From ce04c6acbdae34e027656a4fbe72420dcc3d523f Mon Sep 17 00:00:00 2001
From: Matthew Jasper <mjjasper1@gmail.com>
Date: Thu, 18 May 2023 19:03:34 +0100
Subject: [PATCH] Propagate recursion depth in collect_predicates_for_types

---
 .../src/traits/select/mod.rs                  |  3 +-
 tests/ui/traits/cycle-cache-err-60010.stderr  | 18 ++++-
 tests/ui/traits/cycle-recursion-limit.rs      | 74 +++++++++++++++++++
 tests/ui/traits/cycle-recursion-limit.stderr  | 25 +++++++
 4 files changed, 118 insertions(+), 2 deletions(-)
 create mode 100644 tests/ui/traits/cycle-recursion-limit.rs
 create mode 100644 tests/ui/traits/cycle-recursion-limit.stderr

diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index b72ff5b78e418..4bbb5ba55b77f 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2409,9 +2409,10 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                         )
                     });
 
-                let obligation = Obligation::new(
+                let obligation = Obligation::with_depth(
                     self.tcx(),
                     cause.clone(),
+                    recursion_depth,
                     param_env,
                     ty::TraitRef::new(self.tcx(), trait_def_id, [normalized_ty]),
                 );
diff --git a/tests/ui/traits/cycle-cache-err-60010.stderr b/tests/ui/traits/cycle-cache-err-60010.stderr
index 2ff16b4af38d4..aee41c43aefeb 100644
--- a/tests/ui/traits/cycle-cache-err-60010.stderr
+++ b/tests/ui/traits/cycle-cache-err-60010.stderr
@@ -1,9 +1,25 @@
-error[E0275]: overflow evaluating the requirement `RootDatabase: RefUnwindSafe`
+error[E0275]: overflow evaluating the requirement `SalsaStorage: RefUnwindSafe`
   --> $DIR/cycle-cache-err-60010.rs:27:13
    |
 LL |     _parse: <ParseQuery as Query<RootDatabase>>::Data,
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+note: required because it appears within the type `PhantomData<SalsaStorage>`
+  --> $SRC_DIR/core/src/marker.rs:LL:COL
+note: required because it appears within the type `Unique<SalsaStorage>`
+  --> $SRC_DIR/core/src/ptr/unique.rs:LL:COL
+note: required because it appears within the type `Box<SalsaStorage>`
+  --> $SRC_DIR/alloc/src/boxed.rs:LL:COL
+note: required because it appears within the type `Runtime<RootDatabase>`
+  --> $DIR/cycle-cache-err-60010.rs:23:8
+   |
+LL | struct Runtime<DB: Database> {
+   |        ^^^^^^^
+note: required because it appears within the type `RootDatabase`
+  --> $DIR/cycle-cache-err-60010.rs:20:8
+   |
+LL | struct RootDatabase {
+   |        ^^^^^^^^^^^^
 note: required for `RootDatabase` to implement `SourceDatabase`
   --> $DIR/cycle-cache-err-60010.rs:44:9
    |
diff --git a/tests/ui/traits/cycle-recursion-limit.rs b/tests/ui/traits/cycle-recursion-limit.rs
new file mode 100644
index 0000000000000..1890251ba7197
--- /dev/null
+++ b/tests/ui/traits/cycle-recursion-limit.rs
@@ -0,0 +1,74 @@
+//~ ERROR overflow
+// Test that we properly detect the cycle amongst the traits
+// here and report an error.
+
+use std::panic::RefUnwindSafe;
+
+trait Database {
+    type Storage;
+}
+trait HasQueryGroup {}
+trait Query<DB> {
+    type Data;
+}
+trait SourceDatabase {
+    fn parse(&self) {
+        loop {}
+    }
+}
+
+struct ParseQuery;
+struct RootDatabase {
+    _runtime: Runtime<RootDatabase>,
+}
+struct Runtime<DB: Database> {
+    _storage: Box<DB::Storage>,
+}
+struct SalsaStorage {
+    _parse: <ParseQuery as Query<RootDatabase>>::Data,
+}
+
+impl Database for RootDatabase {
+    // This would also be an error if we didn't abort compilation on the error
+    // above.
+    type Storage = SalsaStorage;
+}
+impl HasQueryGroup for RootDatabase {}
+impl<DB> Query<DB> for ParseQuery
+where
+    DB: SourceDatabase,
+    DB: Database,
+{
+    type Data = RootDatabase;
+}
+impl<T> Database for T
+where
+    T: RefUnwindSafe,
+    T: HasQueryGroup,
+{
+}
+
+pub(crate) fn goto_implementation(db: &RootDatabase) -> u32 {
+    // This is not satisfied:
+    //
+    // - `RootDatabase: SourceDatabase`
+    //   - requires `RootDatabase: RefUnwindSafe` + `RootDatabase: HasQueryGroup`
+    // - `RootDatabase: RefUnwindSafe`
+    //   - requires `Runtime<RootDatabase>: RefUnwindSafe`
+    // - `Runtime<RootDatabase>: RefUnwindSafe`
+    //   - requires `DB::Storage: RefUnwindSafe` (`SalsaStorage: RefUnwindSafe`)
+    // - `SalsaStorage: RefUnwindSafe`
+    //    - requires `<ParseQuery as Query<RootDatabase>>::Data: RefUnwindSafe`,
+    //      which means `ParseQuery: Query<RootDatabase>`
+    // - `ParseQuery: Query<RootDatabase>`
+    //    - requires `RootDatabase: SourceDatabase`,
+    // - `RootDatabase: SourceDatabase` is already on the stack, so we have a
+    //   cycle with non-coinductive participants
+    //
+    // we used to fail to report an error here because we got the
+    // caching wrong.
+    SourceDatabase::parse(db);
+    22
+}
+
+fn main() {}
diff --git a/tests/ui/traits/cycle-recursion-limit.stderr b/tests/ui/traits/cycle-recursion-limit.stderr
new file mode 100644
index 0000000000000..ca1bad428be70
--- /dev/null
+++ b/tests/ui/traits/cycle-recursion-limit.stderr
@@ -0,0 +1,25 @@
+error[E0275]: overflow evaluating the requirement `Runtime<RootDatabase>: RefUnwindSafe`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`cycle_recursion_limit`)
+note: required because it appears within the type `RootDatabase`
+  --> $DIR/cycle-recursion-limit.rs:21:8
+   |
+LL | struct RootDatabase {
+   |        ^^^^^^^^^^^^
+note: required for `RootDatabase` to implement `Database`
+  --> $DIR/cycle-recursion-limit.rs:44:9
+   |
+LL | impl<T> Database for T
+   |         ^^^^^^^^     ^
+LL | where
+LL |     T: RefUnwindSafe,
+   |        ------------- unsatisfied trait bound introduced here
+note: required because it appears within the type `Runtime<RootDatabase>`
+  --> $DIR/cycle-recursion-limit.rs:24:8
+   |
+LL | struct Runtime<DB: Database> {
+   |        ^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0275`.