5 files changed, 115 insertions, 46 deletions
diff --git a/compiler/rustc_query_system/src/error.rs b/compiler/rustc_query_system/src/error.rs
new file mode 100644
index 00000000000..5f992ec9e21
--- /dev/null
+++ b/compiler/rustc_query_system/src/error.rs
@@ -0,0 +1,73 @@
+use rustc_errors::AddSubdiagnostic;
+use rustc_span::Span;
+
+pub struct CycleStack {
+    pub span: Span,
+    pub desc: String,
+}
+
+impl AddSubdiagnostic for CycleStack {
+    fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
+        diag.span_note(self.span, &format!("...which requires {}...", self.desc));
+    }
+}
+
+#[derive(SessionSubdiagnostic)]
+pub enum StackCount {
+    #[note(query_system::cycle_stack_single)]
+    Single,
+    #[note(query_system::cycle_stack_multiple)]
+    Multiple,
+}
+
+#[derive(SessionSubdiagnostic)]
+pub enum Alias {
+    #[note(query_system::cycle_recursive_ty_alias)]
+    #[help(query_system::cycle_recursive_ty_alias_help1)]
+    #[help(query_system::cycle_recursive_ty_alias_help2)]
+    Ty,
+    #[note(query_system::cycle_recursive_trait_alias)]
+    Trait,
+}
+
+#[derive(SessionSubdiagnostic)]
+#[note(query_system::cycle_usage)]
+pub struct CycleUsage {
+    #[primary_span]
+    pub span: Span,
+    pub usage: String,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(query_system::cycle, code = "E0391")]
+pub struct Cycle {
+    #[primary_span]
+    pub span: Span,
+    pub stack_bottom: String,
+    #[subdiagnostic]
+    pub cycle_stack: Vec<CycleStack>,
+    #[subdiagnostic]
+    pub stack_count: StackCount,
+    #[subdiagnostic]
+    pub alias: Option<Alias>,
+    #[subdiagnostic]
+    pub cycle_usage: Option<CycleUsage>,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(query_system::reentrant)]
+pub struct Reentrant;
+
+#[derive(SessionDiagnostic)]
+#[diag(query_system::increment_compilation)]
+#[help]
+#[note(query_system::increment_compilation_note1)]
+#[note(query_system::increment_compilation_note2)]
+pub struct IncrementCompilation {
+    pub run_cmd: String,
+    pub dep_node: String,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(query_system::query_overflow)]
+pub struct QueryOverflow;
diff --git a/compiler/rustc_query_system/src/lib.rs b/compiler/rustc_query_system/src/lib.rs
index 68284dcaa0b..7067bc5f09c 100644
--- a/compiler/rustc_query_system/src/lib.rs
+++ b/compiler/rustc_query_system/src/lib.rs
@@ -5,6 +5,8 @@
 #![feature(min_specialization)]
 #![feature(extern_types)]
 #![allow(rustc::potential_query_instability)]
+// #![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate tracing;
@@ -15,5 +17,6 @@ extern crate rustc_macros;
 
 pub mod cache;
 pub mod dep_graph;
+mod error;
 pub mod ich;
 pub mod query;
diff --git a/compiler/rustc_query_system/src/query/job.rs b/compiler/rustc_query_system/src/query/job.rs
index 6d2aff38172..ddb5cd06344 100644
--- a/compiler/rustc_query_system/src/query/job.rs
+++ b/compiler/rustc_query_system/src/query/job.rs
@@ -1,12 +1,11 @@
+use crate::error::CycleStack;
 use crate::query::plumbing::CycleError;
 use crate::query::{QueryContext, QueryStackFrame};
-use rustc_hir::def::DefKind;
 
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{
-    struct_span_err, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, Handler, Level,
-};
-use rustc_session::Session;
+use rustc_errors::{Diagnostic, DiagnosticBuilder, ErrorGuaranteed, Handler, Level};
+use rustc_hir::def::DefKind;
+use rustc_session::{Session, SessionDiagnostic};
 use rustc_span::Span;
 
 use std::hash::Hash;
@@ -536,46 +535,44 @@ pub(crate) fn report_cycle<'a>(
     assert!(!stack.is_empty());
 
     let span = stack[0].query.default_span(stack[1 % stack.len()].span);
-    let mut err =
-        struct_span_err!(sess, span, E0391, "cycle detected when {}", stack[0].query.description);
+
+    let mut cycle_stack = Vec::new();
+
+    use crate::error::StackCount;
+    let stack_count = if stack.len() == 1 { StackCount::Single } else { StackCount::Multiple };
 
     for i in 1..stack.len() {
         let query = &stack[i].query;
         let span = query.default_span(stack[(i + 1) % stack.len()].span);
-        err.span_note(span, &format!("...which requires {}...", query.description));
-    }
-
-    if stack.len() == 1 {
-        err.note(&format!("...which immediately requires {} again", stack[0].query.description));
-    } else {
-        err.note(&format!(
-            "...which again requires {}, completing the cycle",
-            stack[0].query.description
-        ));
-    }
-
-    if stack.iter().all(|entry| {
-        entry
-            .query
-            .def_kind
-            .map_or(false, |def_kind| matches!(def_kind, DefKind::TyAlias | DefKind::TraitAlias))
-    }) {
-        if stack.iter().all(|entry| {
-            entry.query.def_kind.map_or(false, |def_kind| matches!(def_kind, DefKind::TyAlias))
-        }) {
-            err.note("type aliases cannot be recursive");
-            err.help("consider using a struct, enum, or union instead to break the cycle");
-            err.help("see <https://doc.rust-lang.org/reference/types.html#recursive-types> for more information");
-        } else {
-            err.note("trait aliases cannot be recursive");
-        }
+        cycle_stack.push(CycleStack { span, desc: query.description.to_owned() });
     }
 
+    let mut cycle_usage = None;
     if let Some((span, query)) = usage {
-        err.span_note(query.default_span(span), &format!("cycle used when {}", query.description));
+        cycle_usage = Some(crate::error::CycleUsage {
+            span: query.default_span(span),
+            usage: query.description,
+        });
     }
 
-    err
+    let alias = if stack.iter().all(|entry| entry.query.def_kind == Some(DefKind::TyAlias)) {
+        Some(crate::error::Alias::Ty)
+    } else if stack.iter().all(|entry| entry.query.def_kind == Some(DefKind::TraitAlias)) {
+        Some(crate::error::Alias::Trait)
+    } else {
+        None
+    };
+
+    let cycle_diag = crate::error::Cycle {
+        span,
+        cycle_stack,
+        stack_bottom: stack[0].query.description.to_owned(),
+        alias,
+        cycle_usage: cycle_usage,
+        stack_count,
+    };
+
+    cycle_diag.into_diagnostic(&sess.parse_sess)
 }
 
 pub fn print_query_stack<CTX: QueryContext>(
diff --git a/compiler/rustc_query_system/src/query/mod.rs b/compiler/rustc_query_system/src/query/mod.rs
index a1f2b081d43..c6197b9fedb 100644
--- a/compiler/rustc_query_system/src/query/mod.rs
+++ b/compiler/rustc_query_system/src/query/mod.rs
@@ -125,6 +125,6 @@ pub trait QueryContext: HasDepContext {
     ) -> R;
 
     fn depth_limit_error(&self) {
-        self.dep_context().sess().fatal("queries overflow the depth limit!");
+        self.dep_context().sess().emit_fatal(crate::error::QueryOverflow);
     }
 }
diff --git a/compiler/rustc_query_system/src/query/plumbing.rs b/compiler/rustc_query_system/src/query/plumbing.rs
index 6ae9147ff77..e97411b777b 100644
--- a/compiler/rustc_query_system/src/query/plumbing.rs
+++ b/compiler/rustc_query_system/src/query/plumbing.rs
@@ -618,16 +618,12 @@ fn incremental_verify_ich_cold(sess: &Session, dep_node: DebugArg<'_>, result: D
     let old_in_panic = INSIDE_VERIFY_PANIC.with(|in_panic| in_panic.replace(true));
 
     if old_in_panic {
-        sess.struct_err(
-            "internal compiler error: re-entrant incremental verify failure, suppressing message",
-        )
-        .emit();
+        sess.emit_err(crate::error::Reentrant);
     } else {
-        sess.struct_err(&format!("internal compiler error: encountered incremental compilation error with {:?}", dep_node))
-                .help(&format!("This is a known issue with the compiler. Run {} to allow your project to compile", run_cmd))
-                .note("Please follow the instructions below to create a bug report with the provided information")
-                .note("See <https://github.com/rust-lang/rust/issues/84970> for more information")
-                .emit();
+        sess.emit_err(crate::error::IncrementCompilation {
+            run_cmd,
+            dep_node: format!("{:?}", dep_node),
+        });
         panic!("Found unstable fingerprints for {:?}: {:?}", dep_node, result);
     }