diff --git a/Cargo.lock b/Cargo.lock
index 85e5e6c97105c..f8e9fc88ac2e3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5367,10 +5367,14 @@ dependencies = [
  "cargo_metadata 0.19.1",
  "fluent-syntax",
  "ignore",
+ "md-5",
  "miropt-test-tools",
  "regex",
  "rustc-hash 2.1.0",
  "semver",
+ "serde",
+ "serde_derive",
+ "serde_json",
  "similar",
  "termcolor",
  "walkdir",
diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
index 3b7367d1ee209..289d3a63337e2 100644
--- a/compiler/rustc_ast/src/token.rs
+++ b/compiler/rustc_ast/src/token.rs
@@ -209,6 +209,7 @@ impl Lit {
         }
     }
 
+    // tidy-keep-sync-with=tidy-ticket-ast-from_token
     /// Keep this in sync with `Token::can_begin_literal_maybe_minus` excluding unary negation.
     pub fn from_token(token: &Token) -> Option<Lit> {
         match token.uninterpolate().kind {
@@ -223,6 +224,7 @@ impl Lit {
             _ => None,
         }
     }
+    // tidy-keep-sync-with=tidy-ticket-ast-from_token
 }
 
 impl fmt::Display for Lit {
@@ -748,6 +750,7 @@ impl Token {
     ///
     /// In other words, would this token be a valid start of `parse_literal_maybe_minus`?
     ///
+    // tidy-keep-sync-with=tidy-ticket-ast-can_begin_literal_maybe_minus
     /// Keep this in sync with and `Lit::from_token`, excluding unary negation.
     pub fn can_begin_literal_maybe_minus(&self) -> bool {
         match self.uninterpolate().kind {
@@ -774,6 +777,7 @@ impl Token {
             _ => false,
         }
     }
+    // tidy-keep-sync-with=tidy-ticket-ast-can_begin_literal_maybe_minus
 
     pub fn can_begin_string_literal(&self) -> bool {
         match self.uninterpolate().kind {
diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs
index bb9dc651cec25..e192ab748379f 100644
--- a/compiler/rustc_builtin_macros/src/assert/context.rs
+++ b/compiler/rustc_builtin_macros/src/assert/context.rs
@@ -291,6 +291,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
             }
             // Expressions that are not worth or can not be captured.
             //
+            // tidy-keep-sync-with=tidy-ticket-all-expr-kinds
             // Full list instead of `_` to catch possible future inclusions and to
             // sync with the `rfc-2011-nicer-assert-messages/all-expr-kinds.rs` test.
             ExprKind::Assign(_, _, _)
@@ -323,7 +324,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
             | ExprKind::Yeet(_)
             | ExprKind::Become(_)
             | ExprKind::Yield(_)
-            | ExprKind::UnsafeBinderCast(..) => {}
+            | ExprKind::UnsafeBinderCast(..) => {} // tidy-keep-sync-with=tidy-ticket-all-expr-kinds
         }
     }
 
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index b40bb4ed5d2ac..f63d0dd1381c7 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -742,6 +742,7 @@ impl<B: WriteBackendMethods> WorkItem<B> {
         }
     }
 
+    // tidy-keep-sync-with=tidy-ticket-short_description
     /// Generate a short description of this work item suitable for use as a thread name.
     fn short_description(&self) -> String {
         // `pthread_setname()` on *nix ignores anything beyond the first 15
@@ -789,6 +790,7 @@ impl<B: WriteBackendMethods> WorkItem<B> {
             WorkItem::LTO(m) => desc("lto", "LTO module", m.name()),
         }
     }
+    // tidy-keep-sync-with=tidy-ticket-short_description
 }
 
 /// A result produced by the backend.
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 1daa17fbaf347..0bf97093618ca 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -279,6 +279,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                         //
                         // This exception needs to be kept in sync with allowing
                         // `#[target_feature]` on `main` and `start`.
+                        // FIXME: sync me
                     } else if !tcx.features().target_feature_11() {
                         feature_err(
                             &tcx.sess,
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index d75df1ad4425b..0b21cd8be6084 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -707,6 +707,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                 interp_ok(true)
             }
             ty::Float(_) | ty::Int(_) | ty::Uint(_) => {
+                // tidy-keep-sync-with=tidy-ticket-try_visit_primitive
                 // NOTE: Keep this in sync with the array optimization for int/float
                 // types below!
                 self.read_scalar(
@@ -722,6 +723,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                     self.add_data_range_place(value);
                 }
                 interp_ok(true)
+                // tidy-keep-sync-with=tidy-ticket-try_visit_primitive
             }
             ty::RawPtr(..) => {
                 let place = self.deref_pointer(value, ExpectedKind::RawPtr)?;
@@ -1188,9 +1190,10 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
                     }
                 };
 
+                // tidy-keep-sync-with=tidy-ticket-visit_value
                 // Optimization: we just check the entire range at once.
                 // NOTE: Keep this in sync with the handling of integer and float
-                // types above, in `visit_primitive`.
+                // types above, in `try_visit_primitive`.
                 // No need for an alignment check here, this is not an actual memory access.
                 let alloc = self.ecx.get_ptr_alloc(mplace.ptr(), size)?.expect("we already excluded size 0");
 
@@ -1230,6 +1233,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
                     // Also, mark this as containing data, not padding.
                     self.add_data_range(mplace.ptr(), size);
                 }
+                // tidy-keep-sync-with=tidy-ticket-visit_value
             }
             // Fast path for arrays and slices of ZSTs. We only need to check a single ZST element
             // of an array and not all of them, because there's only a single value of a specific
diff --git a/compiler/rustc_data_structures/src/profiling.rs b/compiler/rustc_data_structures/src/profiling.rs
index 19050746c2f18..3cb52c79c974e 100644
--- a/compiler/rustc_data_structures/src/profiling.rs
+++ b/compiler/rustc_data_structures/src/profiling.rs
@@ -126,6 +126,7 @@ bitflags::bitflags! {
     }
 }
 
+// tidy-keep-sync-with=tidy-ticket-self-profile-events
 // keep this in sync with the `-Z self-profile-events` help message in rustc_session/options.rs
 const EVENT_FILTERS_BY_NAME: &[(&str, EventFilter)] = &[
     ("none", EventFilter::empty()),
@@ -143,6 +144,7 @@ const EVENT_FILTERS_BY_NAME: &[(&str, EventFilter)] = &[
     ("incr-result-hashing", EventFilter::INCR_RESULT_HASHING),
     ("artifact-sizes", EventFilter::ARTIFACT_SIZES),
 ];
+// tidy-keep-sync-with=tidy-ticket-self-profile-events
 
 /// Something that uniquely identifies a query invocation.
 pub struct QueryInvocationId(pub u32);
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index f938352820df7..e5855404a449c 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -3188,6 +3188,7 @@ fn num_decimal_digits(num: usize) -> usize {
 
 // We replace some characters so the CLI output is always consistent and underlines aligned.
 // Keep the following list in sync with `rustc_span::char_width`.
+// FIXME: sync me
 const OUTPUT_REPLACEMENTS: &[(char, &str)] = &[
     // In terminals without Unicode support the following will be garbled, but in *all* terminals
     // the underlying codepoint will be as well. We could gate this replacement behind a "unicode
diff --git a/compiler/rustc_errors/src/json.rs b/compiler/rustc_errors/src/json.rs
index 97df7f9265aa4..fc3bafaf07ec1 100644
--- a/compiler/rustc_errors/src/json.rs
+++ b/compiler/rustc_errors/src/json.rs
@@ -275,6 +275,8 @@ struct FutureIncompatReport<'a> {
     future_incompat_report: Vec<FutureBreakageItem<'a>>,
 }
 
+// tidy-keep-sync-with=tidy-ticket-UnusedExterns
+// FIXME: where it located in cargo?
 // NOTE: Keep this in sync with the equivalent structs in rustdoc's
 // doctest component (as well as cargo).
 // We could unify this struct the one in rustdoc but they have different
@@ -286,6 +288,7 @@ struct UnusedExterns<'a> {
     /// List of unused externs by their names.
     unused_extern_names: &'a [&'a str],
 }
+// tidy-keep-sync-with=tidy-ticket-UnusedExterns
 
 impl Diagnostic {
     /// Converts from `rustc_errors::DiagInner` to `Diagnostic`.
diff --git a/compiler/rustc_hir_analysis/src/check/region.rs b/compiler/rustc_hir_analysis/src/check/region.rs
index 83c69dc2ef415..0629b740d3366 100644
--- a/compiler/rustc_hir_analysis/src/check/region.rs
+++ b/compiler/rustc_hir_analysis/src/check/region.rs
@@ -116,6 +116,7 @@ fn resolve_block<'tcx>(visitor: &mut ScopeResolutionVisitor<'tcx>, blk: &'tcx hi
     visitor.cx.var_parent = visitor.cx.parent;
 
     {
+        // FIXME: sync with exactly where?
         // This block should be kept approximately in sync with
         // `intravisit::walk_block`. (We manually walk the block, rather
         // than call `walk_block`, in order to maintain precise
diff --git a/compiler/rustc_metadata/src/native_libs.rs b/compiler/rustc_metadata/src/native_libs.rs
index 2a1e4b261e737..05c5baff69be5 100644
--- a/compiler/rustc_metadata/src/native_libs.rs
+++ b/compiler/rustc_metadata/src/native_libs.rs
@@ -48,6 +48,7 @@ pub fn walk_native_lib_search_dirs<R>(
         f(&sess.target_tlib_path.dir.join("self-contained"), false)?;
     }
 
+    // tidy-keep-sync-with=tidy-ticket-copy_third_party_objects
     // Toolchains for some targets may ship `libunwind.a`, but place it into the main sysroot
     // library directory instead of the self-contained directories.
     // Sanitizer libraries have the same issue and are also linked by name on Apple targets.
@@ -76,6 +77,7 @@ pub fn walk_native_lib_search_dirs<R>(
     }
 
     ControlFlow::Continue(())
+    // tidy-keep-sync-with=tidy-ticket-copy_third_party_objects
 }
 
 pub fn try_find_native_static_library(
diff --git a/compiler/rustc_middle/src/dep_graph/dep_node.rs b/compiler/rustc_middle/src/dep_graph/dep_node.rs
index fcfc31575f8aa..14b8bed3172bf 100644
--- a/compiler/rustc_middle/src/dep_graph/dep_node.rs
+++ b/compiler/rustc_middle/src/dep_graph/dep_node.rs
@@ -86,6 +86,7 @@ macro_rules! define_dep_nodes {
         // struct, and there we can take advantage of the unused bits in the u16.
         #[allow(non_camel_case_types)]
         #[repr(u16)] // Must be kept in sync with the inner type of `DepKind`.
+        // FIXME: sync me
         enum DepKindDefs {
             $( $( #[$attr] )* $variant),*
         }
@@ -96,6 +97,7 @@ macro_rules! define_dep_nodes {
 
             $(
                 // The `as u16` cast must be kept in sync with the inner type of `DepKind`.
+                // FIXME: sync me
                 pub const $variant: DepKind = DepKind::new(DepKindDefs::$variant as u16);
             )*
         }
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index 473b817aed076..b8f2bee210419 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -135,11 +135,13 @@ impl UnwindAction {
 
 impl UnwindTerminateReason {
     pub fn as_str(self) -> &'static str {
+        // tidy-keep-sync-with=tidy-tidy-ticket-panic-message
         // Keep this in sync with the messages in `core/src/panicking.rs`.
         match self {
             UnwindTerminateReason::Abi => "panic in a function that cannot unwind",
             UnwindTerminateReason::InCleanup => "panic in a destructor during cleanup",
         }
+        // tidy-keep-sync-with=tidy-tidy-ticket-panic-message
     }
 
     /// A short representation of this used for MIR printing.
@@ -304,6 +306,7 @@ impl<O> AssertKind<O> {
     /// `AssertKind::panic_function` and the lang items mentioned in its docs).
     /// Note that we deliberately show more details here than we do at runtime, such as the actual
     /// numbers that overflowed -- it is much easier to do so here than at runtime.
+    // FIXME: sync me
     pub fn diagnostic_message(&self) -> DiagMessage {
         use AssertKind::*;
 
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index e4ded2c30f539..8dac550f7bd15 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -900,6 +900,7 @@ impl<'tcx> Instance<'tcx> {
 
     #[inline(always)]
     // Keep me in sync with try_instantiate_mir_and_normalize_erasing_regions
+    // FIXME: sync me
     pub fn instantiate_mir_and_normalize_erasing_regions<T>(
         &self,
         tcx: TyCtxt<'tcx>,
@@ -918,6 +919,7 @@ impl<'tcx> Instance<'tcx> {
 
     #[inline(always)]
     // Keep me in sync with instantiate_mir_and_normalize_erasing_regions
+    // FIXME: sync me
     pub fn try_instantiate_mir_and_normalize_erasing_regions<T>(
         &self,
         tcx: TyCtxt<'tcx>,
diff --git a/compiler/rustc_middle/src/ty/predicate.rs b/compiler/rustc_middle/src/ty/predicate.rs
index 32d6455e82557..d55c9b8376025 100644
--- a/compiler/rustc_middle/src/ty/predicate.rs
+++ b/compiler/rustc_middle/src/ty/predicate.rs
@@ -138,6 +138,7 @@ impl<'tcx> Predicate<'tcx> {
     /// unsoundly accept some programs. See #91068.
     #[inline]
     pub fn allow_normalization(self) -> bool {
+        // FIXME: sync me
         // Keep this in sync with the one in `rustc_type_ir::inherent`!
         match self.kind().skip_binder() {
             PredicateKind::Clause(ClauseKind::WellFormed(_))
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 75893da0e5836..799a149904517 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -693,6 +693,7 @@ impl<'tcx> TyCtxt<'tcx> {
             && !self.is_foreign_item(def_id)
     }
 
+    // tidy-keep-sync-with=tidy-ticket-thread_local_ptr_ty
     /// Returns the type a reference to the thread local takes in MIR.
     pub fn thread_local_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
         let static_ty = self.type_of(def_id).instantiate_identity();
@@ -705,6 +706,7 @@ impl<'tcx> TyCtxt<'tcx> {
             Ty::new_imm_ref(self, self.lifetimes.re_static, static_ty)
         }
     }
+    // tidy-keep-sync-with=tidy-ticket-thread_local_ptr_ty
 
     /// Get the type of the pointer to the static that we use in MIR.
     pub fn static_ptr_ty(self, def_id: DefId, typing_env: ty::TypingEnv<'tcx>) -> Ty<'tcx> {
@@ -712,7 +714,9 @@ impl<'tcx> TyCtxt<'tcx> {
         let static_ty =
             self.normalize_erasing_regions(typing_env, self.type_of(def_id).instantiate_identity());
 
+        // tidy-keep-sync-with=tidy-ticket-static_ptr_ty
         // Make sure that accesses to unsafe statics end up using raw pointers.
+        // FIXME: should it said sync with thread_local_ptr_ty?
         // For thread-locals, this needs to be kept in sync with `Rvalue::ty`.
         if self.is_mutable_static(def_id) {
             Ty::new_mut_ptr(self, static_ty)
@@ -721,6 +725,7 @@ impl<'tcx> TyCtxt<'tcx> {
         } else {
             Ty::new_imm_ref(self, self.lifetimes.re_erased, static_ty)
         }
+        // tidy-keep-sync-with=tidy-ticket-static_ptr_ty
     }
 
     /// Return the set of types that should be taken into account when checking
diff --git a/compiler/rustc_mir_transform/src/coverage/query.rs b/compiler/rustc_mir_transform/src/coverage/query.rs
index 3e7cf8541c23a..80bf6a50d45fb 100644
--- a/compiler/rustc_mir_transform/src/coverage/query.rs
+++ b/compiler/rustc_mir_transform/src/coverage/query.rs
@@ -109,6 +109,7 @@ fn coverage_ids_info<'tcx>(
         // to any particular point in the control-flow graph.
         // (Keep this in sync with the injection of `ExpressionUsed`
         // statements in the `InstrumentCoverage` MIR pass.)
+        // FIXME: sync me
         if let MappingKind::Code(CovTerm::Expression(id)) = mapping.kind {
             expressions_seen.remove(id);
         }
diff --git a/compiler/rustc_mir_transform/src/mentioned_items.rs b/compiler/rustc_mir_transform/src/mentioned_items.rs
index cf5c5f85a9ff6..de3a1375e1b72 100644
--- a/compiler/rustc_mir_transform/src/mentioned_items.rs
+++ b/compiler/rustc_mir_transform/src/mentioned_items.rs
@@ -33,6 +33,7 @@ impl<'tcx> crate::MirPass<'tcx> for MentionedItems {
 // visiting the exact same places but then instead of monomorphizing and creating `MonoItems`, we
 // have to remain generic and just recording the relevant information in `mentioned_items`, where it
 // will then be monomorphized later during "mentioned items" collection.
+// FIXME: sync me
 impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> {
     fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) {
         self.super_terminator(terminator, location);
diff --git a/compiler/rustc_monomorphize/src/partitioning.rs b/compiler/rustc_monomorphize/src/partitioning.rs
index 7b17966343084..b626eae027583 100644
--- a/compiler/rustc_monomorphize/src/partitioning.rs
+++ b/compiler/rustc_monomorphize/src/partitioning.rs
@@ -488,6 +488,8 @@ fn merge_codegen_units<'tcx>(
         codegen_units.sort_by_key(|cgu| cmp::Reverse(cgu.size_estimate()));
         let num_digits = codegen_units.len().ilog10() as usize + 1;
         for (index, cgu) in codegen_units.iter_mut().enumerate() {
+            // tidy-keep-sync-with=tidy-ticket-short_description
+            // FIXME: is it sync?
             // Note: `WorkItem::short_description` depends on this name ending
             // with `-cgu.` followed by a numeric suffix. Please keep it in
             // sync with this code.
@@ -495,6 +497,7 @@ fn merge_codegen_units<'tcx>(
             let numbered_codegen_unit_name =
                 cgu_name_builder.build_cgu_name_no_mangle(LOCAL_CRATE, &["cgu"], Some(suffix));
             cgu.set_name(numbered_codegen_unit_name);
+            // tidy-keep-sync-with=tidy-ticket-short_description
         }
     }
 }
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
index 3c5d9b95e772d..cf8c23ac0f3a2 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
@@ -255,6 +255,7 @@ where
     }
 }
 
+// tidy-keep-sync-with=tidy-ticket-extract_tupled_inputs_and_output_from_callable
 // Returns a binder of the tupled inputs types and output type from a builtin callable type.
 pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<I: Interner>(
     cx: I,
@@ -393,6 +394,7 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<I: Intern
         }
     }
 }
+// tidy-keep-sync-with=tidy-ticket-extract_tupled_inputs_and_output_from_callable
 
 /// Relevant types for an async callable, including its inputs, output,
 /// and the return type you get from awaiting the output.
@@ -712,6 +714,7 @@ pub(in crate::solve) fn extract_fn_def_from_const_callable<I: Interner>(
     }
 }
 
+// tidy-keep-sync-with=tidy-ticket-evaluate_host_effect_for_destruct_goal
 // NOTE: Keep this in sync with `evaluate_host_effect_for_destruct_goal` in
 // the old solver, for as long as that exists.
 pub(in crate::solve) fn const_conditions_for_destruct<I: Interner>(
@@ -789,6 +792,7 @@ pub(in crate::solve) fn const_conditions_for_destruct<I: Interner>(
         }
     }
 }
+// tidy-keep-sync-with=tidy-ticket-evaluate_host_effect_for_destruct_goal
 
 /// Assemble a list of predicates that would be present on a theoretical
 /// user impl for an object type. These predicates must be checked any time
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 7533e75ffe261..731ef29bd17e9 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -2181,6 +2181,7 @@ impl<'a> Parser<'a> {
         }
     }
 
+    // tidy-keep-sync-with=tidy-ticket-rustc_parse-can_begin_literal_maybe_minus
     /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
     /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
     pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
@@ -2216,6 +2217,7 @@ impl<'a> Parser<'a> {
             Ok(expr)
         }
     }
+    // tidy-keep-sync-with=tidy-ticket-rustc_parse-can_begin_literal_maybe_minus
 
     fn is_array_like_block(&mut self) -> bool {
         self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs
index 4ce868f014f42..d7b59d9b4629d 100644
--- a/compiler/rustc_pattern_analysis/src/constructor.rs
+++ b/compiler/rustc_pattern_analysis/src/constructor.rs
@@ -782,11 +782,14 @@ impl<Cx: PatCx> Constructor<Cx> {
         }
     }
 
+    // tidy-keep-sync-with=tidy-ticket-arity
     /// The number of fields for this constructor. This must be kept in sync with
     /// `Fields::wildcards`.
+    // FIXME: this comment long ago desynced
     pub(crate) fn arity(&self, cx: &Cx, ty: &Cx::Ty) -> usize {
         cx.ctor_arity(self, ty)
     }
+    // tidy-keep-sync-with=tidy-ticket-arity
 
     /// Returns whether `self` is covered by `other`, i.e. whether `self` is a subset of `other`.
     /// For the simple cases, this is simply checking for equality. For the "grouped" constructors,
diff --git a/compiler/rustc_session/src/config/cfg.rs b/compiler/rustc_session/src/config/cfg.rs
index d586f913335e0..df1cf62a6f6eb 100644
--- a/compiler/rustc_session/src/config/cfg.rs
+++ b/compiler/rustc_session/src/config/cfg.rs
@@ -176,6 +176,7 @@ pub(crate) fn default_configuration(sess: &Session) -> Cfg {
     //
     // NOTE: These insertions should be kept in sync with
     // `CheckCfg::fill_well_known` below.
+    // FIXME: sync me
 
     if sess.opts.debug_assertions {
         ins_none!(sym::debug_assertions);
@@ -334,6 +335,7 @@ impl CheckCfg {
         // The exceptions are where control flow forces things out of order.
         //
         // NOTE: This should be kept in sync with `default_configuration`.
+        // FIXME: what exactly sync there?
         // Note that symbols inserted conditionally in `default_configuration`
         // are inserted unconditionally here.
         //
diff --git a/compiler/rustc_session/src/config/sigpipe.rs b/compiler/rustc_session/src/config/sigpipe.rs
index 1830ee034855b..c08c5534777a7 100644
--- a/compiler/rustc_session/src/config/sigpipe.rs
+++ b/compiler/rustc_session/src/config/sigpipe.rs
@@ -1,3 +1,4 @@
+// tidy-keep-sync-with=tidy-ticket-sigpipe
 //! NOTE: Keep these constants in sync with `library/std/src/sys/pal/unix/mod.rs`!
 
 /// The default value if `-Zon-broken-pipe=...` is not specified. This resolves
@@ -23,3 +24,4 @@ pub const SIG_IGN: u8 = 2;
 /// such as `head -n 1`.
 #[allow(dead_code)]
 pub const SIG_DFL: u8 = 3;
+// tidy-keep-sync-with=tidy-ticket-sigpipe
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 3af6df6301774..42edbc1c0bf36 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -2095,12 +2095,14 @@ written to standard error output)"),
         `instructions:u` (retired instructions, userspace-only)
         `instructions-minus-irqs:u` (subtracting hardware interrupt counts for extra accuracy)"
     ),
-    /// keep this in sync with the event filter names in librustc_data_structures/profiling.rs
+    // tidy-keep-sync-with=tidy-ticket-self-profile-events
+    /// keep this in sync with the event filter names in rustc_data_structures/src/profiling.rs
     self_profile_events: Option<Vec<String>> = (None, parse_opt_comma_list, [UNTRACKED],
         "specify the events recorded by the self profiler;
         for example: `-Z self-profile-events=default,query-keys`
-        all options: none, all, default, generic-activity, query-provider, query-cache-hit
-                     query-blocked, incr-cache-load, incr-result-hashing, query-keys, function-args, args, llvm, artifact-sizes"),
+        all options: none, all, default, generic-activity, query-provider, query-cache-hit,
+                     query-blocked, incr-cache-load, query-keys, function-args, args, llvm, incr-result-hashing, artifact-sizes"),
+    // tidy-keep-sync-with=tidy-ticket-self-profile-events
     share_generics: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "make the current crate share its generic instantiations"),
     shell_argfiles: bool = (false, parse_bool, [UNTRACKED],
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index 51cfbf594716c..94982ed9e7436 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -2210,6 +2210,7 @@ pub fn char_width(ch: char) -> usize {
         // Keep the following list in sync with `rustc_errors::emitter::OUTPUT_REPLACEMENTS`. These
         // are control points that we replace before printing with a visible codepoint for the sake
         // of being able to point at them with underlines.
+        // FIXME: sync me
         '\u{0000}' | '\u{0001}' | '\u{0002}' | '\u{0003}' | '\u{0004}' | '\u{0005}'
         | '\u{0006}' | '\u{0007}' | '\u{0008}' | '\u{000B}' | '\u{000C}' | '\u{000D}'
         | '\u{000E}' | '\u{000F}' | '\u{0010}' | '\u{0011}' | '\u{0012}' | '\u{0013}'
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index d2abd881c4591..87939f46e573a 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -439,6 +439,7 @@ fn virtual_call_violations_for_method<'tcx>(
         } else {
             // We confirm that the `receiver_is_dispatchable` is accurate later,
             // see `check_receiver_correct`. It should be kept in sync with this code.
+            // FIXME: sync me
         }
     }
 
diff --git a/compiler/rustc_trait_selection/src/traits/effects.rs b/compiler/rustc_trait_selection/src/traits/effects.rs
index b32909efe0be7..204e8f717aecc 100644
--- a/compiler/rustc_trait_selection/src/traits/effects.rs
+++ b/compiler/rustc_trait_selection/src/traits/effects.rs
@@ -244,6 +244,7 @@ fn evaluate_host_effect_from_builtin_impls<'tcx>(
     }
 }
 
+// tidy-keep-sync-with=tidy-ticket-evaluate_host_effect_for_destruct_goal
 // NOTE: Keep this in sync with `const_conditions_for_destruct` in the new solver.
 fn evaluate_host_effect_for_destruct_goal<'tcx>(
     selcx: &mut SelectionContext<'_, 'tcx>,
@@ -331,6 +332,7 @@ fn evaluate_host_effect_for_destruct_goal<'tcx>(
         })
         .collect())
 }
+// tidy-keep-sync-with=tidy-ticket-evaluate_host_effect_for_destruct_goal
 
 fn evaluate_host_effect_from_selection_candiate<'tcx>(
     selcx: &mut SelectionContext<'_, 'tcx>,
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index aae0e34ddf393..ca4b1721f5d90 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -927,6 +927,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
         };
 
         let eligible = match &impl_source {
+            // tidy-keep-sync-with=tidy-ticket-assemble_candidates_from_impls-UserDefined
             ImplSource::UserDefined(impl_data) => {
                 // We have to be careful when projecting out of an
                 // impl because of specialization. If we are not in
@@ -991,6 +992,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                     Err(ErrorGuaranteed { .. }) => true,
                 }
             }
+            // tidy-keep-sync-with=tidy-ticket-assemble_candidates_from_impls-UserDefined
             ImplSource::Builtin(BuiltinImplSource::Misc, _) => {
                 // While a builtin impl may be known to exist, the associated type may not yet
                 // be known. Any type with multiple potential associated types is therefore
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 968dc631e50e5..020bf94cfe9c8 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -502,6 +502,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         }
     }
 
+    // tidy-keep-sync-with=tidy-ticket-assemble_fn_pointer_candidates
     /// Implements one of the `Fn()` family for a fn pointer.
     fn assemble_fn_pointer_candidates(
         &mut self,
@@ -541,6 +542,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             _ => {}
         }
     }
+    // tidy-keep-sync-with=tidy-ticket-assemble_fn_pointer_candidates
 
     /// Searches for impls that might apply to `obligation`.
     #[instrument(level = "debug", skip(self, candidates))]
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index fc76a86f79772..6db312bf8bac8 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -117,6 +117,7 @@ fn resolve_associated_item<'tcx>(
     // Now that we know which impl is being used, we can dispatch to
     // the actual function:
     Ok(match vtbl {
+        // tidy-keep-sync-with=tidy-ticket-resolve_associated_item-UserDefined
         traits::ImplSource::UserDefined(impl_data) => {
             debug!(
                 "resolving ImplSource::UserDefined: {:?}, {:?}, {:?}, {:?}",
@@ -230,6 +231,7 @@ fn resolve_associated_item<'tcx>(
 
             Some(ty::Instance::new(leaf_def.item.def_id, args))
         }
+        // tidy-keep-sync-with=tidy-ticket-resolve_associated_item-UserDefined
         traits::ImplSource::Builtin(BuiltinImplSource::Object(_), _) => {
             let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_args);
             if trait_ref.has_non_region_infer() || trait_ref.has_non_region_param() {
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index 1b5e44a913467..045d5cabc6b3d 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -226,6 +226,7 @@ pub use thin::ThinBox;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_insignificant_dtor]
 #[doc(search_unbox)]
+// FIXME: Sync with what?
 // The declaration of the `Box` struct must be kept in sync with the
 // compiler or ICEs will happen.
 pub struct Box<
diff --git a/library/core/src/panicking.rs b/library/core/src/panicking.rs
index 53e2b238bae69..6aea0e8a083f2 100644
--- a/library/core/src/panicking.rs
+++ b/library/core/src/panicking.rs
@@ -303,8 +303,10 @@ fn panic_misaligned_pointer_dereference(required: usize, found: usize) -> ! {
 #[lang = "panic_cannot_unwind"] // needed by codegen for panic in nounwind function
 #[rustc_nounwind]
 fn panic_cannot_unwind() -> ! {
+    // tidy-keep-sync-with=tidy-ticket-panic-message-nounwind
     // Keep the text in sync with `UnwindTerminateReason::as_str` in `rustc_middle`.
     panic_nounwind("panic in a function that cannot unwind")
+    // tidy-keep-sync-with=tidy-ticket-panic-message-nounwind
 }
 
 /// Panics because we are unwinding out of a destructor during cleanup.
@@ -319,8 +321,10 @@ fn panic_cannot_unwind() -> ! {
 #[lang = "panic_in_cleanup"] // needed by codegen for panic in nounwind function
 #[rustc_nounwind]
 fn panic_in_cleanup() -> ! {
+    // tidy-keep-sync-with=tidy-ticket-panic-message-nobacktrace
     // Keep the text in sync with `UnwindTerminateReason::as_str` in `rustc_middle`.
     panic_nounwind_nobacktrace("panic in a destructor during cleanup")
+    // tidy-keep-sync-with=tidy-ticket-panic-message-nobacktrace
 }
 
 /// This function is used instead of panic_fmt in const eval.
diff --git a/library/core/src/ptr/metadata.rs b/library/core/src/ptr/metadata.rs
index e93b5658e2436..869f699bbc382 100644
--- a/library/core/src/ptr/metadata.rs
+++ b/library/core/src/ptr/metadata.rs
@@ -58,10 +58,12 @@ use crate::ptr::NonNull;
 pub trait Pointee {
     /// The type for metadata in pointers and references to `Self`.
     #[lang = "metadata_type"]
+    // tidy-keep-sync-with=tidy-ticket-static_assert_expected_bounds_for_metadata
     // NOTE: Keep trait bounds in `static_assert_expected_bounds_for_metadata`
-    // in `library/core/src/ptr/metadata.rs`
+    // in `library/core/tests/ptr.rs`
     // in sync with those here:
     type Metadata: fmt::Debug + Copy + Send + Sync + Ord + Hash + Unpin + Freeze;
+    // tidy-keep-sync-with=tidy-ticket-static_assert_expected_bounds_for_metadata
 }
 
 /// Pointers to types implementing this trait alias are “thin”.
diff --git a/library/core/tests/ptr.rs b/library/core/tests/ptr.rs
index 7cefb615d0371..dec89c0f0c60e 100644
--- a/library/core/tests/ptr.rs
+++ b/library/core/tests/ptr.rs
@@ -586,12 +586,15 @@ fn ptr_metadata_bounds() {
         let _ = static_assert_expected_bounds_for_metadata::<<T as Pointee>::Metadata>;
     }
 
+    // tidy-keep-sync-with=tidy-ticket-static_assert_expected_bounds_for_metadata
+    // FIXME: should be core::hash::hash?
     fn static_assert_expected_bounds_for_metadata<Meta>()
     where
         // Keep this in sync with the associated type in `library/core/src/ptr/metadata.rs`
         Meta: Debug + Copy + Send + Sync + Ord + std::hash::Hash + Unpin + Freeze,
     {
     }
+    // tidy-keep-sync-with=tidy-ticket-static_assert_expected_bounds_for_metadata
 }
 
 #[test]
diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs
index 3cc1cae8d000e..4ca6f3a9c56ac 100644
--- a/library/std/src/sys/pal/unix/mod.rs
+++ b/library/std/src/sys/pal/unix/mod.rs
@@ -170,6 +170,7 @@ pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
             target_vendor = "unikraft",
         )))]
         {
+            // tidy-keep-sync-with=tidy-ticket-sigpipe
             // We don't want to add this as a public type to std, nor do we
             // want to `include!` a file from the compiler (which would break
             // Miri and xargo for example), so we choose to duplicate these
@@ -182,6 +183,7 @@ pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
                 pub const SIG_IGN: u8 = 2;
                 pub const SIG_DFL: u8 = 3;
             }
+            // tidy-keep-sync-with=tidy-ticket-sigpipe
 
             let (sigpipe_attr_specified, handler) = match sigpipe {
                 sigpipe::DEFAULT => (false, Some(libc::SIG_IGN)),
diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
index 4c4df922b3799..1d8b73f8983f9 100644
--- a/src/bootstrap/src/core/build_steps/compile.rs
+++ b/src/bootstrap/src/core/build_steps/compile.rs
@@ -291,6 +291,7 @@ fn copy_llvm_libunwind(builder: &Builder<'_>, target: TargetSelection, libdir: &
     libunwind_target
 }
 
+// tidy-keep-sync-with=tidy-ticket-copy_third_party_objects
 /// Copies third party objects needed by various targets.
 fn copy_third_party_objects(
     builder: &Builder<'_>,
@@ -320,6 +321,7 @@ fn copy_third_party_objects(
 
     target_deps
 }
+// tidy-keep-sync-with=tidy-ticket-copy_third_party_objects
 
 /// Copies third party objects needed by various targets for self-contained linkage.
 fn copy_self_contained_objects(
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 026380a46c685..4df260a3c9d7c 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -1462,6 +1462,7 @@ impl Config {
             // Allows creating alias for profile names, allowing
             // profiles to be renamed while maintaining back compatibility
             // Keep in sync with `profile_aliases` in bootstrap.py
+            // FIXME: sync me
             let profile_aliases = HashMap::from([("user", "dist")]);
             let include = match profile_aliases.get(include.as_str()) {
                 Some(alias) => alias,
diff --git a/src/bootstrap/src/core/download.rs b/src/bootstrap/src/core/download.rs
index c477bdb829a91..5f7f75f7efa9e 100644
--- a/src/bootstrap/src/core/download.rs
+++ b/src/bootstrap/src/core/download.rs
@@ -231,6 +231,7 @@ impl Config {
         // options should be kept in sync with
         // src/bootstrap/src/core/download.rs
         // for consistency
+        // FIXME: sync with what?
         let mut curl = command("curl");
         curl.args([
             // follow redirect
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index ebe2c332258d7..a3da70a230516 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -644,6 +644,8 @@ impl Build {
             features.push("llvm");
         }
         // keep in sync with `bootstrap/compile.rs:rustc_cargo_env`
+        // FIXME: this comment is leftover from https://github.com/rust-lang/rust/pull/93787,
+        // remove it?
         if self.config.rust_randomize_layout {
             features.push("rustc_randomized_layouts");
         }
diff --git a/src/bootstrap/src/utils/render_tests.rs b/src/bootstrap/src/utils/render_tests.rs
index 42b444464e527..18ced1809b14a 100644
--- a/src/bootstrap/src/utils/render_tests.rs
+++ b/src/bootstrap/src/utils/render_tests.rs
@@ -167,6 +167,7 @@ impl<'a> Renderer<'a> {
         if let Outcome::Ignored { reason } = outcome {
             self.ignored_tests += 1;
             // Keep this in sync with the "up-to-date" ignore message inserted by compiletest.
+            // FIXME: sync me
             if reason == Some("up-to-date") {
                 self.up_to_date_tests += 1;
             }
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 0dda3466a7173..828228946c742 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -335,10 +335,12 @@ pub(crate) fn run_global_ctxt(
     // typeck function bodies or run the default rustc lints.
     // (see `override_queries` in the `config`)
 
+    // tidy-keep-sync-with=tidy-ticket-sess-time-item_types_checking
     // NOTE: These are copy/pasted from typeck/lib.rs and should be kept in sync with those changes.
     let _ = tcx.sess.time("wf_checking", || {
         tcx.hir().try_par_for_each_module(|module| tcx.ensure().check_mod_type_wf(module))
     });
+    // tidy-keep-sync-with=tidy-ticket-sess-time-item_types_checking
 
     tcx.dcx().abort_if_errors();
 
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 009e9662933ae..a55cfda527bc1 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -439,6 +439,7 @@ impl DirState {
     }
 }
 
+// tidy-keep-sync-with=tidy-ticket-UnusedExterns
 // NOTE: Keep this in sync with the equivalent structs in rustc
 // and cargo.
 // We could unify this struct the one in rustc but they have different
@@ -450,6 +451,7 @@ pub(crate) struct UnusedExterns {
     /// List of unused externs by their names.
     unused_extern_names: Vec<String>,
 }
+// tidy-keep-sync-with=tidy-ticket-UnusedExterns
 
 fn add_exe_suffix(input: String, target: &TargetTuple) -> String {
     let exe_suffix = match target {
diff --git a/src/tools/tidy/Cargo.toml b/src/tools/tidy/Cargo.toml
index 2f424a482b5bb..973122621b781 100644
--- a/src/tools/tidy/Cargo.toml
+++ b/src/tools/tidy/Cargo.toml
@@ -16,6 +16,10 @@ termcolor = "1.1.3"
 rustc-hash = "2.0.0"
 fluent-syntax = "0.11.1"
 similar = "2.5.0"
+md-5 = "0.10"
+serde = "1"
+serde_derive = "1"
+serde_json = "1"
 
 [[bin]]
 name = "rust-tidy"
diff --git a/src/tools/tidy/src/lib.rs b/src/tools/tidy/src/lib.rs
index 1e7eb82b83e98..243893fab1f47 100644
--- a/src/tools/tidy/src/lib.rs
+++ b/src/tools/tidy/src/lib.rs
@@ -93,4 +93,5 @@ pub mod unit_tests;
 pub mod unknown_revision;
 pub mod unstable_book;
 pub mod walk;
+pub mod watcher;
 pub mod x_version;
diff --git a/src/tools/tidy/src/main.rs b/src/tools/tidy/src/main.rs
index 13a558fea48ea..04b04b986648f 100644
--- a/src/tools/tidy/src/main.rs
+++ b/src/tools/tidy/src/main.rs
@@ -146,6 +146,8 @@ fn main() {
 
         check!(x_version, &root_path, &cargo);
 
+        check!(watcher, &root_path, bless);
+
         let collected = {
             drain_handles(&mut handles);
 
diff --git a/src/tools/tidy/src/watcher.rs b/src/tools/tidy/src/watcher.rs
new file mode 100644
index 0000000000000..9e5a255d9202d
--- /dev/null
+++ b/src/tools/tidy/src/watcher.rs
@@ -0,0 +1,176 @@
+//! Checks that text between tags unchanged, emitting warning otherwise,
+//! allowing asserting that code in different places over codebase is in sync.
+//!
+//! This works via hashing text between tags and saving hash in tidy.
+//!
+//! Usage:
+//!
+//! some.rs:
+//! // tidy-ticket-foo
+//! const FOO: usize = 42;
+//! // tidy-ticket-foo
+//!
+//! some.sh:
+//! # tidy-ticket-foo
+//! export FOO=42
+//! # tidy-ticket-foo
+use std::fs;
+use std::fs::OpenOptions;
+use std::path::{Path, PathBuf};
+
+use md5::{Digest, Md5};
+use serde::{Deserialize, Serialize};
+use serde_json;
+
+#[cfg(test)]
+mod tests;
+
+#[derive(Deserialize, Serialize, Debug)]
+struct TagGroups {
+    tag_groups: Vec<TagGroup>,
+}
+
+#[derive(Deserialize, Serialize, Debug)]
+struct TagGroup {
+    name: String,
+    #[serde(skip_serializing_if = "is_false")]
+    #[serde(default)]
+    /// if group sync in broken but you don't want to remove it
+    is_off: bool,
+    tags: Vec<Tag>,
+}
+
+#[derive(Deserialize, Serialize, Debug)]
+struct Tag {
+    /// path to file
+    path: PathBuf,
+    /// md5 tag of tag content
+    hash: String,
+    /// tag string
+    tag: String,
+}
+
+fn is_false(b: &bool) -> bool {
+    !b
+}
+
+/// Return hash for source text between 2 tag occurrence,
+/// ignoring lines where tag written
+///
+/// Expecting:
+/// tag is not multiline
+/// source always have at least 2 occurrence of tag (>2 ignored)
+fn span_hash(source: &str, tag: &str, bad: &mut bool, file_path: &Path) -> Result<String, ()> {
+    let start_idx = match source.find(tag) {
+        Some(idx) => idx,
+        None => {
+            return Err(tidy_error!(
+                bad,
+                "tag {} should exist in file {}",
+                tag,
+                file_path.display()
+            ));
+        }
+    };
+    let end_idx = {
+        let end = match source[start_idx + tag.len()..].find(tag) {
+            // index from source start
+            Some(idx) => start_idx + tag.len() + idx,
+            None => return Err(tidy_error!(bad, "tag end {} should exist in provided text", tag)),
+        };
+        // second line with tag can contain some other text before tag, ignore it
+        // by finding position of previous line ending
+        //
+        // FIXME: what if line ending is \r\n? In that case \r will be hashed too
+        let offset = source[start_idx..end].rfind('\n').unwrap();
+        start_idx + offset
+    };
+
+    let mut hasher = Md5::new();
+
+    source[start_idx..end_idx]
+        .lines()
+        // skip first line with tag
+        .skip(1)
+        // hash next lines, ignoring end trailing whitespaces
+        .for_each(|line| {
+            let trimmed = line.trim_end();
+            hasher.update(trimmed);
+        });
+    Ok(format!("{:x}", hasher.finalize()))
+}
+
+fn check_entry(
+    entry: &mut Tag,
+    tag_group_name: &str,
+    bad: &mut bool,
+    root_path: &Path,
+    bless: bool,
+) {
+    let file_path = root_path.join(Path::new(&entry.path));
+    let file = fs::read_to_string(&file_path)
+        .unwrap_or_else(|e| panic!("{:?}, path: {}", e, entry.path.display()));
+    let actual_hash = span_hash(&file, &entry.tag, bad, &file_path).unwrap();
+    if actual_hash != entry.hash {
+        if !bless {
+            // Write tidy error description for watcher only once.
+            // Will not work if there was previous errors of other types.
+            if *bad == false {
+                tidy_error!(
+                    bad,
+                    "The code blocks tagged with tidy watcher has changed.\n\
+                 It's likely that code blocks with the following tags need to be changed too. Check src/tools/tidy/src/watcher.rs, find tag/hash in TIDY_WATCH_LIST list \
+                and verify that sources for provided group of tags in sync. Once that done, run tidy again and update hashes in TIDY_WATCH_LIST with provided actual hashes."
+                )
+            }
+            tidy_error!(
+                bad,
+                "hash for tag `{}` in path `{}` mismatch:\n  actual: `{}`, expected: `{}`\n  \
+            Verify that tags from tag_group `{}` in sync.",
+                entry.tag,
+                entry.path.display(),
+                actual_hash,
+                entry.hash,
+                tag_group_name,
+            );
+        } else {
+            entry.hash = actual_hash;
+        }
+    }
+}
+
+/*
+    // sync self-profile-events help mesage with actual list of events
+    add_group!(
+        ("compiler/rustc_data_structures/src/profiling.rs", "881e7899c7d6904af1bc000594ee0418", "tidy-ticket-self-profile-events"),
+        ("compiler/rustc_session/src/options.rs", "012ee5a3b61ee1377744e5c6913fa00a", "tidy-ticket-self-profile-events")
+    ),
+
+    // desynced, pieces in compiler/rustc_pattern_analysis/src/rustc.rs
+    // add_group!(
+    //     ("compiler/rustc_pattern_analysis/src/constructor.rs", "c17706947fc814aa5648972a5b3dc143", "tidy-ticket-arity"),
+    //     // ("compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs", "7ce77b84c142c22530b047703ef209f0", "tidy-ticket-wildcards")
+    // ),
+
+    // desynced, pieces in compiler/rustc_hir_analysis/src/lib.rs missing?
+    //add_group!( // bad
+    //    ("compiler/rustc_hir_analysis/src/lib.rs", "842e23fb65caf3a96681686131093316", "tidy-ticket-sess-time-item_types_checking"),
+    //    ("src/librustdoc/core.rs", "85d9dd0cbb94fd521e2d15a8ed38a75f", "tidy-ticket-sess-time-item_types_checking")
+    // ),
+*/
+pub fn check(root_path: &Path, bless: bool, bad: &mut bool) {
+    let config_path = root_path.join(Path::new("src/tools/tidy/src/watcher_list.json"));
+    let config_file = fs::read_to_string(&config_path).unwrap_or_else(|e| panic!("{:?}", e));
+    let mut tag_groups: TagGroups = serde_json::from_str(&config_file).unwrap();
+    for tag_group in tag_groups.tag_groups.iter_mut() {
+        if !tag_group.is_off {
+            for entry in tag_group.tags.iter_mut() {
+                check_entry(entry, &tag_group.name, bad, root_path, bless);
+            }
+        }
+    }
+    if bless {
+        let f = OpenOptions::new().write(true).truncate(true).open(config_path).unwrap();
+        serde_json::to_writer_pretty(f, &tag_groups).unwrap();
+    }
+}
diff --git a/src/tools/tidy/src/watcher/tests.rs b/src/tools/tidy/src/watcher/tests.rs
new file mode 100644
index 0000000000000..a097bc3944048
--- /dev/null
+++ b/src/tools/tidy/src/watcher/tests.rs
@@ -0,0 +1,51 @@
+use super::*;
+
+#[test]
+fn test_span_hash_one_line() {
+    let source = "some text\ntidy-tag\ncheckme=42\ntidy-tag\n";
+    let tag = "tidy-tag";
+    assert_eq!(
+        "42258eba764c3f94a24de379e5715dc8",
+        span_hash(source, tag, &mut true, Path::new("")).unwrap()
+    );
+}
+
+#[test]
+fn test_span_hash_multiple_lines() {
+    let source = "some text\ntidy-tag\ncheckme=42\nother line\ntidy-tag\n";
+    let tag = "tidy-tag";
+    assert_eq!(
+        "49cb23dc2032ceea671ca48092750a1c",
+        span_hash(source, tag, &mut true, Path::new("")).unwrap()
+    );
+}
+
+#[test]
+fn test_span_hash_has_some_text_in_line_with_tag() {
+    let source = "some text\ntidy-tag ignore me\ncheckme=42\nother line\ntidy-tag\n";
+    let tag = "tidy-tag";
+    assert_eq!(
+        "49cb23dc2032ceea671ca48092750a1c",
+        span_hash(source, tag, &mut true, Path::new("")).unwrap()
+    );
+}
+
+#[test]
+fn test_span_hash_has_some_text_in_line_before_second_tag() {
+    let source = r#"
+RUN ./build-clang.sh
+ENV CC=clang CXX=clang++
+# tidy-ticket-perf-commit
+# rustc-perf version from 2023-05-30
+ENV PERF_COMMIT 8b2ac3042e1ff2c0074455a0a3618adef97156b1
+# tidy-ticket-perf-commit
+RUN curl -LS -o perf.zip https://github.com/rust-lang/rustc-perf/archive/$PERF_COMMIT.zip && \
+    unzip perf.zip && \
+    mv rustc-perf-$PERF_COMMIT rustc-perf && \
+    rm perf.zip"#;
+    let tag = "tidy-ticket-perf-commit";
+    assert_eq!(
+        "76c8d9783e38e25a461355f82fcd7955",
+        span_hash(source, tag, &mut true, Path::new("")).unwrap()
+    );
+}
diff --git a/src/tools/tidy/src/watcher_list.json b/src/tools/tidy/src/watcher_list.json
new file mode 100644
index 0000000000000..cc958245b5fb6
--- /dev/null
+++ b/src/tools/tidy/src/watcher_list.json
@@ -0,0 +1,256 @@
+{
+  "tag_groups": [
+    {
+      "name": "group_1",
+      "tags": [
+        {
+          "path": "compiler/rustc_ast/src/token.rs",
+          "hash": "2df3e863dc4caffb31a7ddf001517232",
+          "tag": "tidy-ticket-ast-from_token"
+        },
+        {
+          "path": "compiler/rustc_ast/src/token.rs",
+          "hash": "3279df5da05e0455f45630917fe2a797",
+          "tag": "tidy-ticket-ast-can_begin_literal_maybe_minus"
+        },
+        {
+          "path": "compiler/rustc_parse/src/parser/expr.rs",
+          "hash": "479655a8587512fc26f7361d7bbd75a5",
+          "tag": "tidy-ticket-rustc_parse-can_begin_literal_maybe_minus"
+        }
+      ]
+    },
+    {
+      "name": "group_2",
+      "tags": [
+        {
+          "path": "compiler/rustc_builtin_macros/src/assert/context.rs",
+          "hash": "dbac73cc47a451d4822ccd3010c40a0f",
+          "tag": "tidy-ticket-all-expr-kinds"
+        },
+        {
+          "path": "tests/ui/macros/rfc-2011-nicer-assert-messages/all-expr-kinds.rs",
+          "hash": "78ce54cc25baeac3ae07c876db25180c",
+          "tag": "tidy-ticket-all-expr-kinds"
+        }
+      ]
+    },
+    {
+      "name": "group_3",
+      "tags": [
+        {
+          "path": "compiler/rustc_const_eval/src/interpret/validity.rs",
+          "hash": "c4e96ecd3f81dcb54541b8ea41042e8f",
+          "tag": "tidy-ticket-try_visit_primitive"
+        },
+        {
+          "path": "compiler/rustc_const_eval/src/interpret/validity.rs",
+          "hash": "cbe69005510c1a87ab07db601c0d36b8",
+          "tag": "tidy-ticket-visit_value"
+        }
+      ]
+    },
+    {
+      "name": "group_4",
+      "tags": [
+        {
+          "path": "compiler/rustc_data_structures/src/profiling.rs",
+          "hash": "881e7899c7d6904af1bc000594ee0418",
+          "tag": "tidy-ticket-self-profile-events"
+        },
+        {
+          "path": "compiler/rustc_session/src/options.rs",
+          "hash": "012ee5a3b61ee1377744e5c6913fa00a",
+          "tag": "tidy-ticket-self-profile-events"
+        }
+      ]
+    },
+    {
+      "name": "group_5",
+      "tags": [
+        {
+          "path": "compiler/rustc_errors/src/json.rs",
+          "hash": "3963a8c4eee7f87eeb076622b8a92891",
+          "tag": "tidy-ticket-UnusedExterns"
+        },
+        {
+          "path": "src/librustdoc/doctest.rs",
+          "hash": "14da85663568149c9b21686f4b7fa7b0",
+          "tag": "tidy-ticket-UnusedExterns"
+        }
+      ]
+    },
+    {
+      "name": "group_6",
+      "tags": [
+        {
+          "path": "compiler/rustc_middle/src/ty/util.rs",
+          "hash": "cae64b1bc854e7ee81894212facb5bfa",
+          "tag": "tidy-ticket-static_ptr_ty"
+        },
+        {
+          "path": "compiler/rustc_middle/src/ty/util.rs",
+          "hash": "6f5ead08474b4d3e358db5d3c7aef970",
+          "tag": "tidy-ticket-thread_local_ptr_ty"
+        }
+      ]
+    },
+    {
+      "name": "group_7",
+      "tags": [
+        {
+          "path": "compiler/rustc_monomorphize/src/partitioning.rs",
+          "hash": "f4f33e9c14f4e0c3a20b5240ae36a7c8",
+          "tag": "tidy-ticket-short_description"
+        },
+        {
+          "path": "compiler/rustc_codegen_ssa/src/back/write.rs",
+          "hash": "5286f7f76fcf564c98d7a8eaeec39b18",
+          "tag": "tidy-ticket-short_description"
+        }
+      ]
+    },
+    {
+      "name": "group_8",
+      "tags": [
+        {
+          "path": "compiler/rustc_session/src/config/sigpipe.rs",
+          "hash": "330e0776ba5a6c0a7439a5235297f08f",
+          "tag": "tidy-ticket-sigpipe"
+        },
+        {
+          "path": "library/std/src/sys/pal/unix/mod.rs",
+          "hash": "2cdc37081831cdcf44f3331efbe440af",
+          "tag": "tidy-ticket-sigpipe"
+        }
+      ]
+    },
+    {
+      "name": "group_9",
+      "tags": [
+        {
+          "path": "compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs",
+          "hash": "8726918d084e0ac5bb07184008403f88",
+          "tag": "tidy-ticket-extract_tupled_inputs_and_output_from_callable"
+        },
+        {
+          "path": "compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs",
+          "hash": "be2967d323633c7458533c6cec228273",
+          "tag": "tidy-ticket-assemble_fn_pointer_candidates"
+        }
+      ]
+    },
+    {
+      "name": "group_10",
+      "tags": [
+        {
+          "path": "compiler/rustc_trait_selection/src/traits/project.rs",
+          "hash": "262d10feb1b7ba8d3ffb4a95314bf404",
+          "tag": "tidy-ticket-assemble_candidates_from_impls-UserDefined"
+        },
+        {
+          "path": "compiler/rustc_ty_utils/src/instance.rs",
+          "hash": "a51a6022efb405c5ee86acdf49ec222d",
+          "tag": "tidy-ticket-resolve_associated_item-UserDefined"
+        }
+      ]
+    },
+    {
+      "name": "group_11",
+      "tags": [
+        {
+          "path": "library/core/src/ptr/metadata.rs",
+          "hash": "357c958a096c33bed67cfc7212d940a2",
+          "tag": "tidy-ticket-static_assert_expected_bounds_for_metadata"
+        },
+        {
+          "path": "library/core/tests/ptr.rs",
+          "hash": "d8c47e54b871d72dfdce56e6a89b5c31",
+          "tag": "tidy-ticket-static_assert_expected_bounds_for_metadata"
+        }
+      ]
+    },
+    {
+      "name": "group_12",
+      "is_off": true,
+      "tags": [
+        {
+          "path": "compiler/rustc_pattern_analysis/src/constructor.rs",
+          "hash": "c17706947fc814aa5648972a5b3dc143",
+          "tag": "tidy-ticket-arity"
+        },
+        {
+          "path": "compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs",
+          "hash": "7ce77b84c142c22530b047703ef209f0",
+          "tag": "tidy-ticket-wildcards"
+        }
+      ]
+    },
+    {
+      "name": "group_13",
+      "is_off": true,
+      "tags": [
+        {
+          "path": "compiler/rustc_hir_analysis/src/lib.rs",
+          "hash": "842e23fb65caf3a96681686131093316",
+          "tag": "tidy-ticket-sess-time-item_types_checking"
+        },
+        {
+          "path": "src/librustdoc/core.rs",
+          "hash": "85d9dd0cbb94fd521e2d15a8ed38a75f",
+          "tag": "tidy-ticket-sess-time-item_types_checking"
+        }
+      ]
+    },
+    {
+      "name": "group_14",
+      "tags": [
+        {
+          "path": "library/core/src/panicking.rs",
+          "hash": "b5387987dd6c927acf5ddfa33fdf3090",
+          "tag": "tidy-ticket-panic-message-nounwind"
+        },
+        {
+          "path": "library/core/src/panicking.rs",
+          "hash": "f07f9a5af83a08e7287cd81226be8834",
+          "tag": "tidy-ticket-panic-message-nobacktrace"
+        },
+        {
+          "path": "compiler/rustc_middle/src/mir/terminator.rs",
+          "hash": "110baa63da1da4d6ae54938b4bbd070f",
+          "tag": "tidy-ticket-panic-message"
+        }
+      ]
+    },
+    {
+      "name": "group_15",
+      "tags": [
+        {
+          "path": "compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs",
+          "hash": "50a549340456169ab3119d1dfecb6f96",
+          "tag": "tidy-ticket-evaluate_host_effect_for_destruct_goal"
+        },
+        {
+          "path": "compiler/rustc_trait_selection/src/traits/effects.rs",
+          "hash": "a280510e2a7424dd874f14ad2180a938",
+          "tag": "tidy-ticket-evaluate_host_effect_for_destruct_goal"
+        }
+      ]
+    },
+    {
+      "name": "group_16",
+      "tags": [
+        {
+          "path": "compiler/rustc_metadata/src/native_libs.rs",
+          "hash": "332941877827af57790ac82c2a40177f",
+          "tag": "tidy-ticket-copy_third_party_objects"
+        },
+        {
+          "path": "src/bootstrap/src/core/build_steps/compile.rs",
+          "hash": "ea843d88787238a509fdc5cb4ad3915b",
+          "tag": "tidy-ticket-copy_third_party_objects"
+        }
+      ]
+    }
+  ]
+}
\ No newline at end of file
diff --git a/tests/ui/macros/rfc-2011-nicer-assert-messages/all-expr-kinds.rs b/tests/ui/macros/rfc-2011-nicer-assert-messages/all-expr-kinds.rs
index de7dbb9052edb..268db0bfef906 100644
--- a/tests/ui/macros/rfc-2011-nicer-assert-messages/all-expr-kinds.rs
+++ b/tests/ui/macros/rfc-2011-nicer-assert-messages/all-expr-kinds.rs
@@ -7,6 +7,7 @@
 #![allow(path_statements, unused_allocation)]
 #![feature(core_intrinsics, generic_assert)]
 
+// tidy-keep-sync-with=tidy-ticket-all-expr-kinds
 macro_rules! test {
   (
     let mut $elem_ident:ident = $elem_expr:expr;
@@ -118,3 +119,4 @@ fn main() {
     [ -elem == -3 ] => "Assertion failed: -elem == -3\nWith captures:\n  elem = 1\n"
   );
 }
+// tidy-keep-sync-with=tidy-ticket-all-expr-kinds