Rollup merge of #119872 - compiler-errors:eagerly-emit-delayed-bugs, r=oli-obk,nnethercote

Give me a way to emit all the delayed bugs as errors (add `-Zeagerly-emit-delayed-bugs`)

This is probably a *better* way to inspect all the delayed bugs in a program that what exists currently (and therefore makes it very easy to choose the right number `N` with `-Zemit-err-as-bug=N`, though I guess the naming is a bit ironic when you pair both of the flags together, but that feels like naming bikeshed more than anything).

This pacifies my only concern with https://github.com/rust-lang/rust/pull/119871#issuecomment-1888170259, because (afaict?) that PR doesn't allow you to intercept a delayed bug's stack trace anymore, which as someone who debugs the compiler a lot, is something that I can *promise* that I do.

r? `@nnethercote` or `@oli-obk`

compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs

@@ -85,7 +85,7 @@ fn source_string(file: Lrc<SourceFile>, line: &Line) -> String {
 /// Maps `Diagnostic::Level` to `snippet::AnnotationType`
 fn annotation_type_for_level(level: Level) -> AnnotationType {
     match level {
-        Level::Bug | Level::DelayedBug | Level::Fatal | Level::Error => AnnotationType::Error,
+        Level::Bug | Level::DelayedBug(_) | Level::Fatal | Level::Error => AnnotationType::Error,
         Level::ForceWarning(_) | Level::Warning => AnnotationType::Warning,
         Level::Note | Level::OnceNote => AnnotationType::Note,
         Level::Help | Level::OnceHelp => AnnotationType::Help,

compiler/rustc_errors/src/diagnostic.rs

@@ -1,7 +1,7 @@
 use crate::snippet::Style;
 use crate::{
-    CodeSuggestion, DiagnosticBuilder, DiagnosticMessage, EmissionGuarantee, Level, MultiSpan,
+    CodeSuggestion, DelayedBugKind, DiagnosticBuilder, DiagnosticMessage, EmissionGuarantee, Level,
-    SubdiagnosticMessage, Substitution, SubstitutionPart, SuggestionStyle,
+    MultiSpan, SubdiagnosticMessage, Substitution, SubstitutionPart, SuggestionStyle,
 };
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_error_messages::fluent_value_from_str_list_sep_by_and;
@@ -243,12 +243,15 @@ impl Diagnostic {
 
     pub fn is_error(&self) -> bool {
         match self.level {
-            Level::Bug | Level::DelayedBug | Level::Fatal | Level::Error | Level::FailureNote => {
+            Level::Bug
-                true
+            | Level::DelayedBug(DelayedBugKind::Normal)
-            }
+            | Level::Fatal
+            | Level::Error
+            | Level::FailureNote => true,
 
             Level::ForceWarning(_)
             | Level::Warning
+            | Level::DelayedBug(DelayedBugKind::GoodPath)
             | Level::Note
             | Level::OnceNote
             | Level::Help
@@ -318,7 +321,7 @@ impl Diagnostic {
             "downgrade_to_delayed_bug: cannot downgrade {:?} to DelayedBug: not an error",
             self.level
         );
-        self.level = Level::DelayedBug;
+        self.level = Level::DelayedBug(DelayedBugKind::Normal);
     }
 
     /// Appends a labeled span to the diagnostic.

compiler/rustc_errors/src/lib.rs

@@ -519,6 +519,12 @@ fn default_track_diagnostic(diag: Diagnostic, f: &mut dyn FnMut(Diagnostic)) {
 pub static TRACK_DIAGNOSTIC: AtomicRef<fn(Diagnostic, &mut dyn FnMut(Diagnostic))> =
     AtomicRef::new(&(default_track_diagnostic as _));
 
+#[derive(Copy, PartialEq, Eq, Clone, Hash, Debug, Encodable, Decodable)]
+pub enum DelayedBugKind {
+    Normal,
+    GoodPath,
+}
+
 #[derive(Copy, Clone, Default)]
 pub struct DiagCtxtFlags {
     /// If false, warning-level lints are suppressed.
@@ -527,6 +533,9 @@ pub struct DiagCtxtFlags {
     /// If Some, the Nth error-level diagnostic is upgraded to bug-level.
     /// (rustc: see `-Z treat-err-as-bug`)
     pub treat_err_as_bug: Option<NonZeroUsize>,
+    /// Eagerly emit delayed bugs as errors, so that the compiler debugger may
+    /// see all of the errors being emitted at once.
+    pub eagerly_emit_delayed_bugs: bool,
     /// Show macro backtraces.
     /// (rustc: see `-Z macro-backtrace`)
     pub macro_backtrace: bool,
@@ -541,8 +550,7 @@ impl Drop for DiagCtxtInner {
         self.emit_stashed_diagnostics();
 
         if !self.has_errors() {
-            let bugs = std::mem::replace(&mut self.span_delayed_bugs, Vec::new());
+            self.flush_delayed(DelayedBugKind::Normal)
-            self.flush_delayed(bugs, "no errors encountered even though `span_delayed_bug` issued");
         }
 
         // FIXME(eddyb) this explains what `good_path_delayed_bugs` are!
@@ -551,11 +559,7 @@ impl Drop for DiagCtxtInner {
         // lints can be `#[allow]`'d, potentially leading to this triggering.
         // Also, "good path" should be replaced with a better naming.
         if !self.has_printed && !self.suppressed_expected_diag && !std::thread::panicking() {
-            let bugs = std::mem::replace(&mut self.good_path_delayed_bugs, Vec::new());
+            self.flush_delayed(DelayedBugKind::GoodPath);
-            self.flush_delayed(
-                bugs,
-                "no warnings or errors encountered even though `good_path_delayed_bugs` issued",
-            );
         }
 
         if self.check_unstable_expect_diagnostics {
@@ -865,7 +869,8 @@ impl DiagCtxt {
         if treat_next_err_as_bug {
             self.bug(msg);
         }
-        DiagnosticBuilder::<ErrorGuaranteed>::new(self, DelayedBug, msg).emit()
+        DiagnosticBuilder::<ErrorGuaranteed>::new(self, DelayedBug(DelayedBugKind::Normal), msg)
+            .emit()
     }
 
     /// Like `delayed_bug`, but takes an additional span.
@@ -882,16 +887,15 @@ impl DiagCtxt {
         if treat_next_err_as_bug {
             self.span_bug(sp, msg);
         }
-        DiagnosticBuilder::<ErrorGuaranteed>::new(self, DelayedBug, msg).with_span(sp).emit()
+        DiagnosticBuilder::<ErrorGuaranteed>::new(self, DelayedBug(DelayedBugKind::Normal), msg)
+            .with_span(sp)
+            .emit()
     }
 
     // FIXME(eddyb) note the comment inside `impl Drop for DiagCtxtInner`, that's
     // where the explanation of what "good path" is (also, it should be renamed).
     pub fn good_path_delayed_bug(&self, msg: impl Into<DiagnosticMessage>) {
-        let mut inner = self.inner.borrow_mut();
+        DiagnosticBuilder::<()>::new(self, DelayedBug(DelayedBugKind::GoodPath), msg).emit()
-        let diagnostic = Diagnostic::new(DelayedBug, msg);
-        let backtrace = std::backtrace::Backtrace::capture();
-        inner.good_path_delayed_bugs.push(DelayedDiagnostic::with_backtrace(diagnostic, backtrace));
     }
 
     #[track_caller]
@@ -1218,9 +1222,7 @@ impl DiagCtxt {
     }
 
     pub fn flush_delayed(&self) {
-        let mut inner = self.inner.borrow_mut();
+        self.inner.borrow_mut().flush_delayed(DelayedBugKind::Normal);
-        let bugs = std::mem::replace(&mut inner.span_delayed_bugs, Vec::new());
-        inner.flush_delayed(bugs, "no errors encountered even though `span_delayed_bug` issued");
     }
 }
 
@@ -1270,17 +1272,30 @@ impl DiagCtxtInner {
             return None;
         }
 
-        if diagnostic.level == DelayedBug {
+        // FIXME(eddyb) this should check for `has_errors` and stop pushing
-            // FIXME(eddyb) this should check for `has_errors` and stop pushing
+        // once *any* errors were emitted (and truncate `span_delayed_bugs`
-            // once *any* errors were emitted (and truncate `span_delayed_bugs`
+        // when an error is first emitted, also), but maybe there's a case
-            // when an error is first emitted, also), but maybe there's a case
+        // in which that's not sound? otherwise this is really inefficient.
-            // in which that's not sound? otherwise this is really inefficient.
+        match diagnostic.level {
-            let backtrace = std::backtrace::Backtrace::capture();
+            DelayedBug(_) if self.flags.eagerly_emit_delayed_bugs => {
-            self.span_delayed_bugs
+                diagnostic.level = Error;
-                .push(DelayedDiagnostic::with_backtrace(diagnostic.clone(), backtrace));
+            }
+            DelayedBug(DelayedBugKind::Normal) => {
+                let backtrace = std::backtrace::Backtrace::capture();
+                self.span_delayed_bugs
+                    .push(DelayedDiagnostic::with_backtrace(diagnostic.clone(), backtrace));
 
-            #[allow(deprecated)]
+                #[allow(deprecated)]
-            return Some(ErrorGuaranteed::unchecked_claim_error_was_emitted());
+                return Some(ErrorGuaranteed::unchecked_claim_error_was_emitted());
+            }
+            DelayedBug(DelayedBugKind::GoodPath) => {
+                let backtrace = std::backtrace::Backtrace::capture();
+                self.good_path_delayed_bugs
+                    .push(DelayedDiagnostic::with_backtrace(diagnostic.clone(), backtrace));
+
+                return None;
+            }
+            _ => {}
         }
 
         if diagnostic.has_future_breakage() {
@@ -1396,11 +1411,18 @@ impl DiagCtxtInner {
         self.emit_diagnostic(Diagnostic::new(FailureNote, msg));
     }
 
-    fn flush_delayed(
+    fn flush_delayed(&mut self, kind: DelayedBugKind) {
-        &mut self,
+        let (bugs, explanation) = match kind {
-        bugs: Vec<DelayedDiagnostic>,
+            DelayedBugKind::Normal => (
-        explanation: impl Into<DiagnosticMessage> + Copy,
+                std::mem::take(&mut self.span_delayed_bugs),
-    ) {
+                "no errors encountered even though `span_delayed_bug` issued",
+            ),
+            DelayedBugKind::GoodPath => (
+                std::mem::take(&mut self.good_path_delayed_bugs),
+                "no warnings or errors encountered even though `good_path_delayed_bugs` issued",
+            ),
+        };
+
         if bugs.is_empty() {
             return;
         }
@@ -1433,7 +1455,7 @@ impl DiagCtxtInner {
                 if backtrace || self.ice_file.is_none() { bug.decorate() } else { bug.inner };
 
             // "Undelay" the `DelayedBug`s (into plain `Bug`s).
-            if bug.level != DelayedBug {
+            if !matches!(bug.level, DelayedBug(_)) {
                 // NOTE(eddyb) not panicking here because we're already producing
                 // an ICE, and the more information the merrier.
                 bug.subdiagnostic(InvalidFlushedDelayedDiagnosticLevel {
@@ -1521,8 +1543,9 @@ pub enum Level {
     /// silently dropped. I.e. "expect other errors are emitted" semantics. Useful on code paths
     /// that should only be reached when compiling erroneous code.
     ///
-    /// Its `EmissionGuarantee` is `ErrorGuaranteed`.
+    /// Its `EmissionGuarantee` is `ErrorGuaranteed` for `Normal` delayed bugs, and `()` for
-    DelayedBug,
+    /// `GoodPath` delayed bugs.
+    DelayedBug(DelayedBugKind),
 
     /// An error that causes an immediate abort. Used for things like configuration errors,
     /// internal overflows, some file operation errors.
@@ -1597,7 +1620,7 @@ impl Level {
     fn color(self) -> ColorSpec {
         let mut spec = ColorSpec::new();
         match self {
-            Bug | DelayedBug | Fatal | Error => {
+            Bug | DelayedBug(_) | Fatal | Error => {
                 spec.set_fg(Some(Color::Red)).set_intense(true);
             }
             ForceWarning(_) | Warning => {
@@ -1617,7 +1640,7 @@ impl Level {
 
     pub fn to_str(self) -> &'static str {
         match self {
-            Bug | DelayedBug => "error: internal compiler error",
+            Bug | DelayedBug(_) => "error: internal compiler error",
             Fatal | Error => "error",
             ForceWarning(_) | Warning => "warning",
             Note | OnceNote => "note",

compiler/rustc_session/src/config.rs

@@ -1146,6 +1146,7 @@ impl UnstableOptions {
         DiagCtxtFlags {
             can_emit_warnings,
             treat_err_as_bug: self.treat_err_as_bug,
+            eagerly_emit_delayed_bugs: self.eagerly_emit_delayed_bugs,
             macro_backtrace: self.macro_backtrace,
             deduplicate_diagnostics: self.deduplicate_diagnostics,
             track_diagnostics: self.track_diagnostics,

compiler/rustc_session/src/options.rs

@@ -1583,6 +1583,9 @@ options! {
         "version of DWARF debug information to emit (default: 2 or 4, depending on platform)"),
     dylib_lto: bool = (false, parse_bool, [UNTRACKED],
         "enables LTO for dylib crate type"),
+    eagerly_emit_delayed_bugs: bool = (false, parse_bool, [UNTRACKED],
+        "emit delayed bugs eagerly as errors instead of stashing them and emitting \
+        them only if an error has not been emitted"),
     ehcont_guard: bool = (false, parse_bool, [TRACKED],
         "generate Windows EHCont Guard tables"),
     emit_stack_sizes: bool = (false, parse_bool, [UNTRACKED],

tests/ui/treat-err-as-bug/eagerly-emit.rs

@@ -0,0 +1,11 @@
+// compile-flags: -Zeagerly-emit-delayed-bugs
+
+trait Foo {}
+
+fn main() {}
+
+fn f() -> impl Foo {
+    //~^ ERROR the trait bound `i32: Foo` is not satisfied
+    //~| ERROR `report_selection_error` did not emit an error
+    1i32
+}

tests/ui/treat-err-as-bug/eagerly-emit.stderr

@@ -0,0 +1,28 @@
+error: `report_selection_error` did not emit an error
+  --> $DIR/eagerly-emit.rs:7:11
+   |
+LL | fn f() -> impl Foo {
+   |           ^^^^^^^^
+
+error: trimmed_def_paths constructed but no error emitted; use `DelayDm` for lints or `with_no_trimmed_paths` for debugging
+
+error[E0277]: the trait bound `i32: Foo` is not satisfied
+  --> $DIR/eagerly-emit.rs:7:11
+   |
+LL | fn f() -> impl Foo {
+   |           ^^^^^^^^ the trait `Foo` is not implemented for `i32`
+...
+LL |     1i32
+   |     ---- return type was inferred to be `i32` here
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/eagerly-emit.rs:3:1
+   |
+LL | trait Foo {}
+   | ^^^^^^^^^
+
+error: expected fulfillment errors
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0277`.