From 4adf9541b951e46304ba78579ce4a7388c318bb1 Mon Sep 17 00:00:00 2001
From: ValKmjolnir <lhk101lhk101@qq.com>
Date: Wed, 5 Jun 2024 00:01:46 +0800
Subject: [PATCH] :sparkles: add codegen for `??` operator

---
 src/nasal_codegen.cpp | 20 ++++++++++++++++++++
 src/nasal_codegen.h   |  1 +
 test/scalar.nas       |  7 +++++++
 3 files changed, 28 insertions(+)

diff --git a/src/nasal_codegen.cpp b/src/nasal_codegen.cpp
index 2a0b3cc..5d9e132 100644
--- a/src/nasal_codegen.cpp
+++ b/src/nasal_codegen.cpp
@@ -1059,6 +1059,9 @@ void codegen::binary_gen(binary_operator* node) {
             calc_gen(node->get_right());
             emit(op_btand, 0, node->get_location());
             return;
+        case binary_operator::binary_type::nullchain:
+            null_chain_gen(node);
+            return;
         default: break;
     }
     switch(node->get_operator_type()) {
@@ -1174,6 +1177,23 @@ void codegen::binary_gen(binary_operator* node) {
     }
 }
 
+void codegen::null_chain_gen(binary_operator* node) {
+    calc_gen(node->get_left());
+    emit(op_pnil, 0, node->get_location());
+    emit(op_eq, 0, node->get_location());
+
+    const auto jmp_false_point = code.size();
+    emit(op_jf, 0, node->get_location());
+
+    calc_gen(node->get_right());
+    const auto jmp_direct_point = code.size();
+    emit(op_jmp, 0, node->get_location());
+
+    code[jmp_false_point].num = code.size();
+    emit(op_pop, 0, node->get_location());
+    code[jmp_direct_point].num = code.size();
+}
+
 void codegen::trino_gen(ternary_operator* node) {
     calc_gen(node->get_condition());
     usize label_jump_false = code.size();
diff --git a/src/nasal_codegen.h b/src/nasal_codegen.h
index 8501426..abc42c9 100644
--- a/src/nasal_codegen.h
+++ b/src/nasal_codegen.h
@@ -148,6 +148,7 @@ private:
     void and_gen(binary_operator*);
     void unary_gen(unary_operator*);
     void binary_gen(binary_operator*);
+    void null_chain_gen(binary_operator*);
     void trino_gen(ternary_operator*);
     void calc_gen(expr*);
     void repl_mode_info_output_gen(expr*);
diff --git a/test/scalar.nas b/test/scalar.nas
index 3773749..ca8b959 100644
--- a/test/scalar.nas
+++ b/test/scalar.nas
@@ -267,3 +267,10 @@ for(var i = 1; i<=10; i += 1) {
         die("test failed: expect " ~ i ~ ", but get " ~ closure_tester[1]());
     }
 }
+
+func() {
+    var a = nil;
+    var b = nil;
+    var c = nil;
+    println(a??b??c??"a??b??c?? -> should print this text");
+}();