fix interop and indexing oversights

compiler/ast/ast.odin

@@ -83,6 +83,7 @@ Expr_Kind :: enum u8 {
 	Orelse,
 	Struct_Literal,
 	Keyed,
+	Cast,
 	Negate,
 	Not,
 	Add,
@@ -109,6 +110,7 @@ Expr :: struct {
 	args:       []Expr_Id,
 	qualifier:  symbol.Id,
 	name:       symbol.Id,
+	type:       Type_Syntax,
 	left:       Expr_Id,
 	right:      Expr_Id,
 	body:       []Stmt_Id,