feat: support callback signatures and many-pointer addition

source/lower/lower.hon

@@ -1065,7 +1065,7 @@ lower_expression proc(state @mut State, id ast.NodeId) ir.ValueId ! (mem.AllocEr
             # ranges have no physical value; only lower_for decomposes an iterable.
             if (!trap_type(state, id)) unreachable
         }
-        .array_type, .pointer_type, .record_type, .enum_type, .union_type, .distinct_type: {
+        .array_type, .pointer_type, .function_type, .record_type, .enum_type, .union_type, .distinct_type: {
             if (!trap_type(state, id)) {
                 trap(state, try diagnostics.add(state.diagnostics, .type_not_value, span), span)
             }
@@ -1240,6 +1240,14 @@ lower_expression proc(state @mut State, id ast.NodeId) ir.ValueId ! (mem.AllocEr
             if (state.terminated) return ir.no_value
             right :: try lower_expression(state, expression.right)
             if (state.terminated or trap_type(state, id)) return ir.no_value
+            if (expression.operator == .add and type == .pointer) {
+                pointer :: typecheck.pointer_type(state.checked, typecheck.type_of(state.checked, id).pointer_type)
+                return try emit(state, ir.Instruction{
+                    op = .pointer_offset, type = .pointer, left = left, right = right,
+                    pointee = lower_type(state, pointer.element),
+                    array_type = try array_shape(state, pointer.element), span = span,
+                })
+            }
             op ir.Op :: match expression.operator {
                 .add: .add
                 .subtract: .subtract