Build erased types

crates/compiler/gen_llvm/src/llvm/erased.rs

@@ -1,4 +1,8 @@
-use inkwell::{types::StructType, AddressSpace};
+use inkwell::{
+    types::StructType,
+    values::{PointerValue, StructValue},
+    AddressSpace,
+};
 
 use super::build::Env;
 
@@ -17,3 +21,46 @@ pub fn basic_type<'a, 'ctx>(env: &Env<'a, 'ctx, '_>) -> StructType<'ctx> {
     env.context
         .struct_type(&[ptr_ty.into(), ptr_ty.into(), ptr_ty.into()], false)
 }
+
+fn bitcast_to_opaque_ptr<'ctx>(
+    env: &Env<'_, 'ctx, '_>,
+    value: PointerValue<'ctx>,
+) -> PointerValue<'ctx> {
+    env.builder
+        .build_bitcast(
+            value,
+            env.context.i8_type().ptr_type(AddressSpace::default()),
+            "to_opaque_ptr",
+        )
+        .into_pointer_value()
+}
+
+pub fn build<'a, 'ctx>(
+    env: &Env<'a, 'ctx, '_>,
+    value: Option<PointerValue<'ctx>>,
+    callee: PointerValue<'ctx>,
+) -> StructValue<'ctx> {
+    let struct_type = basic_type(env);
+
+    let struct_value = struct_type.const_zero().into();
+
+    let struct_value = match value {
+        Some(value) => {
+            let value = bitcast_to_opaque_ptr(env, value);
+            env.builder
+                .build_insert_value(struct_value, value, 0, "insert_value")
+                .unwrap()
+        }
+        None => struct_value,
+    };
+
+    let callee = bitcast_to_opaque_ptr(env, callee);
+    let struct_value = env
+        .builder
+        .build_insert_value(struct_value, callee, 1, "insert_callee")
+        .unwrap();
+
+    // TODO: insert refcounter
+
+    struct_value.into_struct_value()
+}