Make errors in REPL more human-readable

src/common.cpp

@@ -898,3 +898,14 @@ Result<String> build_string(uint64_t value) {
   auto val = Value(TRY(Int64::create((int64_t)value)));
   return write_one(val);
 }
+
+Result<void> print_string(const String& s) {
+  auto ba = TRY(ByteArray::create(s));
+  auto size = TRY(ba.size());
+
+  for (uint64_t i = 0; i < size; i++) {
+    std::cout << TRY(ba[i]);
+  }
+
+  return Result<void>();
+}

src/common.hpp

@@ -1336,3 +1336,5 @@ Result<String> build_string(const T& value, Args&&... args) {
   first = TRY(first.concat(rest));
   return first;
 }
+
+Result<void> print_string(const String& s);

src/compiler.cpp

@@ -622,29 +622,25 @@ Result<Expression> Compiler::compile_fn(Context& context, Symbol& op,
   Context ctx = TRY(Context::create(context));
   ctx.maxreg = 1;  // Reserve the slot for function itself
 
-  auto first = TRY(expr.rest());
+  auto rest = TRY(expr.rest());
-
-  if (!TRY(syntax_is_list(first))) {
-    return ERROR(CompilationError);
-  }
 
   Value name = TRY(Nil::create());
 
-  auto maybe_name = TRY(first.first());
+  auto maybe_name = TRY(expr.second());
   auto maybe_name_unwrapped = TRY(syntax_unwrap(maybe_name));
 
   if (maybe_name_unwrapped.is<Symbol>()) {
     name = TRY(maybe_name_unwrapped.copy());
     ctx.fname = TRY(name.copy());
 
-    first = TRY(first.rest());
+    rest = TRY(rest.rest());
 
-    if (!TRY(syntax_is_list(first))) {
+    if (!TRY(syntax_is_list(rest))) {
       return ERROR(CompilationError);
     }
   }
 
-  auto param = TRY(first.first());
+  auto param = TRY(rest.first());
 
   uint64_t arity = 0;
   while (!TRY(syntax_is_nil(param))) {
@@ -655,7 +651,7 @@ Result<Expression> Compiler::compile_fn(Context& context, Symbol& op,
     auto param_name_unwrapped = TRY(syntax_unwrap(param_name));
 
     if (!param_name_unwrapped.is<Symbol>()) {
-      return ERROR(CompilationError);
+      return syntax_error(param_name, "Parameter name must be a symbol");
     }
 
     int64_t reg = TRY(ctx.add_var(param_name_unwrapped));
@@ -664,13 +660,13 @@ Result<Expression> Compiler::compile_fn(Context& context, Symbol& op,
     arity++;
   }
 
-  Value second = TRY(first.rest());
+  Value body = TRY(rest.rest());
 
-  if (!TRY(syntax_is_list(second))) {
+  if (!TRY(syntax_is_list(body))) {
     return ERROR(CompilationError);
   }
 
-  auto ex = TRY(compile_body(ctx, second));
+  auto ex = TRY(compile_body(ctx, body));
 
   TRY(ex.add_opcode(Oc::Mov, {0, (int64_t)0}, {0, (int64_t)ex.reg}));
   TRY(ex.add_opcode(Oc::Ret, {0, (int64_t)0}));
@@ -821,9 +817,6 @@ Result<Expression> Compiler::compile_body(Context& context, const Value& expr) {
   int64_t maxreg = context.maxreg;
 
   while (!cur.is<Nil>()) {
-    if (!TRY(syntax_is_list(cur))) {
-      return ERROR(CompilationError);
-    }
     auto expr_val = TRY(cur.first());
 
     // debug_print(expr_val);

src/stdlib.cpp

@@ -17,17 +17,6 @@ Result<Value> stdlib_unknown(const Array& params) {
   return ERROR(NotImplemented);
 }
 
-Result<void> print_string(const String& s) {
-  auto ba = TRY(ByteArray::create(s));
-  auto size = TRY(ba.size());
-
-  for (uint64_t i = 0; i < size; i++) {
-    std::cout << TRY(ba[i]);
-  }
-
-  return Result<void>();
-}
-
 Result<Value> stdlib_print(const Array& params) {
   auto size = TRY(params.size());
   for (uint64_t i = 0; i < size; i++) {

src/valeri.cpp

@@ -34,7 +34,9 @@ Result<void> print_error(const Result<Value>& res) {
     if (errobj.is<Nil>()) {
       debug_print(geterr());
     } else {
-      debug_print(errobj);
+      auto message = TRY(errobj.to<Error>()->message());
+      print_string(*message.to<String>());
+      std::cout << "\n";
     }
   }
 
@@ -54,7 +56,13 @@ Result<void> run_repl() {
     }
 
     auto parsed = maybe_parsed.release_value();
-    auto compiled = TRY(compile(fname, parsed));
+    auto maybe_compiled = compile(fname, parsed);
+    if (maybe_compiled.has_error()) {
+      print_error(maybe_compiled);
+      continue;
+    }
+    auto compiled = maybe_compiled.release_value();
+
     Module& mod = *compiled.to<Module>();
     auto vm = TRY(VM::create());
     auto maybe_res = vm.run(mod, globals);
@@ -85,11 +93,20 @@ Result<void> run(int argc, const char* argv[]) {
     }
     src = TRY(read_stdin());
     auto fname = TRY(String::create("<stdin>"));
-    TRY(run_string(fname, src));
+    auto res = run_string(fname, src);
+    if (res.has_error()) {
+      print_error(res);
+      exit(1);
+    }
+
   } else {
     src = TRY(read_file(argv[1]));
     auto fname = TRY(String::create(argv[1]));
-    TRY(run_string(fname, src));
+    auto res = run_string(fname, src);
+    if (res.has_error()) {
+      print_error(res);
+      exit(1);
+    }
   }
 
   return Result<void>();