From db5ed4bd799cda1217ec6431ffa56cecd09ef6e9 Mon Sep 17 00:00:00 2001
From: Michael Baikov <manpacket@gmail.com>
Date: Thu, 13 Jun 2024 08:27:21 -0400
Subject: [PATCH] Allow for try_force_from_dep_node to fail

The way it is implemented currently try_force_from_dep_node returns true
as long as there's a function to force the query. It wasn't this way
from the beginning, earlier version was producing forcing result and it
was changed in https://github.com/rust-lang/rust/pull/89978, I couldn't
find any comments addressing this change.

One way it can fail is by failing to recover the query in
DepNodeParams::recover - when we are trying to query something that no
longer exists in the current environment
---
 .../rustc_query_system/src/dep_graph/mod.rs   | 18 +++++----
 tests/incremental/unrecoverable_query.rs      | 40 +++++++++++++++++++
 2 files changed, 51 insertions(+), 7 deletions(-)
 create mode 100644 tests/incremental/unrecoverable_query.rs

diff --git a/compiler/rustc_query_system/src/dep_graph/mod.rs b/compiler/rustc_query_system/src/dep_graph/mod.rs
index cbd80295887..cfb25ec905f 100644
--- a/compiler/rustc_query_system/src/dep_graph/mod.rs
+++ b/compiler/rustc_query_system/src/dep_graph/mod.rs
@@ -51,20 +51,24 @@ fn is_eval_always(self, kind: DepKind) -> bool {
     }
 
     /// Try to force a dep node to execute and see if it's green.
+    ///
+    /// Returns true if the query has actually been forced. It is valid that a query
+    /// fails to be forced, e.g. when the query key cannot be reconstructed from the
+    /// dep-node or when the query kind outright does not support it.
     #[inline]
     #[instrument(skip(self, frame), level = "debug")]
     fn try_force_from_dep_node(self, dep_node: DepNode, frame: Option<&MarkFrame<'_>>) -> bool {
         let cb = self.dep_kind_info(dep_node.kind);
         if let Some(f) = cb.force_from_dep_node {
-            if let Err(value) = panic::catch_unwind(panic::AssertUnwindSafe(|| {
-                f(self, dep_node);
-            })) {
-                if !value.is::<rustc_errors::FatalErrorMarker>() {
-                    print_markframe_trace(self.dep_graph(), frame);
+            match panic::catch_unwind(panic::AssertUnwindSafe(|| f(self, dep_node))) {
+                Err(value) => {
+                    if !value.is::<rustc_errors::FatalErrorMarker>() {
+                        print_markframe_trace(self.dep_graph(), frame);
+                    }
+                    panic::resume_unwind(value)
                 }
-                panic::resume_unwind(value)
+                Ok(query_has_been_forced) => query_has_been_forced,
             }
-            true
         } else {
             false
         }
diff --git a/tests/incremental/unrecoverable_query.rs b/tests/incremental/unrecoverable_query.rs
new file mode 100644
index 00000000000..e17236bebd2
--- /dev/null
+++ b/tests/incremental/unrecoverable_query.rs
@@ -0,0 +1,40 @@
+// If it is impossible to find query arguments just from the hash
+// compiler should treat the node as red
+
+// In this test prior to fixing compiler was having problems figuring out
+// drop impl for T inside of m
+
+//@ revisions:cfail1 cfail2
+//@ compile-flags: --crate-type=lib
+//@ build-pass
+
+pub trait P {
+    type A;
+}
+
+struct S;
+
+impl P for S {
+    type A = C;
+}
+
+struct T<D: P>(D::A, Z<D>);
+
+struct Z<D: P>(D::A, String);
+
+impl<D: P> T<D> {
+    pub fn i() -> Self {
+        loop {}
+    }
+}
+
+enum C {
+    #[cfg(cfail1)]
+    Up(()),
+    #[cfg(cfail2)]
+    Lorry(()),
+}
+
+pub fn m() {
+    T::<S>::i();
+}