Keep current behavior while accepting error count

src/librustc/session/config.rs

@@ -816,6 +816,8 @@ macro_rules! options {
             Some("crate=integer");
         pub const parse_unpretty: Option<&str> =
             Some("`string` or `string=string`");
+        pub const parse_treat_err_as_bug: Option<&str> =
+            Some("either no value or a number bigger than 0");
         pub const parse_lto: Option<&str> =
             Some("either a boolean (`yes`, `no`, `on`, `off`, etc), `thin`, \
                   `fat`, or omitted");
@@ -1022,6 +1024,13 @@ macro_rules! options {
             }
         }
 
+        fn parse_treat_err_as_bug(slot: &mut Option<usize>, v: Option<&str>) -> bool {
+            match v {
+                Some(s) => { *slot = s.parse().ok().filter(|&x| x != 0); slot.unwrap_or(0) != 0 }
+                None => { *slot = Some(1); true }
+            }
+        }
+
         fn parse_lto(slot: &mut LtoCli, v: Option<&str>) -> bool {
             if v.is_some() {
                 let mut bool_arg = None;
@@ -1234,7 +1243,7 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "parse only; do not compile, assemble, or link"),
     no_codegen: bool = (false, parse_bool, [TRACKED],
         "run all passes except codegen; no output"),
-    treat_err_as_bug: Option<usize> = (None, parse_opt_uint, [TRACKED],
+    treat_err_as_bug: Option<usize> = (None, parse_treat_err_as_bug, [TRACKED],
         "treat all errors that occur as bugs"),
     report_delayed_bugs: bool = (false, parse_bool, [TRACKED],
         "immediately print bugs registered with `delay_span_bug`"),
@@ -3212,7 +3221,7 @@ mod tests {
         assert!(reference.dep_tracking_hash() != opts.dep_tracking_hash());
 
         opts = reference.clone();
-        opts.debugging_opts.treat_err_as_bug = Some(0);
+        opts.debugging_opts.treat_err_as_bug = Some(1);
         assert!(reference.dep_tracking_hash() != opts.dep_tracking_hash());
 
         opts = reference.clone();

src/librustc_errors/lib.rs

@@ -517,7 +517,19 @@ impl Handler {
 
     fn panic_if_treat_err_as_bug(&self) {
         if self.treat_err_as_bug() {
-            panic!("encountered error with `-Z treat_err_as_bug");
+            let s = match (self.err_count(), self.flags.treat_err_as_bug.unwrap_or(0)) {
+                (0, _) => return,
+                (1, 1) => "aborting due to `-Z treat-err-as-bug=1`".to_string(),
+                (1, _) => return,
+                (count, as_bug) => {
+                    format!(
+                        "aborting after {} errors due to `-Z treat-err-as-bug={}`",
+                        count,
+                        as_bug,
+                    )
+                }
+            };
+            panic!(s);
         }
     }
 
@@ -645,14 +657,12 @@ impl Handler {
             1 => "aborting due to previous error".to_string(),
             _ => format!("aborting due to {} previous errors", self.err_count())
         };
+        let err_as_bug = self.flags.treat_err_as_bug.unwrap_or(0);
+        if self.err_count() >= err_as_bug {
+            return;
+        }
 
-        let _ = if self.treat_err_as_bug() {
-            self.fatal(&s)
-        } else {
-            // only emit one backtrace when using `-Z treat-err-as-bug=X`
-            DiagnosticBuilder::new(self, Fatal, &s).emit();
-            FatalError
-        };
+        let _ = self.fatal(&s);
 
         let can_show_explain = self.emitter.borrow().should_show_explain();
         let are_there_diagnostics = !self.emitted_diagnostic_codes.borrow().is_empty();

src/librustdoc/test.rs

@@ -67,7 +67,7 @@ pub fn run(mut options: Options) -> isize {
         let source_map = Lrc::new(SourceMap::new(sessopts.file_path_mapping()));
         let handler =
             errors::Handler::with_tty_emitter(ColorConfig::Auto,
-                                            true, false,
+                                            true, None,
                                             Some(source_map.clone()));
 
         let mut sess = session::build_session_(