From 47c33d19a9a6112cd28b52d0350ad5830d4476ea Mon Sep 17 00:00:00 2001
From: Yingchi Long <i@lyc.dev>
Date: Wed, 24 Jan 2024 00:00:28 +0800
Subject: [PATCH] libnixf: parse variable

---
 libnixf/include/nixf/Parse/Nodes.h | 10 ++++++++++
 libnixf/src/Parse/Parser.cpp       |  7 +++++++
 libnixf/test/Parse/Parser.cpp      | 14 ++++++++++++++
 3 files changed, 31 insertions(+)

diff --git a/libnixf/include/nixf/Parse/Nodes.h b/libnixf/include/nixf/Parse/Nodes.h
index f9eab5814..f060a048e 100644
--- a/libnixf/include/nixf/Parse/Nodes.h
+++ b/libnixf/include/nixf/Parse/Nodes.h
@@ -35,6 +35,7 @@ class Node {
     NK_BeginExpr,
     NK_ExprInt,
     NK_ExprFloat,
+    NK_ExprVar,
     NK_ExprString,
     NK_ExprPath,
     NK_ExprParen,
@@ -188,6 +189,15 @@ class Identifier : public Node {
   [[nodiscard]] const std::string &name() const { return Name; }
 };
 
+class ExprVar : public Expr {
+  std::shared_ptr<Identifier> ID;
+
+public:
+  ExprVar(RangeTy Range, std::shared_ptr<Identifier> ID)
+      : Expr(NK_ExprVar, Range), ID(std::move(ID)) {}
+  [[nodiscard]] const std::shared_ptr<Identifier> &id() const { return ID; }
+};
+
 class AttrName : public Node {
 public:
   enum AttrNameKind { ANK_ID, ANK_String, ANK_Interpolation };
diff --git a/libnixf/src/Parse/Parser.cpp b/libnixf/src/Parse/Parser.cpp
index b767b404b..acb25d1cb 100644
--- a/libnixf/src/Parse/Parser.cpp
+++ b/libnixf/src/Parse/Parser.cpp
@@ -468,6 +468,7 @@ class Parser {
   }
 
   /// expr_simple :  INT
+  ///             | ID
   ///             | FLOAT
   ///             | string
   ///             | indented_string
@@ -481,6 +482,12 @@ class Parser {
   std::shared_ptr<Expr> parseExprSimple() {
     Token Tok = peek();
     switch (Tok.kind()) {
+    case tok_id: {
+      consume();
+      auto ID =
+          std::make_shared<Identifier>(Tok.range(), std::string(Tok.view()));
+      return std::make_shared<ExprVar>(Tok.range(), std::move(ID));
+    }
     case tok_int: {
       consume();
       NixInt N;
diff --git a/libnixf/test/Parse/Parser.cpp b/libnixf/test/Parse/Parser.cpp
index d0dbf7882..4a714a148 100644
--- a/libnixf/test/Parse/Parser.cpp
+++ b/libnixf/test/Parse/Parser.cpp
@@ -546,4 +546,18 @@ TEST(Parser, AttrsExtraDot) {
   ASSERT_EQ(F2.newText(), "\"dummy\"");
 }
 
+TEST(Parser, ExprVar) {
+  auto Src = R"(a)"sv;
+
+  std::vector<Diagnostic> Diags;
+  auto AST = nixf::parse(Src, Diags);
+
+  ASSERT_TRUE(AST);
+  ASSERT_EQ(AST->kind(), Node::NK_ExprVar);
+  ASSERT_TRUE(AST->range().begin().isAt(0, 0, 0));
+  ASSERT_TRUE(AST->range().end().isAt(0, 1, 1));
+
+  ASSERT_EQ(Diags.size(), 0);
+}
+
 } // namespace