feat(furc/parser): add variable and group expressions

furc/include/furc/front/ast.hpp

@@ -79,8 +79,6 @@ public:
     virtual decl_type_e decl_type() const = 0;
 };
 
-class expr_node;
-
 struct var_decl_node final : public decl_node {
     decl_type_e decl_type() const override { return Variable; }
 
@@ -103,6 +101,8 @@ public:
     enum expr_type_e {
         Literal,
 
+        VarRead,
+        Group,
         BinaryOp,
         UnaryOp,
     };
@@ -114,6 +114,21 @@ public:
     virtual expr_type_e expr_type() const = 0;
 };
 
+struct var_read_expr_node final : public expr_node {
+    expr_type_e expr_type() const override { return VarRead; }
+
+    std::string name;
+
+    var_read_expr_node(std::string&& name)
+      : name(std::move(name)) {}
+};
+
+struct group_expr_node final : public expr_node {
+    expr_type_e expr_type() const override { return Group; }
+
+    expr_node* inner = nullptr;
+};
+
 struct binary_op_expr_node final : public expr_node {
     enum binary_op_type {
         Add = 0,

furc/include/furc/front/parser.hpp

@@ -27,7 +27,6 @@ private:
     stmt_node* parse_stmt();
     decl_node* parse_decl();
     expr_node* parse_expr();
-    lit_node*  parse_lit();
 
     ast_type       parse_type();
     comp_stmt_node parse_comp();

furc/src/front/parser.cpp

@@ -89,19 +89,6 @@ expr_node* parser::parse_expr() {
     return parse_expr_right(parse_expr_unary());
 }
 
-lit_node* parser::parse_lit() {
-    auto token = eat_token(token::Integer, token::Char);
-    switch (token.type) {
-    case token::Integer: {
-        return m_arena->allocate<int_lit_node>(int_lit_node(token.value.integer));
-    }
-    case token::Char: {
-        return m_arena->allocate<char_lit_node>(char_lit_node(token.value.character));
-    }
-    default: throw std::runtime_error("unreachable");
-    }
-}
-
 ast_type parser::parse_type() {
     auto token =
         eat_token(token::S8, token::U8, token::S16, token::U16, token::S32, token::U32, token::S64, token::U64);
@@ -131,7 +118,25 @@ comp_stmt_node parser::parse_comp() {
 }
 
 expr_node* parser::parse_expr_primary() {
-    return parse_lit();
+    auto token = eat_token(token::Identifier, token::LParen, token::Integer, token::Char);
+    switch (token.type) {
+    case token::Identifier: {
+        return m_arena->allocate<var_read_expr_node>(std::string(token.value.string));
+    }
+    case token::LParen: {
+        group_expr_node group;
+        group.inner = parse_expr();
+        eat_token(token::RParen);
+        return m_arena->allocate<group_expr_node>(std::move(group));
+    }
+    case token::Integer: {
+        return m_arena->allocate<int_lit_node>(int_lit_node(token.value.integer));
+    }
+    case token::Char: {
+        return m_arena->allocate<char_lit_node>(char_lit_node(token.value.character));
+    }
+    default: throw std::runtime_error("unreachable");
+    }
 }
 
 expr_node* parser::parse_expr_unary() {