cleanup librustc_errors Handler code.

src/librustc_errors/lib.rs

@@ -302,6 +302,9 @@ pub struct Handler {
     inner: Lock<HandlerInner>,
 }
 
+/// This inner struct exists to keep it all behind a single lock;
+/// this is done to prevent possible deadlocks in a multi-threaded compiler,
+/// as well as inconsistent state observation.
 struct HandlerInner {
     flags: HandlerFlags,
     /// The number of errors that have been emitted, including duplicates.
@@ -382,52 +385,65 @@ impl Drop for HandlerInner {
 }
 
 impl Handler {
-    pub fn with_tty_emitter(color_config: ColorConfig,
-                            can_emit_warnings: bool,
-                            treat_err_as_bug: Option<usize>,
-                            cm: Option<Lrc<SourceMapperDyn>>)
-                            -> Handler {
-        Handler::with_tty_emitter_and_flags(
+    pub fn with_tty_emitter(
+        color_config: ColorConfig,
+        can_emit_warnings: bool,
+        treat_err_as_bug: Option<usize>,
+        cm: Option<Lrc<SourceMapperDyn>>,
+    ) -> Self {
+        Self::with_tty_emitter_and_flags(
             color_config,
             cm,
             HandlerFlags {
                 can_emit_warnings,
                 treat_err_as_bug,
                 .. Default::default()
-            })
+            },
+        )
     }
 
-    pub fn with_tty_emitter_and_flags(color_config: ColorConfig,
-                                      cm: Option<Lrc<SourceMapperDyn>>,
-                                      flags: HandlerFlags)
-                                      -> Handler {
+    pub fn with_tty_emitter_and_flags(
+        color_config: ColorConfig,
+        cm: Option<Lrc<SourceMapperDyn>>,
+        flags: HandlerFlags,
+    ) -> Self {
         let emitter = Box::new(EmitterWriter::stderr(
-            color_config, cm, false, false, None, flags.external_macro_backtrace));
-        Handler::with_emitter_and_flags(emitter, flags)
+            color_config,
+            cm,
+            false,
+            false,
+            None,
+            flags.external_macro_backtrace,
+        ));
+        Self::with_emitter_and_flags(emitter, flags)
     }
 
-    pub fn with_emitter(can_emit_warnings: bool,
-                        treat_err_as_bug: Option<usize>,
-                        e: Box<dyn Emitter + sync::Send>)
-                        -> Handler {
+    pub fn with_emitter(
+        can_emit_warnings: bool,
+        treat_err_as_bug: Option<usize>,
+        emitter: Box<dyn Emitter + sync::Send>,
+    ) -> Self {
         Handler::with_emitter_and_flags(
-            e,
+            emitter,
             HandlerFlags {
                 can_emit_warnings,
                 treat_err_as_bug,
                 .. Default::default()
-            })
+            },
+        )
     }
 
-    pub fn with_emitter_and_flags(e: Box<dyn Emitter + sync::Send>, flags: HandlerFlags) -> Handler
-    {
-        Handler {
+    pub fn with_emitter_and_flags(
+        emitter: Box<dyn Emitter + sync::Send>,
+        flags: HandlerFlags
+    ) -> Self {
+        Self {
             flags,
             inner: Lock::new(HandlerInner {
                 flags,
                 err_count: 0,
                 deduplicated_err_count: 0,
-                emitter: e,
+                emitter,
                 continue_after_error: true,
                 delayed_span_bugs: Vec::new(),
                 taught_diagnostics: Default::default(),
@@ -474,7 +490,8 @@ impl Handler {
                 "{}:{}: already existing stashed diagnostic with (span = {:?}, key = {:?})",
                 file!(), line!(), span, key
             ));
-            inner.emit_explicit_bug(&old_diag);
+            inner.emit_diag_at_span(old_diag, span);
+            panic!(ExplicitBug);
         }
     }
 
@@ -492,34 +509,35 @@ impl Handler {
         self.inner.borrow_mut().emit_stashed_diagnostics();
     }
 
+    /// Construct a dummy builder with `Level::Cancelled`.
+    ///
+    /// Using this will neither report anything to the user (e.g. a warning),
+    /// nor will compilation cancel as a result.
     pub fn struct_dummy(&self) -> DiagnosticBuilder<'_> {
         DiagnosticBuilder::new(self, Level::Cancelled, "")
     }
 
-    pub fn struct_span_warn<S: Into<MultiSpan>>(&self,
-                                                sp: S,
-                                                msg: &str)
-                                                -> DiagnosticBuilder<'_> {
-        let mut result = DiagnosticBuilder::new(self, Level::Warning, msg);
-        result.set_span(sp);
-        if !self.flags.can_emit_warnings {
-            result.cancel();
-        }
+    /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
+    pub fn struct_span_warn(&self, span: impl Into<MultiSpan>, msg: &str) -> DiagnosticBuilder<'_> {
+        let mut result = self.struct_warn(msg);
+        result.set_span(span);
         result
     }
-    pub fn struct_span_warn_with_code<S: Into<MultiSpan>>(&self,
-                                                          sp: S,
-                                                          msg: &str,
-                                                          code: DiagnosticId)
-                                                          -> DiagnosticBuilder<'_> {
-        let mut result = DiagnosticBuilder::new(self, Level::Warning, msg);
-        result.set_span(sp);
+
+    /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
+    /// Also include a code.
+    pub fn struct_span_warn_with_code(
+        &self,
+        span: impl Into<MultiSpan>,
+        msg: &str,
+        code: DiagnosticId,
+    ) -> DiagnosticBuilder<'_> {
+        let mut result = self.struct_span_warn(span, msg);
         result.code(code);
-        if !self.flags.can_emit_warnings {
-            result.cancel();
-        }
         result
     }
+
+    /// Construct a builder at the `Warning` level with the `msg`.
     pub fn struct_warn(&self, msg: &str) -> DiagnosticBuilder<'_> {
         let mut result = DiagnosticBuilder::new(self, Level::Warning, msg);
         if !self.flags.can_emit_warnings {
@@ -527,136 +545,141 @@ impl Handler {
         }
         result
     }
-    pub fn struct_span_err<S: Into<MultiSpan>>(&self,
-                                               sp: S,
-                                               msg: &str)
-                                               -> DiagnosticBuilder<'_> {
-        let mut result = DiagnosticBuilder::new(self, Level::Error, msg);
-        result.set_span(sp);
+
+    /// Construct a builder at the `Error` level at the given `span` and with the `msg`.
+    pub fn struct_span_err(&self, span: impl Into<MultiSpan>, msg: &str) -> DiagnosticBuilder<'_> {
+        let mut result = self.struct_err(msg);
+        result.set_span(span);
         result
     }
-    pub fn struct_span_err_with_code<S: Into<MultiSpan>>(&self,
-                                                         sp: S,
-                                                         msg: &str,
-                                                         code: DiagnosticId)
-                                                         -> DiagnosticBuilder<'_> {
-        let mut result = DiagnosticBuilder::new(self, Level::Error, msg);
-        result.set_span(sp);
+
+    /// Construct a builder at the `Error` level at the given `span`, with the `msg`, and `code`.
+    pub fn struct_span_err_with_code(
+        &self,
+        span: impl Into<MultiSpan>,
+        msg: &str,
+        code: DiagnosticId,
+    ) -> DiagnosticBuilder<'_> {
+        let mut result = self.struct_span_err(span, msg);
         result.code(code);
         result
     }
+
+    /// Construct a builder at the `Error` level with the `msg`.
     // FIXME: This method should be removed (every error should have an associated error code).
     pub fn struct_err(&self, msg: &str) -> DiagnosticBuilder<'_> {
         DiagnosticBuilder::new(self, Level::Error, msg)
     }
-    pub fn struct_err_with_code(
+
+    /// Construct a builder at the `Error` level with the `msg` and the `code`.
+    pub fn struct_err_with_code(&self, msg: &str, code: DiagnosticId) -> DiagnosticBuilder<'_> {
+        let mut result = self.struct_err(msg);
+        result.code(code);
+        result
+    }
+
+    /// Construct a builder at the `Fatal` level at the given `span` and with the `msg`.
+    pub fn struct_span_fatal(
         &self,
+        span: impl Into<MultiSpan>,
+        msg: &str,
+    ) -> DiagnosticBuilder<'_> {
+        let mut result = self.struct_fatal(msg);
+        result.set_span(span);
+        result
+    }
+
+    /// Construct a builder at the `Fatal` level at the given `span`, with the `msg`, and `code`.
+    pub fn struct_span_fatal_with_code(
+        &self,
+        span: impl Into<MultiSpan>,
         msg: &str,
         code: DiagnosticId,
     ) -> DiagnosticBuilder<'_> {
-        let mut result = DiagnosticBuilder::new(self, Level::Error, msg);
-        result.code(code);
-        result
-    }
-    pub fn struct_span_fatal<S: Into<MultiSpan>>(&self,
-                                                 sp: S,
-                                                 msg: &str)
-                                                 -> DiagnosticBuilder<'_> {
-        let mut result = DiagnosticBuilder::new(self, Level::Fatal, msg);
-        result.set_span(sp);
-        result
-    }
-    pub fn struct_span_fatal_with_code<S: Into<MultiSpan>>(&self,
-                                                           sp: S,
-                                                           msg: &str,
-                                                           code: DiagnosticId)
-                                                           -> DiagnosticBuilder<'_> {
-        let mut result = DiagnosticBuilder::new(self, Level::Fatal, msg);
-        result.set_span(sp);
+        let mut result = self.struct_span_fatal(span, msg);
         result.code(code);
         result
     }
+
+    /// Construct a builder at the `Error` level with the `msg`.
     pub fn struct_fatal(&self, msg: &str) -> DiagnosticBuilder<'_> {
         DiagnosticBuilder::new(self, Level::Fatal, msg)
     }
 
-    pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, msg: &str) -> FatalError {
-        self.emit_diagnostic(Diagnostic::new(Fatal, msg).set_span(sp));
-        self.abort_if_errors_and_should_abort();
+    pub fn span_fatal(&self, span: impl Into<MultiSpan>, msg: &str) -> FatalError {
+        self.emit_diag_at_span(Diagnostic::new(Fatal, msg), span);
         FatalError
     }
-    pub fn span_fatal_with_code<S: Into<MultiSpan>>(&self,
-                                                    sp: S,
-                                                    msg: &str,
-                                                    code: DiagnosticId)
-                                                    -> FatalError {
-        self.emit_diagnostic(Diagnostic::new_with_code(Fatal, Some(code), msg).set_span(sp));
-        self.abort_if_errors_and_should_abort();
+
+    pub fn span_fatal_with_code(
+        &self,
+        span: impl Into<MultiSpan>,
+        msg: &str,
+        code: DiagnosticId,
+    ) -> FatalError {
+        self.emit_diag_at_span(Diagnostic::new_with_code(Fatal, Some(code), msg), span);
         FatalError
     }
-    pub fn span_err<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
-        self.emit_diagnostic(Diagnostic::new(Error, msg).set_span(sp));
-        self.abort_if_errors_and_should_abort();
+
+    pub fn span_err(&self, span: impl Into<MultiSpan>, msg: &str) {
+        self.emit_diag_at_span(Diagnostic::new(Error, msg), span);
     }
-    pub fn mut_span_err<S: Into<MultiSpan>>(&self,
-                                            sp: S,
-                                            msg: &str)
-                                            -> DiagnosticBuilder<'_> {
-        let mut result = DiagnosticBuilder::new(self, Level::Error, msg);
-        result.set_span(sp);
-        result
+
+    pub fn span_err_with_code(&self, span: impl Into<MultiSpan>, msg: &str, code: DiagnosticId) {
+        self.emit_diag_at_span(Diagnostic::new_with_code(Error, Some(code), msg), span);
     }
-    pub fn span_err_with_code<S: Into<MultiSpan>>(&self, sp: S, msg: &str, code: DiagnosticId) {
-        self.emit_diagnostic(Diagnostic::new_with_code(Error, Some(code), msg).set_span(sp));
-        self.abort_if_errors_and_should_abort();
+
+    pub fn span_warn(&self, span: impl Into<MultiSpan>, msg: &str) {
+        self.emit_diag_at_span(Diagnostic::new(Warning, msg), span);
     }
-    pub fn span_warn<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
-        self.emit_diagnostic(Diagnostic::new(Warning, msg).set_span(sp));
-        self.abort_if_errors_and_should_abort();
+
+    pub fn span_warn_with_code(&self, span: impl Into<MultiSpan>, msg: &str, code: DiagnosticId) {
+        self.emit_diag_at_span(Diagnostic::new_with_code(Warning, Some(code), msg), span);
     }
-    pub fn span_warn_with_code<S: Into<MultiSpan>>(&self, sp: S, msg: &str, code: DiagnosticId) {
-        self.emit_diagnostic(Diagnostic::new_with_code(Warning, Some(code), msg).set_span(sp));
-        self.abort_if_errors_and_should_abort();
+
+    pub fn span_bug(&self, span: impl Into<MultiSpan>, msg: &str) -> ! {
+        self.inner.borrow_mut().span_bug(span, msg)
     }
-    pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, msg: &str) -> ! {
-        self.inner.borrow_mut().span_bug(sp, msg)
+
+    pub fn delay_span_bug(&self, span: impl Into<MultiSpan>, msg: &str) {
+        self.inner.borrow_mut().delay_span_bug(span, msg)
     }
-    pub fn delay_span_bug<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
-        self.inner.borrow_mut().delay_span_bug(sp, msg)
+
+    pub fn span_bug_no_panic(&self, span: impl Into<MultiSpan>, msg: &str) {
+        self.emit_diag_at_span(Diagnostic::new(Bug, msg), span);
     }
-    pub fn span_bug_no_panic<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
-        self.emit_diagnostic(Diagnostic::new(Bug, msg).set_span(sp));
-        self.abort_if_errors_and_should_abort();
+
+    pub fn span_note_without_error(&self, span: impl Into<MultiSpan>, msg: &str) {
+        self.emit_diag_at_span(Diagnostic::new(Note, msg), span);
     }
-    pub fn span_note_without_error<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
-        self.emit_diagnostic(Diagnostic::new(Note, msg).set_span(sp));
-        self.abort_if_errors_and_should_abort();
-    }
-    pub fn span_note_diag(&self,
-                          sp: Span,
-                          msg: &str)
-                          -> DiagnosticBuilder<'_> {
+
+    pub fn span_note_diag(&self, span: Span, msg: &str) -> DiagnosticBuilder<'_> {
         let mut db = DiagnosticBuilder::new(self, Note, msg);
-        db.set_span(sp);
+        db.set_span(span);
         db
     }
+
     pub fn failure(&self, msg: &str) {
         self.inner.borrow_mut().failure(msg);
     }
+
     pub fn fatal(&self, msg: &str) -> FatalError {
         self.inner.borrow_mut().fatal(msg)
     }
+
     pub fn err(&self, msg: &str) {
         self.inner.borrow_mut().err(msg);
     }
+
     pub fn warn(&self, msg: &str) {
         let mut db = DiagnosticBuilder::new(self, Warning, msg);
         db.emit();
     }
+
     pub fn note_without_error(&self, msg: &str) {
-        let mut db = DiagnosticBuilder::new(self, Note, msg);
-        db.emit();
+        DiagnosticBuilder::new(self, Note, msg).emit();
     }
+
     pub fn bug(&self, msg: &str) -> ! {
         self.inner.borrow_mut().bug(msg)
     }
@@ -698,6 +721,12 @@ impl Handler {
         self.inner.borrow_mut().emit_diagnostic(diagnostic)
     }
 
+    fn emit_diag_at_span(&self, mut diag: Diagnostic, sp: impl Into<MultiSpan>) {
+        let mut inner = self.inner.borrow_mut();
+        inner.emit_diagnostic(diag.set_span(sp));
+        inner.abort_if_errors_and_should_abort();
+    }
+
     pub fn emit_artifact_notification(&self, path: &Path, artifact_type: &str) {
         self.inner.borrow_mut().emit_artifact_notification(path, artifact_type)
     }
@@ -837,17 +866,17 @@ impl HandlerInner {
         }
     }
 
-    fn span_bug<S: Into<MultiSpan>>(&mut self, sp: S, msg: &str) -> ! {
-        self.emit_explicit_bug(Diagnostic::new(Bug, msg).set_span(sp));
-    }
-
-    fn emit_explicit_bug(&mut self, diag: &Diagnostic) -> ! {
-        self.emit_diagnostic(diag);
-        self.abort_if_errors_and_should_abort();
+    fn span_bug(&mut self, sp: impl Into<MultiSpan>, msg: &str) -> ! {
+        self.emit_diag_at_span(Diagnostic::new(Bug, msg), sp);
         panic!(ExplicitBug);
     }
 
-    fn delay_span_bug<S: Into<MultiSpan>>(&mut self, sp: S, msg: &str) {
+    fn emit_diag_at_span(&mut self, mut diag: Diagnostic, sp: impl Into<MultiSpan>) {
+        self.emit_diagnostic(diag.set_span(sp));
+        self.abort_if_errors_and_should_abort();
+    }
+
+    fn delay_span_bug(&mut self, sp: impl Into<MultiSpan>, msg: &str) {
         if self.treat_err_as_bug() {
             // FIXME: don't abort here if report_delayed_bugs is off
             self.span_bug(sp, msg);
@@ -862,18 +891,20 @@ impl HandlerInner {
     }
 
     fn fatal(&mut self, msg: &str) -> FatalError {
-        if self.treat_err_as_bug() {
-            self.bug(msg);
-        }
-        self.emit_diagnostic(&Diagnostic::new(Fatal, msg));
+        self.emit_error(Fatal, msg);
         FatalError
     }
 
     fn err(&mut self, msg: &str) {
+        self.emit_error(Error, msg);
+    }
+
+    /// Emit an error; level should be `Error` or `Fatal`.
+    fn emit_error(&mut self, level: Level, msg: &str,) {
         if self.treat_err_as_bug() {
             self.bug(msg);
         }
-        self.emit_diagnostic(&Diagnostic::new(Error, msg));
+        self.emit_diagnostic(&Diagnostic::new(level, msg));
     }
 
     fn bug(&mut self, msg: &str) -> ! {

src/librustc_typeck/check/wfcheck.rs

@@ -832,7 +832,7 @@ fn check_method_receiver<'fcx, 'tcx>(
 }
 
 fn e0307(fcx: &FnCtxt<'fcx, 'tcx>, span: Span, receiver_ty: Ty<'_>) {
-    fcx.tcx.sess.diagnostic().mut_span_err(
+    fcx.tcx.sess.diagnostic().struct_span_err(
         span,
         &format!("invalid `self` parameter type: {:?}", receiver_ty)
     ).note("type of `self` must be `Self` or a type that dereferences to it")

src/libsyntax/ext/base.rs

@@ -1041,10 +1041,6 @@ impl<'a> ExtCtxt<'a> {
     pub fn span_err_with_code<S: Into<MultiSpan>>(&self, sp: S, msg: &str, code: DiagnosticId) {
         self.parse_sess.span_diagnostic.span_err_with_code(sp, msg, code);
     }
-    pub fn mut_span_err<S: Into<MultiSpan>>(&self, sp: S, msg: &str)
-                        -> DiagnosticBuilder<'a> {
-        self.parse_sess.span_diagnostic.mut_span_err(sp, msg)
-    }
     pub fn span_warn<S: Into<MultiSpan>>(&self, sp: S, msg: &str) {
         self.parse_sess.span_diagnostic.span_warn(sp, msg);
     }

src/libsyntax/ext/expand.rs

@@ -384,7 +384,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                         let attr = attr::find_by_name(item.attrs(), sym::derive)
                             .expect("`derive` attribute should exist");
                         let span = attr.span;
-                        let mut err = self.cx.mut_span_err(span,
+                        let mut err = self.cx.struct_span_err(span,
                             "`derive` may only be applied to structs, enums and unions");
                         if let ast::AttrStyle::Inner = attr.style {
                             let trait_list = derives.iter()

src/libsyntax_ext/format.rs

@@ -295,7 +295,7 @@ impl<'a, 'b> Context<'a, 'b> {
             .filter(|fmt| fmt.precision_span.is_some())
             .count();
         if self.names.is_empty() && !numbered_position_args && count != self.args.len() {
-            e = self.ecx.mut_span_err(
+            e = self.ecx.struct_span_err(
                 sp,
                 &format!(
                     "{} positional argument{} in format string, but {}",
@@ -336,7 +336,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 sp = MultiSpan::from_span(self.fmtsp);
             }
 
-            e = self.ecx.mut_span_err(sp,
+            e = self.ecx.struct_span_err(sp,
                 &format!("invalid reference to positional {} ({})",
                          arg_list,
                          self.describe_num_args()));