Don't cause a cycle when formatting query description that references a FnDef

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -675,8 +675,12 @@ fn pretty_print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error>
                 p!(")")
             }
             ty::FnDef(def_id, substs) => {
-                let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
+                if NO_QUERIES.with(|q| q.get()) {
-                p!(print(sig), " {{", print_value_path(def_id, substs), "}}");
+                    p!(print_def_path(def_id, substs));
+                } else {
+                    let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
+                    p!(print(sig), " {{", print_value_path(def_id, substs), "}}");
+                }
             }
             ty::FnPtr(ref bare_fn) => p!(print(bare_fn)),
             ty::Infer(infer_ty) => {
@@ -732,13 +736,13 @@ fn pretty_print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error>
             }
             ty::Placeholder(placeholder) => p!(write("Placeholder({:?})", placeholder)),
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                // FIXME(eddyb) print this with `print_def_path`.
                 // We use verbose printing in 'NO_QUERIES' mode, to
                 // avoid needing to call `predicates_of`. This should
                 // only affect certain debug messages (e.g. messages printed
                 // from `rustc_middle::ty` during the computation of `tcx.predicates_of`),
                 // and should have no effect on any compiler output.
-                if self.should_print_verbose() || NO_QUERIES.with(|q| q.get()) {
+                if self.should_print_verbose() {
+                    // FIXME(eddyb) print this with `print_def_path`.
                     p!(write("Opaque({:?}, {:?})", def_id, substs));
                     return Ok(self);
                 }
@@ -746,6 +750,8 @@ fn pretty_print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error>
                 let parent = self.tcx().parent(def_id);
                 match self.tcx().def_kind(parent) {
                     DefKind::TyAlias | DefKind::AssocTy => {
+                        // NOTE: I know we should check for NO_QUERIES here, but it's alright.
+                        // `type_of` on a TAIT should never cause a cycle.
                         if let ty::Alias(ty::Opaque, ty::AliasTy { def_id: d, .. }) =
                             *self.tcx().type_of(parent).kind()
                         {
@@ -760,7 +766,14 @@ fn pretty_print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error>
                         p!(print_def_path(def_id, substs));
                         return Ok(self);
                     }
-                    _ => return self.pretty_print_opaque_impl_type(def_id, substs),
+                    _ => {
+                        if NO_QUERIES.with(|q| q.get()) {
+                            p!(print_def_path(def_id, &[]));
+                            return Ok(self);
+                        } else {
+                            return self.pretty_print_opaque_impl_type(def_id, substs);
+                        }
+                    }
                 }
             }
             ty::Str => p!("str"),

compiler/rustc_query_impl/src/plumbing.rs

@@ -314,11 +314,14 @@ pub(crate) fn create_query_frame<
     kind: DepKind,
     name: &'static str,
 ) -> QueryStackFrame<DepKind> {
-    // Disable visible paths printing for performance reasons.
+    // Avoid calling queries while formatting the description
-    // Showing visible path instead of any path is not that important in production.
+    let description = ty::print::with_no_queries!(
-    let description = ty::print::with_no_visible_paths!(
+        // Disable visible paths printing for performance reasons.
-        // Force filename-line mode to avoid invoking `type_of` query.
+        // Showing visible path instead of any path is not that important in production.
-        ty::print::with_forced_impl_filename_line!(do_describe(tcx.tcx, key))
+        ty::print::with_no_visible_paths!(
+            // Force filename-line mode to avoid invoking `type_of` query.
+            ty::print::with_forced_impl_filename_line!(do_describe(tcx.tcx, key))
+        )
     );
     let description =
         if tcx.sess.verbose() { format!("{description} [{name:?}]") } else { description };

tests/ui/async-await/no-const-async.stderr

@@ -28,8 +28,8 @@ note: ...which requires const checking `x`...
    |
 LL | pub const async fn x() {}
    | ^^^^^^^^^^^^^^^^^^^^^^
-   = note: ...which requires computing whether `impl core::future::future::Future<Output = ()>` is freeze...
+   = note: ...which requires computing whether `x::{opaque#0}` is freeze...
-   = note: ...which requires evaluating trait selection obligation `impl core::future::future::Future<Output = ()>: core::marker::Freeze`...
+   = note: ...which requires evaluating trait selection obligation `x::{opaque#0}: core::marker::Freeze`...
    = note: ...which again requires computing type of `x::{opaque#0}`, completing the cycle
 note: cycle used when checking item types in top-level module
   --> $DIR/no-const-async.rs:4:1

tests/ui/impl-trait/auto-trait-leak.stderr

@@ -39,7 +39,7 @@ note: ...which requires type-checking `cycle1`...
    |
 LL |     send(cycle2().clone());
    |     ^^^^
-   = note: ...which requires evaluating trait selection obligation `impl core::clone::Clone: core::marker::Send`...
+   = note: ...which requires evaluating trait selection obligation `cycle2::{opaque#0}: core::marker::Send`...
 note: ...which requires computing type of `cycle2::{opaque#0}`...
   --> $DIR/auto-trait-leak.rs:19:16
    |
@@ -80,7 +80,7 @@ note: ...which requires type-checking `cycle2`...
    |
 LL |     send(cycle1().clone());
    |     ^^^^
-   = note: ...which requires evaluating trait selection obligation `impl core::clone::Clone: core::marker::Send`...
+   = note: ...which requires evaluating trait selection obligation `cycle1::{opaque#0}: core::marker::Send`...
    = note: ...which again requires computing type of `cycle1::{opaque#0}`, completing the cycle
 note: cycle used when checking item types in top-level module
   --> $DIR/auto-trait-leak.rs:1:1

tests/ui/parser/fn-header-semantic-fail.stderr

@@ -209,8 +209,8 @@ note: ...which requires const checking `main::ff5`...
    |
 LL |     const async unsafe extern "C" fn ff5() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: ...which requires computing whether `impl core::future::future::Future<Output = ()>` is freeze...
+   = note: ...which requires computing whether `main::ff5::{opaque#0}` is freeze...
-   = note: ...which requires evaluating trait selection obligation `impl core::future::future::Future<Output = ()>: core::marker::Freeze`...
+   = note: ...which requires evaluating trait selection obligation `main::ff5::{opaque#0}: core::marker::Freeze`...
    = note: ...which again requires computing type of `main::ff5::{opaque#0}`, completing the cycle
 note: cycle used when checking item types in top-level module
   --> $DIR/fn-header-semantic-fail.rs:5:1
@@ -245,8 +245,8 @@ note: ...which requires const checking `main::<impl at $DIR/fn-header-semantic-f
    |
 LL |         const async unsafe extern "C" fn ft5() {}
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: ...which requires computing whether `impl core::future::future::Future<Output = ()>` is freeze...
+   = note: ...which requires computing whether `main::<impl at $DIR/fn-header-semantic-fail.rs:28:5: 28:17>::ft5::{opaque#0}` is freeze...
-   = note: ...which requires evaluating trait selection obligation `impl core::future::future::Future<Output = ()>: core::marker::Freeze`...
+   = note: ...which requires evaluating trait selection obligation `main::<impl at $DIR/fn-header-semantic-fail.rs:28:5: 28:17>::ft5::{opaque#0}: core::marker::Freeze`...
    = note: ...which again requires computing type of `main::<impl at $DIR/fn-header-semantic-fail.rs:28:5: 28:17>::ft5::{opaque#0}`, completing the cycle
 note: cycle used when checking item types in top-level module
   --> $DIR/fn-header-semantic-fail.rs:5:1
@@ -281,8 +281,8 @@ note: ...which requires const checking `main::<impl at $DIR/fn-header-semantic-f
    |
 LL |         const async unsafe extern "C" fn fi5() {}
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: ...which requires computing whether `impl core::future::future::Future<Output = ()>` is freeze...
+   = note: ...which requires computing whether `main::<impl at $DIR/fn-header-semantic-fail.rs:40:5: 40:11>::fi5::{opaque#0}` is freeze...
-   = note: ...which requires evaluating trait selection obligation `impl core::future::future::Future<Output = ()>: core::marker::Freeze`...
+   = note: ...which requires evaluating trait selection obligation `main::<impl at $DIR/fn-header-semantic-fail.rs:40:5: 40:11>::fi5::{opaque#0}: core::marker::Freeze`...
    = note: ...which again requires computing type of `main::<impl at $DIR/fn-header-semantic-fail.rs:40:5: 40:11>::fi5::{opaque#0}`, completing the cycle
 note: cycle used when checking item types in top-level module
   --> $DIR/fn-header-semantic-fail.rs:5:1

tests/ui/query-system/no-query-in-printing-during-query-descr.rs

@@ -0,0 +1,6 @@
+fn a() -> _ {
+    //~^ ERROR the placeholder `_` is not allowed within types on item signatures for return types
+    &a
+}
+
+fn main() {}

tests/ui/query-system/no-query-in-printing-during-query-descr.stderr

@@ -0,0 +1,9 @@
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
+  --> $DIR/no-query-in-printing-during-query-descr.rs:1:11
+   |
+LL | fn a() -> _ {
+   |           ^ not allowed in type signatures
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0121`.