env.ptr_bytes;
             let ctx = env.context;
             let builder = env.builder;
 
@@ -1187,8 +1171,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                 // Zero-sized fields have no runtime representation.
                 // The layout of the struct expects them to be dropped!
                 if !tag_field_layout.is_dropped_because_empty() {
-                    let field_type =
-                        basic_type_from_layout(env.arena, env.context, tag_field_layout, ptr_size);
+                    let field_type = basic_type_from_layout(env, tag_field_layout);
 
                     field_types.push(field_type);
 
@@ -1247,8 +1230,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             ..
         } => {
             let tag_layout = Layout::Union(UnionLayout::NonRecursive(fields));
-            let tag_struct_type =
-                basic_type_from_layout(env.arena, env.context, &tag_layout, env.ptr_bytes);
+            let tag_struct_type = basic_type_from_layout(env, &tag_layout);
             if *tag_id == *nullable_id as u8 {
                 let output_type = tag_struct_type.ptr_type(AddressSpace::Generic);
 
@@ -1256,7 +1238,6 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             }
 
             debug_assert!(*union_size > 1);
-            let ptr_size = env.ptr_bytes;
 
             let ctx = env.context;
             let builder = env.builder;
@@ -1281,8 +1262,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                 // Zero-sized fields have no runtime representation.
                 // The layout of the struct expects them to be dropped!
                 if !tag_field_layout.is_dropped_because_empty() {
-                    let field_type =
-                        basic_type_from_layout(env.arena, env.context, tag_field_layout, ptr_size);
+                    let field_type = basic_type_from_layout(env, tag_field_layout);
 
                     field_types.push(field_type);
 
@@ -1359,7 +1339,6 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             debug_assert!(!arguments.is_empty());
 
             debug_assert!(*union_size == 2);
-            let ptr_size = env.ptr_bytes;
 
             let ctx = env.context;
             let builder = env.builder;
@@ -1382,8 +1361,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                 // Zero-sized fields have no runtime representation.
                 // The layout of the struct expects them to be dropped!
                 if !tag_field_layout.is_dropped_because_empty() {
-                    let field_type =
-                        basic_type_from_layout(env.arena, env.context, tag_field_layout, ptr_size);
+                    let field_type = basic_type_from_layout(env, tag_field_layout);
 
                     field_types.push(field_type);
 
@@ -1484,12 +1462,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                     Layout::Union(UnionLayout::NonNullableUnwrapped(fields)),
                 ) => {
                     let struct_layout = Layout::Struct(fields);
-                    let struct_type = basic_type_from_layout(
-                        env.arena,
-                        env.context,
-                        &struct_layout,
-                        env.ptr_bytes,
-                    );
+                    let struct_type = basic_type_from_layout(env, &struct_layout);
 
                     let cast_argument = env
                         .builder
@@ -1531,11 +1504,9 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             // Determine types, assumes the descriminant is in the field layouts
             let num_fields = field_layouts.len();
             let mut field_types = Vec::with_capacity_in(num_fields, env.arena);
-            let ptr_bytes = env.ptr_bytes;
 
             for field_layout in field_layouts.iter() {
-                let field_type =
-                    basic_type_from_layout(env.arena, env.context, &field_layout, ptr_bytes);
+                let field_type = basic_type_from_layout(env, &field_layout);
                 field_types.push(field_type);
             }
 
@@ -1727,7 +1698,7 @@ fn lookup_at_index_ptr<'a, 'ctx, 'env>(
         // a pointer to the block of memory representation
         builder.build_bitcast(
             result,
-            basic_type_from_layout(env.arena, env.context, structure_layout, env.ptr_bytes),
+            basic_type_from_layout(env, structure_layout),
             "cast_rec_pointer_lookup_at_index_ptr",
         )
     } else {
@@ -1773,7 +1744,7 @@ pub fn allocate_with_refcount_help<'a, 'ctx, 'env>(
     let builder = env.builder;
     let ctx = env.context;
 
-    let value_type = basic_type_from_layout(env.arena, ctx, layout, env.ptr_bytes);
+    let value_type = basic_type_from_layout(env, layout);
     let len_type = env.ptr_int();
 
     let extra_bytes = layout.alignment_bytes(env.ptr_bytes).max(env.ptr_bytes);
@@ -2189,8 +2160,7 @@ pub fn build_exp_stmt<'a, 'ctx, 'env>(
             cond_layout,
             cond_symbol,
         } => {
-            let ret_type =
-                basic_type_from_layout(env.arena, env.context, &ret_layout, env.ptr_bytes);
+            let ret_type = basic_type_from_layout(env, &ret_layout);
 
             let switch_args = SwitchArgsIr {
                 cond_layout: *cond_layout,
@@ -2214,8 +2184,7 @@ pub fn build_exp_stmt<'a, 'ctx, 'env>(
             let mut joinpoint_args = Vec::with_capacity_in(parameters.len(), env.arena);
 
             for param in parameters.iter() {
-                let btype =
-                    basic_type_from_layout(env.arena, env.context, &param.layout, env.ptr_bytes);
+                let btype = basic_type_from_layout(env, &param.layout);
                 joinpoint_args.push(create_entry_block_alloca(
                     env,
                     parent,
@@ -3077,7 +3046,6 @@ pub fn build_proc_header<'a, 'ctx, 'env>(
 ) -> FunctionValue<'ctx> {
     let args = proc.args;
     let arena = env.arena;
-    let context = &env.context;
 
     let fn_name = layout_ids
         .get(symbol, layout)
@@ -3114,11 +3082,11 @@ pub fn build_proc_header<'a, 'ctx, 'env>(
         }
     }
 
-    let ret_type = basic_type_from_layout(arena, context, &proc.ret_layout, env.ptr_bytes);
+    let ret_type = basic_type_from_layout(env, &proc.ret_layout);
     let mut arg_basic_types = Vec::with_capacity_in(args.len(), arena);
 
     for (layout, _) in args.iter() {
-        let arg_type = basic_type_from_layout(arena, env.context, &layout, env.ptr_bytes);
+        let arg_type = basic_type_from_layout(env, &layout);
 
         arg_basic_types.push(arg_type);
     }
@@ -3167,7 +3135,7 @@ pub fn build_closure_caller<'a, 'ctx, 'env>(
     let mut argument_types = Vec::with_capacity_in(arguments.len() + 3, env.arena);
 
     for layout in arguments {
-        let arg_type = basic_type_from_layout(arena, context, layout, env.ptr_bytes);
+        let arg_type = basic_type_from_layout(env, layout);
         let arg_ptr_type = arg_type.ptr_type(AddressSpace::Generic);
 
         argument_types.push(arg_ptr_type.into());
@@ -3178,23 +3146,18 @@ pub fn build_closure_caller<'a, 'ctx, 'env>(
             ClosureLayout::extend_function_layout(arena, arguments, *closure, result);
 
         // this is already a (function) pointer type
-        basic_type_from_layout(arena, context, &function_layout, env.ptr_bytes)
+        basic_type_from_layout(env, &function_layout)
     };
     argument_types.push(function_pointer_type);
 
     let closure_argument_type = {
-        let basic_type = basic_type_from_layout(
-            arena,
-            context,
-            &closure.as_block_of_memory_layout(),
-            env.ptr_bytes,
-        );
+        let basic_type = basic_type_from_layout(env, &closure.as_block_of_memory_layout());
 
         basic_type.ptr_type(AddressSpace::Generic)
     };
     argument_types.push(closure_argument_type.into());
 
-    let result_type = basic_type_from_layout(arena, context, result, env.ptr_bytes);
+    let result_type = basic_type_from_layout(env, result);
 
     let roc_call_result_type =
         context.struct_type(&[context.i64_type().into(), result_type], false);
@@ -3263,7 +3226,6 @@ pub fn build_function_caller<'a, 'ctx, 'env>(
 ) {
     use inkwell::types::BasicType;
 
-    let arena = env.arena;
     let context = &env.context;
     let builder = env.builder;
 
@@ -3279,7 +3241,7 @@ pub fn build_function_caller<'a, 'ctx, 'env>(
     let mut argument_types = Vec::with_capacity_in(arguments.len() + 3, env.arena);
 
     for layout in arguments {
-        let arg_type = basic_type_from_layout(arena, context, layout, env.ptr_bytes);
+        let arg_type = basic_type_from_layout(env, layout);
         let arg_ptr_type = arg_type.ptr_type(AddressSpace::Generic);
 
         argument_types.push(arg_ptr_type.into());
@@ -3295,19 +3257,18 @@ pub fn build_function_caller<'a, 'ctx, 'env>(
         let function_layout = Layout::FunctionPointer(&args, result);
 
         // this is already a (function) pointer type
-        basic_type_from_layout(arena, context, &function_layout, env.ptr_bytes)
+        basic_type_from_layout(env, &function_layout)
     };
     argument_types.push(function_pointer_type);
 
     let closure_argument_type = {
-        let basic_type =
-            basic_type_from_layout(arena, context, &Layout::Struct(&[]), env.ptr_bytes);
+        let basic_type = basic_type_from_layout(env, &Layout::Struct(&[]));
 
         basic_type.ptr_type(AddressSpace::Generic)
     };
     argument_types.push(closure_argument_type.into());
 
-    let result_type = basic_type_from_layout(arena, context, result, env.ptr_bytes);
+    let result_type = basic_type_from_layout(env, result);
 
     let roc_call_result_type =
         context.struct_type(&[context.i64_type().into(), result_type], false);
@@ -3338,12 +3299,8 @@ pub fn build_function_caller<'a, 'ctx, 'env>(
 
     // let closure_data = context.struct_type(&[], false).const_zero().into();
 
-    let actual_function_type = basic_type_from_layout(
-        arena,
-        context,
-        &Layout::FunctionPointer(arguments, result),
-        env.ptr_bytes,
-    );
+    let actual_function_type =
+        basic_type_from_layout(env, &Layout::FunctionPointer(arguments, result));
 
     let function_ptr = builder
         .build_bitcast(function_ptr, actual_function_type, "cast")
@@ -3387,7 +3344,7 @@ fn build_host_exposed_alias_size<'a, 'ctx, 'env>(
         def_name,
         alias_symbol,
         None,
-        basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes),
+        basic_type_from_layout(env, layout),
     )
 }
 
@@ -4115,8 +4072,7 @@ fn run_low_level<'a, 'ctx, 'env>(
 
             let arg = load_symbol(scope, &args[0]).into_int_value();
 
-            let to = basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes)
-                .into_int_type();
+            let to = basic_type_from_layout(env, layout).into_int_type();
 
             env.builder.build_int_cast(arg, to, "inc_cast").into()
         }
@@ -4455,7 +4411,7 @@ fn build_foreign_symbol_return_result<'a, 'ctx, 'env>(
     for arg in arguments.iter() {
         let (value, layout) = load_symbol_and_layout(scope, arg);
         arg_vals.push(value);
-        let arg_type = basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes);
+        let arg_type = basic_type_from_layout(env, layout);
         debug_assert_eq!(arg_type, value.get_type());
         arg_types.push(arg_type);
     }
@@ -4482,7 +4438,7 @@ fn build_foreign_symbol_write_result_into_ptr<'a, 'ctx, 'env>(
     for arg in arguments.iter() {
         let (value, layout) = load_symbol_and_layout(scope, arg);
         arg_vals.push(value);
-        let arg_type = basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes);
+        let arg_type = basic_type_from_layout(env, layout);
         debug_assert_eq!(arg_type, value.get_type());
         arg_types.push(arg_type);
     }
@@ -4504,7 +4460,7 @@ fn build_foreign_symbol<'a, 'ctx, 'env>(
     ret_layout: &Layout<'a>,
     call_or_invoke: ForeignCallOrInvoke<'a>,
 ) -> BasicValueEnum<'ctx> {
-    let ret_type = basic_type_from_layout(env.arena, env.context, ret_layout, env.ptr_bytes);
+    let ret_type = basic_type_from_layout(env, ret_layout);
     let return_pointer = env.builder.build_alloca(ret_type, "return_value");
 
     // crude approximation of the C calling convention
@@ -4611,9 +4567,8 @@ where
         Layout::Builtin(Builtin::List(MemoryMode::Refcounted, _)) => {
             // no static guarantees, but all is not lost: we can check the refcount
             // if it is one, we hold the final reference, and can mutate it in-place!
-            let ctx = env.context;
 
-            let ret_type = basic_type_from_layout(env.arena, ctx, list_layout, env.ptr_bytes);
+            let ret_type = basic_type_from_layout(env, list_layout);
 
             let refcount_ptr = PointerToRefcount::from_list_wrapper(env, original_wrapper);
             let refcount = refcount_ptr.get_refcount(env);
@@ -5109,7 +5064,7 @@ fn builtin_to_int_type<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
     builtin: &Builtin<'a>,
 ) -> IntType<'ctx> {
-    let result = basic_type_from_builtin(env.arena, env.context, builtin, env.ptr_bytes);
+    let result = basic_type_from_builtin(env, builtin);
     debug_assert!(result.is_int_type());
 
     result.into_int_type()
@@ -5229,10 +5184,7 @@ fn int_abs_with_overflow<'a, 'ctx, 'env>(
         let bits_to_shift = ((arg_layout.stack_size(env.ptr_bytes) as u64) * 8) - 1;
         let shift_val = ctx.i64_type().const_int(bits_to_shift, false);
         let shifted = bd.build_right_shift(arg, shift_val, true, shifted_name);
-        let alloca = bd.build_alloca(
-            basic_type_from_builtin(env.arena, ctx, arg_layout, env.ptr_bytes),
-            "#int_abs_help",
-        );
+        let alloca = bd.build_alloca(basic_type_from_builtin(env, arg_layout), "#int_abs_help");
 
         // shifted = arg >>> 63
         bd.build_store(alloca, shifted);
diff --git a/compiler/gen/src/llvm/build_dict.rs b/compiler/gen/src/llvm/build_dict.rs
index 105dc32643..f7ef5ca3e9 100644
--- a/compiler/gen/src/llvm/build_dict.rs
+++ b/compiler/gen/src/llvm/build_dict.rs
@@ -6,7 +6,7 @@ use crate::llvm::bitcode::{
 use crate::llvm::build::{
     complex_bitcast, load_symbol, load_symbol_and_layout, set_name, Env, Scope,
 };
-use crate::llvm::convert::{self, as_const_zero, basic_type_from_layout, collection};
+use crate::llvm::convert::{as_const_zero, basic_type_from_layout, collection};
 use crate::llvm::refcounting::Mode;
 use inkwell::attributes::{Attribute, AttributeLoc};
 use inkwell::types::BasicType;
@@ -83,12 +83,7 @@ pub fn dict_empty<'a, 'ctx, 'env>(
 
     call_void_bitcode_fn(env, &[result_alloc.into()], &bitcode::DICT_EMPTY);
 
-    let result = env
-        .builder
-        .build_load(result_alloc, "load_result")
-        .into_struct_value();
-
-    zig_dict_to_struct(env, result).into()
+    env.builder.build_load(result_alloc, "load_result")
 }
 
 #[allow(clippy::too_many_arguments)]
@@ -110,8 +105,7 @@ pub fn dict_insert<'a, 'ctx, 'env>(
     let key_ptr = builder.build_alloca(key.get_type(), "key_ptr");
     let value_ptr = builder.build_alloca(value.get_type(), "value_ptr");
 
-    env.builder
-        .build_store(dict_ptr, struct_to_zig_dict(env, dict.into_struct_value()));
+    env.builder.build_store(dict_ptr, dict);
     env.builder.build_store(key_ptr, key);
     env.builder.build_store(value_ptr, value);
 
@@ -152,15 +146,6 @@ pub fn dict_insert<'a, 'ctx, 'env>(
         &bitcode::DICT_INSERT,
     );
 
-    let result_ptr = env
-        .builder
-        .build_bitcast(
-            result_ptr,
-            convert::dict(env.context, env.ptr_bytes).ptr_type(AddressSpace::Generic),
-            "to_roc_dict",
-        )
-        .into_pointer_value();
-
     env.builder.build_load(result_ptr, "load_result")
 }
 
@@ -181,8 +166,7 @@ pub fn dict_remove<'a, 'ctx, 'env>(
     let dict_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
     let key_ptr = builder.build_alloca(key.get_type(), "key_ptr");
 
-    env.builder
-        .build_store(dict_ptr, struct_to_zig_dict(env, dict.into_struct_value()));
+    env.builder.build_store(dict_ptr, dict);
     env.builder.build_store(key_ptr, key);
 
     let key_width = env
@@ -221,15 +205,6 @@ pub fn dict_remove<'a, 'ctx, 'env>(
         &bitcode::DICT_REMOVE,
     );
 
-    let result_ptr = env
-        .builder
-        .build_bitcast(
-            result_ptr,
-            convert::dict(env.context, env.ptr_bytes).ptr_type(AddressSpace::Generic),
-            "to_roc_dict",
-        )
-        .into_pointer_value();
-
     env.builder.build_load(result_ptr, "load_result")
 }
 
@@ -250,8 +225,7 @@ pub fn dict_contains<'a, 'ctx, 'env>(
     let dict_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
     let key_ptr = builder.build_alloca(key.get_type(), "key_ptr");
 
-    env.builder
-        .build_store(dict_ptr, struct_to_zig_dict(env, dict.into_struct_value()));
+    env.builder.build_store(dict_ptr, dict);
     env.builder.build_store(key_ptr, key);
 
     let key_width = env
@@ -300,8 +274,7 @@ pub fn dict_get<'a, 'ctx, 'env>(
     let dict_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
     let key_ptr = builder.build_alloca(key.get_type(), "key_ptr");
 
-    env.builder
-        .build_store(dict_ptr, struct_to_zig_dict(env, dict.into_struct_value()));
+    env.builder.build_store(dict_ptr, dict);
     env.builder.build_store(key_ptr, key);
 
     let key_width = env
@@ -355,7 +328,7 @@ pub fn dict_get<'a, 'ctx, 'env>(
     let if_not_null = env.context.append_basic_block(parent, "if_not_null");
     let done_block = env.context.append_basic_block(parent, "done");
 
-    let value_bt = basic_type_from_layout(env.arena, env.context, value_layout, env.ptr_bytes);
+    let value_bt = basic_type_from_layout(env, value_layout);
     let default = as_const_zero(&value_bt);
 
     env.builder
@@ -411,8 +384,7 @@ pub fn dict_elements_rc<'a, 'ctx, 'env>(
     let zig_dict_type = env.module.get_struct_type("dict.RocDict").unwrap();
 
     let dict_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
-    env.builder
-        .build_store(dict_ptr, struct_to_zig_dict(env, dict.into_struct_value()));
+    env.builder.build_store(dict_ptr, dict);
 
     let key_width = env
         .ptr_int()
@@ -457,8 +429,7 @@ pub fn dict_keys<'a, 'ctx, 'env>(
     let zig_list_type = env.module.get_struct_type("list.RocList").unwrap();
 
     let dict_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
-    env.builder
-        .build_store(dict_ptr, struct_to_zig_dict(env, dict.into_struct_value()));
+    env.builder.build_store(dict_ptr, dict);
 
     let key_width = env
         .ptr_int()
@@ -516,15 +487,8 @@ pub fn dict_union<'a, 'ctx, 'env>(
     let dict1_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
     let dict2_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
 
-    env.builder.build_store(
-        dict1_ptr,
-        struct_to_zig_dict(env, dict1.into_struct_value()),
-    );
-
-    env.builder.build_store(
-        dict2_ptr,
-        struct_to_zig_dict(env, dict2.into_struct_value()),
-    );
+    env.builder.build_store(dict1_ptr, dict1);
+    env.builder.build_store(dict2_ptr, dict2);
 
     let key_width = env
         .ptr_int()
@@ -562,15 +526,6 @@ pub fn dict_union<'a, 'ctx, 'env>(
         &bitcode::DICT_UNION,
     );
 
-    let output_ptr = env
-        .builder
-        .build_bitcast(
-            output_ptr,
-            convert::dict(env.context, env.ptr_bytes).ptr_type(AddressSpace::Generic),
-            "to_roc_dict",
-        )
-        .into_pointer_value();
-
     env.builder.build_load(output_ptr, "load_output_ptr")
 }
 
@@ -631,15 +586,8 @@ fn dict_intersect_or_difference<'a, 'ctx, 'env>(
     let dict1_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
     let dict2_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
 
-    env.builder.build_store(
-        dict1_ptr,
-        struct_to_zig_dict(env, dict1.into_struct_value()),
-    );
-
-    env.builder.build_store(
-        dict2_ptr,
-        struct_to_zig_dict(env, dict2.into_struct_value()),
-    );
+    env.builder.build_store(dict1_ptr, dict1);
+    env.builder.build_store(dict2_ptr, dict2);
 
     let key_width = env
         .ptr_int()
@@ -677,15 +625,6 @@ fn dict_intersect_or_difference<'a, 'ctx, 'env>(
         op,
     );
 
-    let output_ptr = env
-        .builder
-        .build_bitcast(
-            output_ptr,
-            convert::dict(env.context, env.ptr_bytes).ptr_type(AddressSpace::Generic),
-            "to_roc_dict",
-        )
-        .into_pointer_value();
-
     env.builder.build_load(output_ptr, "load_output_ptr")
 }
 
@@ -707,8 +646,7 @@ pub fn dict_walk<'a, 'ctx, 'env>(
     let zig_dict_type = env.module.get_struct_type("dict.RocDict").unwrap();
 
     let dict_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
-    env.builder
-        .build_store(dict_ptr, struct_to_zig_dict(env, dict.into_struct_value()));
+    env.builder.build_store(dict_ptr, dict);
 
     let stepper_ptr = builder.build_alloca(stepper.get_type(), "stepper_ptr");
     env.builder.build_store(stepper_ptr, stepper);
@@ -722,7 +660,7 @@ pub fn dict_walk<'a, 'ctx, 'env>(
     .as_global_value()
     .as_pointer_value();
 
-    let accum_bt = basic_type_from_layout(env.arena, env.context, accum_layout, env.ptr_bytes);
+    let accum_bt = basic_type_from_layout(env, accum_layout);
     let accum_ptr = builder.build_alloca(accum_bt, "accum_ptr");
     env.builder.build_store(accum_ptr, accum);
 
@@ -781,8 +719,7 @@ pub fn dict_values<'a, 'ctx, 'env>(
     let zig_list_type = env.module.get_struct_type("list.RocList").unwrap();
 
     let dict_ptr = builder.build_alloca(zig_dict_type, "dict_ptr");
-    env.builder
-        .build_store(dict_ptr, struct_to_zig_dict(env, dict.into_struct_value()));
+    env.builder.build_store(dict_ptr, dict);
 
     let key_width = env
         .ptr_int()
@@ -833,8 +770,6 @@ pub fn set_from_list<'a, 'ctx, 'env>(
 ) -> BasicValueEnum<'ctx> {
     let builder = env.builder;
 
-    let zig_dict_type = env.module.get_struct_type("dict.RocDict").unwrap();
-
     let list_alloca = builder.build_alloca(list.get_type(), "list_alloca");
     let list_ptr = env.builder.build_bitcast(
         list_alloca,
@@ -850,13 +785,7 @@ pub fn set_from_list<'a, 'ctx, 'env>(
 
     let value_width = env.ptr_int().const_zero();
 
-    let result_alloca =
-        builder.build_alloca(convert::dict(env.context, env.ptr_bytes), "result_alloca");
-    let result_ptr = builder.build_bitcast(
-        result_alloca,
-        zig_dict_type.ptr_type(AddressSpace::Generic),
-        "to_zig_dict",
-    );
+    let result_alloca = builder.build_alloca(zig_dict_type(env), "result_alloca");
 
     let alignment =
         Alignment::from_key_value_layout(key_layout, &Layout::Struct(&[]), env.ptr_bytes);
@@ -878,7 +807,7 @@ pub fn set_from_list<'a, 'ctx, 'env>(
             hash_fn.as_global_value().as_pointer_value().into(),
             eq_fn.as_global_value().as_pointer_value().into(),
             dec_key_fn.as_global_value().as_pointer_value().into(),
-            result_ptr,
+            result_alloca.into(),
         ],
         &bitcode::SET_FROM_LIST,
     );
@@ -929,8 +858,7 @@ fn build_hash_wrapper<'a, 'ctx, 'env>(
             set_name(seed_arg.into(), Symbol::ARG_1.ident_string(&env.interns));
             set_name(value_ptr.into(), Symbol::ARG_2.ident_string(&env.interns));
 
-            let value_type = basic_type_from_layout(env.arena, env.context, layout, env.ptr_bytes)
-                .ptr_type(AddressSpace::Generic);
+            let value_type = basic_type_from_layout(env, layout).ptr_type(AddressSpace::Generic);
 
             let value_cast = env
                 .builder
@@ -968,31 +896,6 @@ fn dict_symbol_to_zig_dict<'a, 'ctx, 'env>(
         .into_struct_value()
 }
 
-fn zig_dict_to_struct<'a, 'ctx, 'env>(
-    env: &Env<'a, 'ctx, 'env>,
-    zig_dict: StructValue<'ctx>,
-) -> StructValue<'ctx> {
-    complex_bitcast(
-        env.builder,
-        zig_dict.into(),
-        crate::llvm::convert::dict(env.context, env.ptr_bytes).into(),
-        "to_zig_dict",
-    )
-    .into_struct_value()
-}
-
-fn struct_to_zig_dict<'a, 'ctx, 'env>(
-    env: &Env<'a, 'ctx, 'env>,
-    struct_dict: StructValue<'ctx>,
-) -> StructValue<'ctx> {
-    // get the RocStr type defined by zig
-    let zig_dict_type = env.module.get_struct_type("dict.RocDict").unwrap();
-
-    complex_bitcast(
-        env.builder,
-        struct_dict.into(),
-        zig_dict_type.into(),
-        "to_zig_dict",
-    )
-    .into_struct_value()
+fn zig_dict_type<'a, 'ctx, 'env>(env: &Env<'a, 'ctx, 'env>) -> inkwell::types::StructType<'ctx> {
+    env.module.get_struct_type("dict.RocDict").unwrap()
 }
diff --git a/compiler/gen/src/llvm/build_hash.rs b/compiler/gen/src/llvm/build_hash.rs
index 3b33bf20d3..95db536a88 100644
--- a/compiler/gen/src/llvm/build_hash.rs
+++ b/compiler/gen/src/llvm/build_hash.rs
@@ -72,7 +72,7 @@ fn build_hash_layout<'a, 'ctx, 'env>(
             WhenRecursive::Loop(union_layout) => {
                 let layout = Layout::Union(union_layout);
 
-                let bt = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+                let bt = basic_type_from_layout(env, &layout);
 
                 // cast the i64 pointer to a pointer to block of memory
                 let field_cast = env
@@ -190,12 +190,9 @@ fn build_hash_struct<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let arena = env.arena;
-
             let seed_type = env.context.i64_type();
 
-            let arg_type =
-                basic_type_from_layout(arena, env.context, &struct_layout, env.ptr_bytes);
+            let arg_type = basic_type_from_layout(env, &struct_layout);
 
             let function_value = crate::llvm::refcounting::build_header_help(
                 env,
@@ -289,12 +286,7 @@ fn hash_struct<'a, 'ctx, 'env>(
                     WhenRecursive::Loop(union_layout) => {
                         let field_layout = Layout::Union(*union_layout);
 
-                        let bt = basic_type_from_layout(
-                            env.arena,
-                            env.context,
-                            &field_layout,
-                            env.ptr_bytes,
-                        );
+                        let bt = basic_type_from_layout(env, &field_layout);
 
                         // cast the i64 pointer to a pointer to block of memory
                         let field_cast = env
@@ -346,11 +338,9 @@ fn build_hash_tag<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let arena = env.arena;
-
             let seed_type = env.context.i64_type();
 
-            let arg_type = basic_type_from_layout(arena, env.context, &layout, env.ptr_bytes);
+            let arg_type = basic_type_from_layout(env, &layout);
 
             let function_value = crate::llvm::refcounting::build_header_help(
                 env,
@@ -435,8 +425,7 @@ fn hash_tag<'a, 'ctx, 'env>(
                 // TODO drop tag id?
                 let struct_layout = Layout::Struct(field_layouts);
 
-                let wrapper_type =
-                    basic_type_from_layout(env.arena, env.context, &struct_layout, env.ptr_bytes);
+                let wrapper_type = basic_type_from_layout(env, &struct_layout);
                 debug_assert!(wrapper_type.is_struct_type());
 
                 let as_struct =
@@ -622,11 +611,9 @@ fn build_hash_list<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let arena = env.arena;
-
             let seed_type = env.context.i64_type();
 
-            let arg_type = basic_type_from_layout(arena, env.context, &layout, env.ptr_bytes);
+            let arg_type = basic_type_from_layout(env, &layout);
 
             let function_value = crate::llvm::refcounting::build_header_help(
                 env,
@@ -710,8 +697,7 @@ fn hash_list<'a, 'ctx, 'env>(
     let done_block = env.context.append_basic_block(parent, "done");
     let loop_block = env.context.append_basic_block(parent, "loop");
 
-    let element_type =
-        basic_type_from_layout(env.arena, env.context, element_layout, env.ptr_bytes);
+    let element_type = basic_type_from_layout(env, element_layout);
     let ptr_type = element_type.ptr_type(inkwell::AddressSpace::Generic);
 
     let (length, ptr) = load_list(env.builder, value, ptr_type);
@@ -788,8 +774,7 @@ fn hash_ptr_to_struct<'a, 'ctx, 'env>(
 
     let struct_layout = Layout::Struct(field_layouts);
 
-    let wrapper_type =
-        basic_type_from_layout(env.arena, env.context, &struct_layout, env.ptr_bytes);
+    let wrapper_type = basic_type_from_layout(env, &struct_layout);
     debug_assert!(wrapper_type.is_struct_type());
 
     // cast the opaque pointer to a pointer of the correct shape
@@ -822,7 +807,7 @@ fn store_and_use_as_u8_ptr<'a, 'ctx, 'env>(
     value: BasicValueEnum<'ctx>,
     layout: &Layout<'a>,
 ) -> PointerValue<'ctx> {
-    let basic_type = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+    let basic_type = basic_type_from_layout(env, &layout);
     let alloc = env.builder.build_alloca(basic_type, "store");
     env.builder.build_store(alloc, value);
 
diff --git a/compiler/gen/src/llvm/build_list.rs b/compiler/gen/src/llvm/build_list.rs
index 257a031d55..8d05ae309c 100644
--- a/compiler/gen/src/llvm/build_list.rs
+++ b/compiler/gen/src/llvm/build_list.rs
@@ -106,7 +106,7 @@ pub fn list_prepend<'a, 'ctx, 'env>(
 
     // Load the usize length from the wrapper.
     let len = list_len(builder, original_wrapper);
-    let elem_type = basic_type_from_layout(env.arena, ctx, elem_layout, env.ptr_bytes);
+    let elem_type = basic_type_from_layout(env, elem_layout);
     let ptr_type = get_ptr_type(&elem_type, AddressSpace::Generic);
     let list_ptr = load_list_ptr(builder, original_wrapper, ptr_type);
 
@@ -185,11 +185,10 @@ pub fn list_join<'a, 'ctx, 'env>(
             let builder = env.builder;
             let ctx = env.context;
 
-            let elem_type = basic_type_from_layout(env.arena, ctx, elem_layout, env.ptr_bytes);
+            let elem_type = basic_type_from_layout(env, elem_layout);
             let elem_ptr_type = get_ptr_type(&elem_type, AddressSpace::Generic);
 
-            let inner_list_type =
-                basic_type_from_layout(env.arena, ctx, &inner_list_layout, env.ptr_bytes);
+            let inner_list_type = basic_type_from_layout(env, &inner_list_layout);
 
             let outer_list_wrapper = outer_list.into_struct_value();
             let outer_list_len = list_len(builder, outer_list_wrapper);
@@ -395,8 +394,7 @@ pub fn list_get_unsafe<'a, 'ctx, 'env>(
 
     match list_layout {
         Layout::Builtin(Builtin::List(_, elem_layout)) => {
-            let ctx = env.context;
-            let elem_type = basic_type_from_layout(env.arena, ctx, elem_layout, env.ptr_bytes);
+            let elem_type = basic_type_from_layout(env, elem_layout);
             let ptr_type = get_ptr_type(&elem_type, AddressSpace::Generic);
             // Load the pointer to the array data
             let array_data_ptr = load_list_ptr(builder, wrapper_struct, ptr_type);
@@ -497,7 +495,7 @@ pub fn list_set<'a, 'ctx, 'env>(
     let build_then = || {
         let (elem, elem_layout) = args[2];
         let ctx = env.context;
-        let elem_type = basic_type_from_layout(env.arena, ctx, elem_layout, env.ptr_bytes);
+        let elem_type = basic_type_from_layout(env, elem_layout);
         let ptr_type = get_ptr_type(&elem_type, AddressSpace::Generic);
 
         let (new_wrapper, array_data_ptr) = match input_inplace {
@@ -1385,8 +1383,7 @@ pub fn list_concat<'a, 'ctx, 'env>(
                 let second_list_length_comparison = list_is_not_empty(env, second_list_len);
 
                 let build_second_list_then = || {
-                    let elem_type =
-                        basic_type_from_layout(env.arena, ctx, elem_layout, env.ptr_bytes);
+                    let elem_type = basic_type_from_layout(env, elem_layout);
                     let ptr_type = get_ptr_type(&elem_type, AddressSpace::Generic);
 
                     let (new_wrapper, _) = clone_nonempty_list(
@@ -1413,7 +1410,7 @@ pub fn list_concat<'a, 'ctx, 'env>(
             };
 
             let if_first_list_is_not_empty = || {
-                let elem_type = basic_type_from_layout(env.arena, ctx, elem_layout, env.ptr_bytes);
+                let elem_type = basic_type_from_layout(env, elem_layout);
                 let ptr_type = get_ptr_type(&elem_type, AddressSpace::Generic);
 
                 let if_second_list_is_empty = || {
diff --git a/compiler/gen/src/llvm/compare.rs b/compiler/gen/src/llvm/compare.rs
index 02b2de1fbe..0cf32263d0 100644
--- a/compiler/gen/src/llvm/compare.rs
+++ b/compiler/gen/src/llvm/compare.rs
@@ -172,7 +172,7 @@ fn build_eq<'a, 'ctx, 'env>(
             WhenRecursive::Loop(union_layout) => {
                 let layout = Layout::Union(union_layout);
 
-                let bt = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+                let bt = basic_type_from_layout(env, &layout);
 
                 // cast the i64 pointer to a pointer to block of memory
                 let field1_cast = env
@@ -377,8 +377,7 @@ fn build_list_eq<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let arena = env.arena;
-            let arg_type = basic_type_from_layout(arena, env.context, &list_layout, env.ptr_bytes);
+            let arg_type = basic_type_from_layout(env, &list_layout);
 
             let function_value = crate::llvm::refcounting::build_header_help(
                 env,
@@ -475,8 +474,7 @@ fn build_list_eq_help<'a, 'ctx, 'env>(
         env.builder.position_at_end(then_block);
 
         let builder = env.builder;
-        let element_type =
-            basic_type_from_layout(env.arena, env.context, element_layout, env.ptr_bytes);
+        let element_type = basic_type_from_layout(env, element_layout);
         let ptr_type = get_ptr_type(&element_type, AddressSpace::Generic);
         let ptr1 = load_list_ptr(env.builder, list1, ptr_type);
         let ptr2 = load_list_ptr(env.builder, list2, ptr_type);
@@ -587,9 +585,7 @@ fn build_struct_eq<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let arena = env.arena;
-            let arg_type =
-                basic_type_from_layout(arena, env.context, &struct_layout, env.ptr_bytes);
+            let arg_type = basic_type_from_layout(env, &struct_layout);
 
             let function_value = crate::llvm::refcounting::build_header_help(
                 env,
@@ -692,12 +688,7 @@ fn build_struct_eq_help<'a, 'ctx, 'env>(
                 WhenRecursive::Loop(union_layout) => {
                     let field_layout = Layout::Union(*union_layout);
 
-                    let bt = basic_type_from_layout(
-                        env.arena,
-                        env.context,
-                        &field_layout,
-                        env.ptr_bytes,
-                    );
+                    let bt = basic_type_from_layout(env, &field_layout);
 
                     // cast the i64 pointer to a pointer to block of memory
                     let field1_cast = env
@@ -777,8 +768,7 @@ fn build_tag_eq<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let arena = env.arena;
-            let arg_type = basic_type_from_layout(arena, env.context, &tag_layout, env.ptr_bytes);
+            let arg_type = basic_type_from_layout(env, &tag_layout);
 
             let function_value = crate::llvm::refcounting::build_header_help(
                 env,
@@ -897,8 +887,7 @@ fn build_tag_eq_help<'a, 'ctx, 'env>(
                 // TODO drop tag id?
                 let struct_layout = Layout::Struct(field_layouts);
 
-                let wrapper_type =
-                    basic_type_from_layout(env.arena, env.context, &struct_layout, env.ptr_bytes);
+                let wrapper_type = basic_type_from_layout(env, &struct_layout);
                 debug_assert!(wrapper_type.is_struct_type());
 
                 let struct1 = cast_block_of_memory_to_tag(
@@ -1197,8 +1186,7 @@ fn eq_ptr_to_struct<'a, 'ctx, 'env>(
 
     let struct_layout = Layout::Struct(field_layouts);
 
-    let wrapper_type =
-        basic_type_from_layout(env.arena, env.context, &struct_layout, env.ptr_bytes);
+    let wrapper_type = basic_type_from_layout(env, &struct_layout);
     debug_assert!(wrapper_type.is_struct_type());
 
     // cast the opaque pointer to a pointer of the correct shape
diff --git a/compiler/gen/src/llvm/convert.rs b/compiler/gen/src/llvm/convert.rs
index 9cefbc3fbc..4e78b10adc 100644
--- a/compiler/gen/src/llvm/convert.rs
+++ b/compiler/gen/src/llvm/convert.rs
@@ -1,5 +1,4 @@
 use bumpalo::collections::Vec;
-use bumpalo::Bump;
 use inkwell::context::Context;
 use inkwell::types::BasicTypeEnum::{self, *};
 use inkwell::types::{ArrayType, BasicType, FunctionType, IntType, PointerType, StructType};
@@ -61,21 +60,17 @@ pub fn as_const_zero<'ctx>(bt_enum: &BasicTypeEnum<'ctx>) -> BasicValueEnum<'ctx
     }
 }
 
-fn basic_type_from_function_layout<'ctx>(
-    arena: &Bump,
-    context: &'ctx Context,
+fn basic_type_from_function_layout<'a, 'ctx, 'env>(
+    env: &crate::llvm::build::Env<'a, 'ctx, 'env>,
     args: &[Layout<'_>],
     closure_type: Option<BasicTypeEnum<'ctx>>,
     ret_layout: &Layout<'_>,
-    ptr_bytes: u32,
 ) -> BasicTypeEnum<'ctx> {
-    let ret_type = basic_type_from_layout(arena, context, &ret_layout, ptr_bytes);
-    let mut arg_basic_types = Vec::with_capacity_in(args.len(), arena);
+    let ret_type = basic_type_from_layout(env, &ret_layout);
+    let mut arg_basic_types = Vec::with_capacity_in(args.len(), env.arena);
 
     for arg_layout in args.iter() {
-        arg_basic_types.push(basic_type_from_layout(
-            arena, context, arg_layout, ptr_bytes,
-        ));
+        arg_basic_types.push(basic_type_from_layout(env, arg_layout));
     }
 
     if let Some(closure) = closure_type {
@@ -88,63 +83,47 @@ fn basic_type_from_function_layout<'ctx>(
     ptr_type.as_basic_type_enum()
 }
 
-fn basic_type_from_record<'ctx>(
-    arena: &Bump,
-    context: &'ctx Context,
+fn basic_type_from_record<'a, 'ctx, 'env>(
+    env: &crate::llvm::build::Env<'a, 'ctx, 'env>,
     fields: &[Layout<'_>],
-    ptr_bytes: u32,
 ) -> BasicTypeEnum<'ctx> {
-    let mut field_types = Vec::with_capacity_in(fields.len(), arena);
+    let mut field_types = Vec::with_capacity_in(fields.len(), env.arena);
 
     for field_layout in fields.iter() {
-        field_types.push(basic_type_from_layout(
-            arena,
-            context,
-            field_layout,
-            ptr_bytes,
-        ));
+        field_types.push(basic_type_from_layout(env, field_layout));
     }
 
-    context
+    env.context
         .struct_type(field_types.into_bump_slice(), false)
         .as_basic_type_enum()
 }
 
-pub fn basic_type_from_layout<'ctx>(
-    arena: &Bump,
-    context: &'ctx Context,
+pub fn basic_type_from_layout<'a, 'ctx, 'env>(
+    env: &crate::llvm::build::Env<'a, 'ctx, 'env>,
     layout: &Layout<'_>,
-    ptr_bytes: u32,
 ) -> BasicTypeEnum<'ctx> {
     use Layout::*;
 
     match layout {
         FunctionPointer(args, ret_layout) => {
-            basic_type_from_function_layout(arena, context, args, None, ret_layout, ptr_bytes)
+            basic_type_from_function_layout(env, args, None, ret_layout)
         }
         Closure(args, closure_layout, ret_layout) => {
             let closure_data_layout = closure_layout.as_block_of_memory_layout();
-            let closure_data =
-                basic_type_from_layout(arena, context, &closure_data_layout, ptr_bytes);
+            let closure_data = basic_type_from_layout(env, &closure_data_layout);
 
-            let function_pointer = basic_type_from_function_layout(
-                arena,
-                context,
-                args,
-                Some(closure_data),
-                ret_layout,
-                ptr_bytes,
-            );
+            let function_pointer =
+                basic_type_from_function_layout(env, args, Some(closure_data), ret_layout);
 
-            context
+            env.context
                 .struct_type(&[function_pointer, closure_data], false)
                 .as_basic_type_enum()
         }
-        Pointer(layout) => basic_type_from_layout(arena, context, &layout, ptr_bytes)
+        Pointer(layout) => basic_type_from_layout(env, &layout)
             .ptr_type(AddressSpace::Generic)
             .into(),
-        PhantomEmptyStruct => context.struct_type(&[], false).into(),
-        Struct(sorted_fields) => basic_type_from_record(arena, context, sorted_fields, ptr_bytes),
+        PhantomEmptyStruct => env.context.struct_type(&[], false).into(),
+        Struct(sorted_fields) => basic_type_from_record(env, sorted_fields),
         Union(variant) => {
             use UnionLayout::*;
             match variant {
@@ -152,40 +131,44 @@ pub fn basic_type_from_layout<'ctx>(
                 | NullableWrapped {
                     other_tags: tags, ..
                 } => {
-                    let block = block_of_memory_slices(context, tags, ptr_bytes);
+                    let block = block_of_memory_slices(env.context, tags, env.ptr_bytes);
                     block.ptr_type(AddressSpace::Generic).into()
                 }
                 NullableUnwrapped { other_fields, .. } => {
-                    let block = block_of_memory_slices(context, &[&other_fields[1..]], ptr_bytes);
+                    let block =
+                        block_of_memory_slices(env.context, &[&other_fields[1..]], env.ptr_bytes);
                     block.ptr_type(AddressSpace::Generic).into()
                 }
                 NonNullableUnwrapped(fields) => {
-                    let block = block_of_memory_slices(context, &[fields], ptr_bytes);
+                    let block = block_of_memory_slices(env.context, &[fields], env.ptr_bytes);
                     block.ptr_type(AddressSpace::Generic).into()
                 }
-                NonRecursive(_) => block_of_memory(context, layout, ptr_bytes),
+                NonRecursive(_) => block_of_memory(env.context, layout, env.ptr_bytes),
             }
         }
         RecursivePointer => {
             // TODO make this dynamic
-            context
+            env.context
                 .i64_type()
                 .ptr_type(AddressSpace::Generic)
                 .as_basic_type_enum()
         }
 
-        Builtin(builtin) => basic_type_from_builtin(arena, context, builtin, ptr_bytes),
+        Builtin(builtin) => basic_type_from_builtin(env, builtin),
     }
 }
 
-pub fn basic_type_from_builtin<'ctx>(
-    _arena: &Bump,
-    context: &'ctx Context,
+pub fn basic_type_from_builtin<'a, 'ctx, 'env>(
+    env: &crate::llvm::build::Env<'a, 'ctx, 'env>,
     builtin: &Builtin<'_>,
-    ptr_bytes: u32,
 ) -> BasicTypeEnum<'ctx> {
     use Builtin::*;
 
+    let zig_dict_type = env.module.get_struct_type("dict.RocDict").unwrap();
+
+    let context = env.context;
+    let ptr_bytes = env.ptr_bytes;
+
     match builtin {
         Int128 => context.i128_type().as_basic_type_enum(),
         Int64 => context.i64_type().as_basic_type_enum(),
@@ -198,8 +181,8 @@ pub fn basic_type_from_builtin<'ctx>(
         Float64 => context.f64_type().as_basic_type_enum(),
         Float32 => context.f32_type().as_basic_type_enum(),
         Float16 => context.f16_type().as_basic_type_enum(),
-        Dict(_, _) | EmptyDict => dict(context, ptr_bytes).into(),
-        Set(_) | EmptySet => panic!("TODO layout_to_basic_type for Builtin::Set"),
+        Dict(_, _) | EmptyDict => zig_dict_type.into(),
+        Set(_) | EmptySet => zig_dict_type.into(),
         List(_, _) | Str | EmptyStr => collection(context, ptr_bytes).into(),
         EmptyList => BasicTypeEnum::StructType(collection(context, ptr_bytes)),
     }
@@ -273,20 +256,6 @@ pub fn collection(ctx: &Context, ptr_bytes: u32) -> StructType<'_> {
     ctx.struct_type(&[u8_ptr.into(), usize_type.into()], false)
 }
 
-pub fn dict(ctx: &Context, ptr_bytes: u32) -> StructType<'_> {
-    let usize_type = ptr_int(ctx, ptr_bytes);
-    let u8_ptr = ctx.i8_type().ptr_type(AddressSpace::Generic);
-
-    ctx.struct_type(
-        &[u8_ptr.into(), usize_type.into(), usize_type.into()],
-        false,
-    )
-}
-
-pub fn dict_ptr(ctx: &Context, ptr_bytes: u32) -> PointerType<'_> {
-    dict(ctx, ptr_bytes).ptr_type(AddressSpace::Generic)
-}
-
 pub fn ptr_int(ctx: &Context, ptr_bytes: u32) -> IntType<'_> {
     match ptr_bytes {
         1 => ctx.i8_type(),
diff --git a/compiler/gen/src/llvm/refcounting.rs b/compiler/gen/src/llvm/refcounting.rs
index 1459564f32..ad6c1d24de 100644
--- a/compiler/gen/src/llvm/refcounting.rs
+++ b/compiler/gen/src/llvm/refcounting.rs
@@ -586,7 +586,7 @@ fn modify_refcount_layout_help<'a, 'ctx, 'env>(
             WhenRecursive::Loop(union_layout) => {
                 let layout = Layout::Union(*union_layout);
 
-                let bt = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+                let bt = basic_type_from_layout(env, &layout);
 
                 // cast the i64 pointer to a pointer to block of memory
                 let field_cast = env
@@ -634,7 +634,7 @@ fn modify_refcount_list<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let basic_type = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+            let basic_type = basic_type_from_layout(env, &layout);
             let function_value = build_header(env, basic_type, mode, &fn_name);
 
             modify_refcount_list_help(
@@ -711,9 +711,7 @@ fn modify_refcount_list_help<'a, 'ctx, 'env>(
     builder.position_at_end(modification_block);
 
     if element_layout.contains_refcounted() {
-        let ptr_type =
-            basic_type_from_layout(env.arena, env.context, element_layout, env.ptr_bytes)
-                .ptr_type(AddressSpace::Generic);
+        let ptr_type = basic_type_from_layout(env, element_layout).ptr_type(AddressSpace::Generic);
 
         let (len, ptr) = load_list(env.builder, original_wrapper, ptr_type);
 
@@ -774,7 +772,7 @@ fn modify_refcount_str<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let basic_type = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+            let basic_type = basic_type_from_layout(env, &layout);
             let function_value = build_header(env, basic_type, mode, &fn_name);
 
             modify_refcount_str_help(env, mode, layout, function_value);
@@ -874,7 +872,7 @@ fn modify_refcount_dict<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let basic_type = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+            let basic_type = basic_type_from_layout(env, &layout);
             let function_value = build_header(env, basic_type, mode, &fn_name);
 
             modify_refcount_dict_help(
@@ -1192,12 +1190,7 @@ fn build_rec_union_help<'a, 'ctx, 'env>(
 
         env.builder.position_at_end(block);
 
-        let wrapper_type = basic_type_from_layout(
-            env.arena,
-            env.context,
-            &Layout::Struct(field_layouts),
-            env.ptr_bytes,
-        );
+        let wrapper_type = basic_type_from_layout(env, &Layout::Struct(field_layouts));
 
         // cast the opaque pointer to a pointer of the correct shape
         let struct_ptr = env
@@ -1498,12 +1491,7 @@ fn modify_refcount_union_help<'a, 'ctx, 'env>(
         let block = env.context.append_basic_block(parent, "tag_id_modify");
         env.builder.position_at_end(block);
 
-        let wrapper_type = basic_type_from_layout(
-            env.arena,
-            env.context,
-            &Layout::Struct(field_layouts),
-            env.ptr_bytes,
-        );
+        let wrapper_type = basic_type_from_layout(env, &Layout::Struct(field_layouts));
 
         debug_assert!(wrapper_type.is_struct_type());
         let wrapper_struct = cast_block_of_memory_to_tag(env.builder, wrapper_struct, wrapper_type);