1 files changed, 70 insertions, 0 deletions
diff --git a/boot/lower.c b/boot/lower.c
new file mode 100644
index 0000000..1fd1a7e
--- /dev/null
+++ b/boot/lower.c
@@ -0,0 +1,70 @@
+/*
+ * lowering pass to create an ir from a catskill source tree.
+ *
+ * the idea is to fully de-sugar a catskill source file
+ * into an ir that can be very easily re-expressed into
+ * a low-level language, like our transpilation target, c.
+ *
+ * the lowering pass is itself split into two passes, one
+ * initial pass, which collects all top-level type & function
+ * declarations to build up a table of all available language objects,
+ * and then a second pass going over each function body.
+ * this de-couples usage of the functions and types from their ordering
+ * allowing for more free-flowing files than c would allow.
+ *
+ * additionally, we handle type dependencies by collecting every
+ * direct reference a type has to another, and topologically
+ * sort the types to create the correct ordering of them,
+ * pointing out any unbreakable cycles to the user as they come up.
+ *
+ * Copyright (c) 2026, Mel G. <mel@rnrd.eu>
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ */
+
+#pragma once
+
+#include "catboot.h"
+
+Type_Id
+lower_seed_primitive(struct Unit* unit, const ascii* name)
+{
+    Type_Id id = array_length(&unit->types.entries);
+    struct String name_str = string_from_static_c_string(name);
+    struct Type* type = type_new(id, TYPE_PRIMITIVE, name_str, span_empty());
+    array_push(&unit->types.entries, &type);
+
+    struct Type_Name_To_Id mapping = { .name = name_str, .id = id };
+    array_push(&unit->types.by_name, &mapping);
+
+    return id;
+}
+
+void
+lower_tree(struct Tree* tree, struct Source_File source, struct Unit* unit)
+{
+    // TODO: implement!
+    (void)tree;
+    (void)source;
+
+    unit->types.entries = array_new(struct Type*, 256);
+    unit->types.by_hash = array_new(struct Type_Hash_To_Id, 256);
+    unit->types.by_name = array_new(struct Type_Name_To_Id, 256);
+
+    unit->functions.entries = array_new(struct Function*, 256);
+    unit->functions.by_name = array_new(struct Function_Name_To_Id, 256);
+
+    unit->imports = array_new(struct Import, 32);
+    unit->type_emission_order = array_new(Type_Id, 256);
+    unit->had_error = false;
+    unit->diagnostics = array_new(struct Diagnostic, 64);
+
+    unit->types.primitive_int_id = lower_seed_primitive(unit, "int");
+    unit->types.primitive_uint_id = lower_seed_primitive(unit, "uint");
+    unit->types.primitive_bool_id = lower_seed_primitive(unit, "bool");
+    unit->types.primitive_string_id = lower_seed_primitive(unit, "string");
+    unit->types.primitive_float_id = lower_seed_primitive(unit, "float");
+    unit->types.primitive_byte_id = lower_seed_primitive(unit, "byte");
+    unit->types.primitive_ascii_id = lower_seed_primitive(unit, "ascii");
+    unit->types.primitive_void_id = lower_seed_primitive(unit, "void");
+}