feat: L Language v0.1 编译器完整实现

5 阶段编译流水线: 词法分析 → 语法分析(Pratt) → 语义分析(类型推断) → LLVM IR → .exe

模块:
- lexer: 手写状态机, 40 种 Token, // 和 /* */ 注释
- parser: Pratt 表达式解析(9 级优先级) + 递归下降语句/函数
- ast: 14 种节点类型 + 工厂函数
- sema: 作用域链符号表 + 类型推断 + 类型检查
- codegen: AST → LLVM-C API, print_i64/f64/bool 内建
- driver: 命令行 + 流水线串联 + 错误报告
- util: Arena bump allocator (8MB)

测试: 65 单元测试(词法41+语法15+语义9) + 5 集成测试 全部通过

语言特性: i64/f64/bool/void, let不可变变量, if/else, while, 递归函数

src/lexer/token.c

@@ -0,0 +1,49 @@
+#include "token.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+
+static const char* NAMES[] = {
+    [TOK_FN] = "fn", [TOK_LET] = "let", [TOK_IF] = "if",
+    [TOK_ELSE] = "else", [TOK_WHILE] = "while", [TOK_RETURN] = "return",
+    [TOK_I64] = "i64", [TOK_F64] = "f64", [TOK_BOOL] = "bool", [TOK_VOID] = "void",
+    [TOK_INT_LIT] = "整数", [TOK_FLOAT_LIT] = "浮点数",
+    [TOK_TRUE] = "true", [TOK_FALSE] = "false",
+    [TOK_IDENT] = "标识符",
+    [TOK_PLUS] = "+", [TOK_MINUS] = "-", [TOK_STAR] = "*",
+    [TOK_SLASH] = "/", [TOK_PERCENT] = "%",
+    [TOK_EQ_EQ] = "==", [TOK_BANG_EQ] = "!=",
+    [TOK_LT] = "<", [TOK_GT] = ">", [TOK_LT_EQ] = "<=", [TOK_GT_EQ] = ">=",
+    [TOK_AND_AND] = "&&", [TOK_PIPE_PIPE] = "||", [TOK_BANG] = "!",
+    [TOK_ARROW] = "->",
+    [TOK_LPAREN] = "(", [TOK_RPAREN] = ")",
+    [TOK_LBRACE] = "{", [TOK_RBRACE] = "}",
+    [TOK_COMMA] = ",", [TOK_COLON] = ":", [TOK_SEMICOLON] = ";",
+    [TOK_ASSIGN] = "=",
+    [TOK_EOF] = "EOF", [TOK_ERROR] = "错误",
+};
+
+const char* tok_name(TokenKind kind) {
+    return NAMES[kind];
+}
+
+bool tok_is_type(TokenKind kind) {
+    return kind == TOK_I64 || kind == TOK_F64 || kind == TOK_BOOL || kind == TOK_VOID;
+}
+
+int64_t tok_int_value(const Token* tok) {
+    if (tok->length <= 0 || tok->length >= 32) return 0;
+    char buf[32];
+    memcpy(buf, tok->start, tok->length);
+    buf[tok->length] = '\0';
+    return strtoll(buf, NULL, 10);
+}
+
+double tok_float_value(const Token* tok) {
+    if (tok->length <= 0 || tok->length >= 64) return 0.0;
+    char buf[64];
+    memcpy(buf, tok->start, tok->length);
+    buf[tok->length] = '\0';
+    return strtod(buf, NULL);
+}