From 3c30440d65b9522aed317e535aa59a80f12bde56 Mon Sep 17 00:00:00 2001
From: Konstantin Nazarov <mail@knazarov.com>
Date: Tue, 10 Sep 2024 01:42:47 +0100
Subject: [PATCH] Add location-aware error reporting function to the compiler

---
 src/compiler.cpp | 24 +++++++++++++++++++++---
 src/compiler.hpp | 12 ++++++++++--
 src/valeri.cpp   | 13 ++++++++-----
 3 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/src/compiler.cpp b/src/compiler.cpp
index fe3b367..076cbea 100644
--- a/src/compiler.cpp
+++ b/src/compiler.cpp
@@ -170,7 +170,7 @@ Result<bool> is_comparison_op(Symbol& sym) {
   return false;
 }
 
-Result<Value> Compiler::compile(Value& expr) {
+Result<Value> Compiler::compile(const Value& expr) {
   auto context = TRY(Context::create());
 
   // If expression is empty - just return nil
@@ -1020,7 +1020,25 @@ Result<Expression> Compiler::compile_symbol(Context& context,
   return std::move(ex);
 }
 
-Result<Value> compile(Value& expr) {
-  Compiler c = Compiler();
+Result<Expression> Compiler::syntax_error(const Value& expr, const char* msg) {
+  if (expr.is<Syntax>()) {
+    Syntax& stx = *expr.to<Syntax>();
+    auto srcloc = TRY(stx.srcloc());
+    SrcLoc& loc = *srcloc.to<SrcLoc>();
+    auto range = loc.sourcerange();
+    auto pos = range.start;
+
+    return ERROR_FMT(SyntaxError, _fname, ":", pos.line, ":", pos.column,
+                     " Syntax error: ", msg);
+  }
+  return ERROR_FMT(SyntaxError, _fname, " Syntax error: ", msg);
+}
+
+Result<Compiler> Compiler::create(const String& fname) {
+  return Compiler(TRY(fname.copy()));
+}
+
+Result<Value> compile(const String& fname, const Value& expr) {
+  Compiler c = TRY(Compiler::create(fname));
   return c.compile(expr);
 }
diff --git a/src/compiler.hpp b/src/compiler.hpp
index 87af4ac..2c8ff74 100644
--- a/src/compiler.hpp
+++ b/src/compiler.hpp
@@ -27,8 +27,11 @@ struct Expression {
 class Compiler {
  public:
   Compiler() {}
+  Compiler(String&& fname) : _fname(std::move(fname)) {}
 
-  Result<Value> compile(Value& expr);
+  static Result<Compiler> create(const String& fname);
+
+  Result<Value> compile(const Value& expr);
   Result<Expression> compile_expr(Context& context, const Value& expr);
   Result<Expression> compile_list(Context& context, const Value& expr);
   Result<Expression> compile_primop(Context& context, Symbol& op,
@@ -57,6 +60,11 @@ class Compiler {
                                  const Value& expr);
   Result<Expression> compile_body(Context& context, const Value& expr);
   Result<Expression> compile_function_call(Context& context, const Value& expr);
+
+  Result<Expression> syntax_error(const Value& expr, const char* message);
+
+ private:
+  String _fname;
 };
 
-Result<Value> compile(Value& expr);
+Result<Value> compile(const String& fname, const Value& expr);
diff --git a/src/valeri.cpp b/src/valeri.cpp
index 20c7ce6..1124612 100644
--- a/src/valeri.cpp
+++ b/src/valeri.cpp
@@ -13,12 +13,12 @@
 
 StaticArena<64 * 1024 * 1024> arena;
 
-Result<Value> run_string(const String& src) {
+Result<Value> run_string(const String& fname, const String& src) {
   auto parsed = TRY(read_multiple(src));
 
   TRY(arena_gc());
 
-  auto compiled = TRY(compile(parsed));
+  auto compiled = TRY(compile(fname, parsed));
   Module& mod = *compiled.to<Module>();
 
   auto vm = TRY(VM::create());
@@ -44,6 +44,7 @@ Result<void> print_error(const Result<Value>& res) {
 Result<void> run_repl() {
   Dict globals = TRY(Dict::create());
 
+  auto fname = TRY(String::create("<stdin>"));
   while (true) {
     auto src = TRY(read_line("valeri> "));
     auto maybe_parsed = read_multiple(src);
@@ -53,7 +54,7 @@ Result<void> run_repl() {
     }
 
     auto parsed = maybe_parsed.release_value();
-    auto compiled = TRY(compile(parsed));
+    auto compiled = TRY(compile(fname, parsed));
     Module& mod = *compiled.to<Module>();
     auto vm = TRY(VM::create());
     auto maybe_res = vm.run(mod, globals);
@@ -83,10 +84,12 @@ Result<void> run(int argc, const char* argv[]) {
       return run_repl();
     }
     src = TRY(read_stdin());
-    TRY(run_string(src));
+    auto fname = TRY(String::create("<stdin>"));
+    TRY(run_string(fname, src));
   } else {
     src = TRY(read_file(argv[1]));
-    TRY(run_string(src));
+    auto fname = TRY(String::create(argv[1]));
+    TRY(run_string(fname, src));
   }
 
   return Result<void>();