condtional multi-unwrap and guard clauses

compiler/ast/ast.odin

@@ -136,14 +136,18 @@ Stmt :: struct {
 	pointer_capture: bool,
 	target:     Expr_Id,
 	expr:       Expr_Id,
-	// `If` statements use `expr` as the condition, `body` as the then-block, and
-	// `else_body` as the else-block. An `else if` chain is represented as an
-	// `else_body` holding a single nested `If` statement.
+	// `If` statements use `expr` as the condition, `captures` as optional
+	// unwrap binding names, `guard` as the optional post-unwrap boolean
+	// condition, `body` as the then-block, and `else_body` as the else-block.
+	// An `else if` chain is represented as an `else_body` holding a single
+	// nested `If` statement.
 	// `While` statements use `expr` as the condition, `body` as the loop body,
 	// and `update` as the optional post-iteration statement.
 	// `For` statements use `expr` as the iterable, `name` as the item capture,
 	// `index_name` as the optional index capture, and `pointer_capture` to
 	// distinguish `|@item|` from copy capture.
+	captures:   []symbol.Id,
+	guard:      Expr_Id,
 	body:       []Stmt_Id,
 	else_body:  []Stmt_Id,
 	update:     Stmt_Id,
@@ -263,6 +267,7 @@ destroy_module :: proc(module: ^Module) {
 		delete(expr.args, module.allocator)
 	}
 	for statement in module.statements {
+		delete(statement.captures, module.allocator)
 		delete(statement.body, module.allocator)
 		delete(statement.else_body, module.allocator)
 	}