Recover and ignore query cycles for unused_generic_params

Author: Noratrieb

compiler/rustc_macros/src/query.rs

@@ -97,6 +97,9 @@ struct QueryModifiers {
     /// A cycle error results in a delay_bug call
     cycle_delay_bug: Option<Ident>,
 
+    /// A cycle error will not be reported.
+    recover_cycle: Option<Ident>,
+
     /// Don't hash the result, instead just mark a query red if it runs
     no_hash: Option<Ident>,
 
@@ -125,6 +128,7 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
     let mut desc = None;
     let mut fatal_cycle = None;
     let mut cycle_delay_bug = None;
+    let mut recover_cycle = None;
     let mut no_hash = None;
     let mut anon = None;
     let mut eval_always = None;
@@ -179,6 +183,8 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
             try_insert!(fatal_cycle = modifier);
         } else if modifier == "cycle_delay_bug" {
             try_insert!(cycle_delay_bug = modifier);
+        } else if modifier == "recover_cycle" {
+            try_insert!(recover_cycle = modifier);
         } else if modifier == "no_hash" {
             try_insert!(no_hash = modifier);
         } else if modifier == "anon" {
@@ -206,6 +212,7 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
         desc,
         fatal_cycle,
         cycle_delay_bug,
+        recover_cycle,
         no_hash,
         anon,
         eval_always,
@@ -327,6 +334,7 @@ pub fn rustc_queries(input: TokenStream) -> TokenStream {
             fatal_cycle,
             arena_cache,
             cycle_delay_bug,
+            recover_cycle,
             no_hash,
             anon,
             eval_always,

compiler/rustc_middle/src/query/mod.rs

@@ -1846,6 +1846,7 @@ rustc_queries! {
                 tcx.def_path_str(key.def_id())
         }
         separate_provide_extern
+        recover_cycle
     }
 
     query backend_optimization_level(_: ()) -> OptLevel {

compiler/rustc_query_impl/src/plumbing.rs

@@ -205,6 +205,9 @@ macro_rules! handle_cycle_error {
     ([]) => {{
         rustc_query_system::HandleCycleError::Error
     }};
+    ([(recover_cycle) $($rest:tt)*]) => {{
+        rustc_query_system::HandleCycleError::Recover
+    }};
     ([(fatal_cycle) $($rest:tt)*]) => {{
         rustc_query_system::HandleCycleError::Fatal
     }};

compiler/rustc_query_system/src/error.rs

@@ -12,6 +12,7 @@ pub struct CycleStack {
 
 #[derive(Copy, Clone)]
 pub enum HandleCycleError {
+    Recover,
     Error,
     Fatal,
     DelayBug,

compiler/rustc_query_system/src/query/plumbing.rs

@@ -162,6 +162,11 @@ where
             error.delay_as_bug();
             Value::from_cycle_error(tcx, &cycle_error.cycle)
         }
+        Recover => {
+            // FIXME: We don't really want to create the error in the first place.
+            error.cancel();
+            Value::from_cycle_error(tcx, &cycle_error.cycle)
+        }
     }
 }