diff --git a/fec/src/lower.c b/fec/src/lower.c
new file mode 100644
index 0000000..abd6942
--- /dev/null
+++ b/fec/src/lower.c
@@ -0,0 +1,227 @@
+#include "lower.h"
+#include <string.h>
+
+static int lower_grow_scopes(FeLowerPlan *plan)
+{
+    FeLowerScope *items;
+    unsigned capacity;
+    if (plan->scope_count < plan->scope_capacity) return 1;
+    capacity = plan->scope_capacity ? plan->scope_capacity * 2U : 8U;
+    items = (FeLowerScope *)fe_arena_alloc(plan->arena,
+                                            capacity * sizeof(FeLowerScope));
+    if (!items) return 0;
+    if (plan->scopes)
+        memcpy(items, plan->scopes,
+               plan->scope_count * sizeof(FeLowerScope));
+    plan->scopes = items;
+    plan->scope_capacity = capacity;
+    return 1;
+}
+
+static int lower_grow_cleanups(FeLowerPlan *plan)
+{
+    FeLowerCleanup *items;
+    unsigned capacity;
+    if (plan->cleanup_count < plan->cleanup_capacity) return 1;
+    capacity = plan->cleanup_capacity ? plan->cleanup_capacity * 2U : 16U;
+    items = (FeLowerCleanup *)fe_arena_alloc(plan->arena,
+                                              capacity * sizeof(FeLowerCleanup));
+    if (!items) return 0;
+    if (plan->cleanups)
+        memcpy(items, plan->cleanups,
+               plan->cleanup_count * sizeof(FeLowerCleanup));
+    plan->cleanups = items;
+    plan->cleanup_capacity = capacity;
+    return 1;
+}
+
+static unsigned lower_add_scope(FeLowerPlan *plan, FeNode *block,
+                                unsigned parent)
+{
+    FeLowerScope *scope;
+    unsigned index;
+    if (!lower_grow_scopes(plan)) return FE_LOWER_NO_SCOPE;
+    index = plan->scope_count++;
+    scope = &plan->scopes[index];
+    scope->block = block;
+    scope->parent = parent;
+    scope->ordinal = plan->next_ordinal++;
+    return index;
+}
+
+static int lower_add_cleanup(FeLowerPlan *plan, unsigned scope,
+                             FeLowerCleanupKind kind, FeNode *node,
+                             FeNode *decl, FeType *type)
+{
+    FeLowerCleanup *cleanup;
+    if (!lower_grow_cleanups(plan)) return 0;
+    cleanup = &plan->cleanups[plan->cleanup_count++];
+    cleanup->kind = kind;
+    cleanup->scope = scope;
+    cleanup->ordinal = plan->next_ordinal++;
+    cleanup->node = node;
+    cleanup->decl = decl;
+    cleanup->type = type;
+    return 1;
+}
+
+int fe_lower_type_needs_drop(const FeType *type)
+{
+    unsigned i;
+    unsigned j;
+    if (!type) return 0;
+    if (type->kind == FE_TYPE_OWNED) return 1;
+    if (type->kind == FE_TYPE_OPTIONAL)
+        return fe_lower_type_needs_drop(type->elem);
+    if (type->kind == FE_TYPE_ERROR_UNION)
+        return fe_lower_type_needs_drop(type->error_value);
+    if (type->kind == FE_TYPE_ARRAY)
+        return fe_lower_type_needs_drop(type->elem);
+    if (type->kind == FE_TYPE_STRUCT) {
+        if (type->has_drop) return 1;
+        for (i = 0; i < type->field_count; ++i)
+            if (fe_lower_type_needs_drop(type->fields[i].type)) return 1;
+        return 0;
+    }
+    if (type->kind == FE_TYPE_ENUM) {
+        for (i = 0; i < type->variant_count; ++i)
+            for (j = 0; j < type->variants[i].field_count; ++j)
+                if (fe_lower_type_needs_drop(type->variants[i].fields[j].type))
+                    return 1;
+    }
+    return 0;
+}
+
+static int lower_build_node(FeLowerPlan *plan, FeNode *node,
+                            unsigned scope);
+
+static int lower_build_list(FeLowerPlan *plan, FeNode *node,
+                            unsigned scope)
+{
+    while (node) {
+        if (!lower_build_node(plan, node, scope)) return 0;
+        node = node->next;
+    }
+    return 1;
+}
+
+static int lower_build_block(FeLowerPlan *plan, FeNode *block,
+                             unsigned parent)
+{
+    unsigned scope;
+    if (!block || block->kind != FE_N_BLOCK) return 1;
+    scope = lower_add_scope(plan, block, parent);
+    if (scope == FE_LOWER_NO_SCOPE) return 0;
+    return lower_build_list(plan, block->children, scope);
+}
+
+static int lower_build_node(FeLowerPlan *plan, FeNode *node,
+                            unsigned scope)
+{
+    FeNode *child;
+    FeType *type;
+    if (!node) return 1;
+    if (node->kind == FE_N_BLOCK)
+        return lower_build_block(plan, node, scope);
+    if (node->kind == FE_N_DEFER) {
+        if (!lower_add_cleanup(plan, scope, FE_LOWER_CLEANUP_DEFER,
+                               node->a, node, 0))
+            return 0;
+        return lower_build_node(plan, node->a, scope);
+    }
+    if (node->kind == FE_N_LET || node->kind == FE_N_VAR ||
+        node->kind == FE_N_CONST) {
+        type = node->sem_type;
+        if (fe_lower_type_needs_drop(type))
+            if (!lower_add_cleanup(plan, scope, FE_LOWER_CLEANUP_DROP,
+                                   node, node, type))
+                return 0;
+    }
+    if (!lower_build_node(plan, node->a, scope)) return 0;
+    if (!lower_build_node(plan, node->b, scope)) return 0;
+    if (!lower_build_node(plan, node->c, scope)) return 0;
+    for (child = node->children; child; child = child->next)
+        if (!lower_build_node(plan, child, scope)) return 0;
+    return 1;
+}
+
+void fe_lower_plan_init(FeLowerPlan *plan, FeArena *arena)
+{
+    if (!plan) return;
+    plan->arena = arena;
+    plan->fn = 0;
+    plan->scopes = 0;
+    plan->scope_count = 0;
+    plan->scope_capacity = 0;
+    plan->cleanups = 0;
+    plan->cleanup_count = 0;
+    plan->cleanup_capacity = 0;
+    plan->next_ordinal = 0;
+}
+
+int fe_lower_plan_build(FeLowerPlan *plan, FeNode *fn)
+{
+    if (!plan || !plan->arena || !fn || fn->kind != FE_N_FN) return 0;
+    plan->fn = fn;
+    plan->scopes = 0;
+    plan->scope_count = 0;
+    plan->scope_capacity = 0;
+    plan->cleanups = 0;
+    plan->cleanup_count = 0;
+    plan->cleanup_capacity = 0;
+    plan->next_ordinal = 0;
+    if (!fn->c) return 1;
+    return lower_build_block(plan, fn->c, FE_LOWER_NO_SCOPE);
+}
+
+unsigned fe_lower_scope_for_block(const FeLowerPlan *plan,
+                                  const FeNode *block)
+{
+    unsigned i;
+    if (!plan || !block) return FE_LOWER_NO_SCOPE;
+    for (i = 0; i < plan->scope_count; ++i)
+        if (plan->scopes[i].block == block) return i;
+    return FE_LOWER_NO_SCOPE;
+}
+
+unsigned fe_lower_collect_cleanups(const FeLowerPlan *plan,
+                                   const FeNode *from_block,
+                                   const FeNode *stop_block,
+                                   const FeLowerCleanup **out,
+                                   unsigned out_capacity)
+{
+    unsigned scope;
+    unsigned stop;
+    unsigned i;
+    unsigned count;
+    if (!plan || !from_block) return 0;
+    scope = fe_lower_scope_for_block(plan, from_block);
+    stop = stop_block ? fe_lower_scope_for_block(plan, stop_block) :
+                        FE_LOWER_NO_SCOPE;
+    count = 0;
+    while (scope != FE_LOWER_NO_SCOPE && scope != stop) {
+        for (i = plan->cleanup_count; i > 0; --i) {
+            if (plan->cleanups[i - 1U].scope != scope) continue;
+            if (out && count < out_capacity)
+                out[count] = &plan->cleanups[i - 1U];
+            ++count;
+        }
+        scope = plan->scopes[scope].parent;
+    }
+    return count;
+}
+
+int fe_lower_exit_runs_cleanup(FeLowerExitKind kind)
+{
+    return kind == FE_LOWER_EXIT_FALLTHROUGH ||
+           kind == FE_LOWER_EXIT_RETURN ||
+           kind == FE_LOWER_EXIT_ERROR_RETURN ||
+           kind == FE_LOWER_EXIT_BREAK ||
+           kind == FE_LOWER_EXIT_CONTINUE;
+}
+
+int fe_lower_exit_leaves_function(FeLowerExitKind kind)
+{
+    return kind == FE_LOWER_EXIT_RETURN ||
+           kind == FE_LOWER_EXIT_ERROR_RETURN;
+}