Use error handler to report errors

include/fmt/format.h

@@ -2018,18 +2018,18 @@ class context_base : public parse_context<Char>{
   basic_args<Context> args() const { return args_; }
 
   // Returns the argument with specified index.
-  format_arg do_get_arg(unsigned arg_index, const char *&error) {
+  format_arg do_get_arg(unsigned arg_index) {
     format_arg arg = args_[arg_index];
-    if (!arg && !error)
-      error = "argument index out of range";
+    if (!arg)
+      this->on_error("argument index out of range");
     return arg;
   }
 
   // Checks if manual indexing is used and returns the argument with
   // specified index.
-  format_arg get_arg(unsigned arg_index, const char *&error) {
+  format_arg get_arg(unsigned arg_index) {
     return this->check_no_auto_index() ?
-      this->do_get_arg(arg_index, error) : format_arg();
+      this->do_get_arg(arg_index) : format_arg();
   }
 
  public:
@@ -2751,19 +2751,11 @@ class basic_context :
     : Base(format_str, args) {}
 
   format_arg next_arg() {
-    const char *error = 0;
-    format_arg arg = this->do_get_arg(this->next_arg_index(), error);
-    if (error)
-      FMT_THROW(format_error(error));
-    return arg;
+    return this->do_get_arg(this->next_arg_index());
   }
 
   format_arg get_arg(unsigned arg_index) {
-    const char *error = 0;
-    format_arg arg = this->do_get_arg(arg_index, error);
-    if (error)
-      FMT_THROW(format_error(error));
-    return arg;
+    return this->do_get_arg(arg_index);
   }
 
   // Checks if manual indexing is used and returns the argument with

include/fmt/printf.h

@@ -367,18 +367,9 @@ template <typename Char, typename AF>
 typename printf_context<Char, AF>::format_arg printf_context<Char, AF>::get_arg(
     iterator it, unsigned arg_index) {
   (void)it;
-  const char *error = 0;
-  format_arg arg;
-  if (arg_index == std::numeric_limits<unsigned>::max()) {
-    arg_index = this->next_arg_index();
-    if (!error)
-      arg = this->do_get_arg(arg_index, error);
-  } else {
-    arg = Base::get_arg(arg_index - 1, error);
-  }
-  if (error)
-    FMT_THROW(format_error(!*it ? "invalid format string" : error));
-  return arg;
+  if (arg_index == std::numeric_limits<unsigned>::max())
+    return this->do_get_arg(this->next_arg_index());
+  return Base::get_arg(arg_index - 1);
 }
 
 template <typename Char, typename AF>

test/format-test.cc

@@ -1906,4 +1906,7 @@ TEST(FormatTest, FormatStringErrors) {
   EXPECT_ERROR("{1}{}",
                "cannot switch from manual to automatic argument indexing",
                int, int);
+  EXPECT_ERROR("{}{1}",
+               "cannot switch from automatic to manual argument indexing",
+               int, int);
 }

test/printf-test.cc

@@ -116,7 +116,7 @@ TEST(PrintfTest, InvalidArgIndex) {
       format_error, "argument index out of range");
 
   EXPECT_THROW_MSG(fmt::sprintf("%2$", 42),
-      format_error, "invalid format string");
+      format_error, "argument index out of range");
   EXPECT_THROW_MSG(fmt::sprintf(format("%{}$d", BIG_NUM), 42),
       format_error, "number is too big");
 }