Auto merge of #138499 - lcnr:borrowck-typeck_root, r=oli-obk

borrowck typeck children together with their root

This introduces new cycle errors, even with `feature(inline_const_pat)` removed, see the `non-structural-match-types-cycle-err.rs` test.

The new cycle error happens as the layout of `async`-blocks relies on their `optimized_mir`. As that now depends on `mir_borrowck` of its typeck parent, computing the layout of an `async`-block during MIR building, e.g. when evaluating a named `const` pattern. I think there's currently no way to have a named const pattern whose type references an async block while being allowed? cc `@oli-obk` `@RalfJung`

I cannot think of other cases where we currently rely on the MIR of a typeck children while borrowchecking their parent. The crater run came back without any breakage. My work here will prevent any future features which rely on this as we'll get locked into borrowchecking them together as I continue to work on https://github.com/rust-lang/types-team/issues/129, cc `@rust-lang/types.`

r? compiler-errors

4 files changed, 92 insertions, 26 deletions

diff --git a/tests/ui/pattern/non-structural-match-types-cycle-err.rs b/tests/ui/pattern/non-structural-match-types-cycle-err.rs
new file mode 100644
index 00000000000..a8e494c35b0
--- /dev/null
+++ b/tests/ui/pattern/non-structural-match-types-cycle-err.rs
@@ -0,0 +1,24 @@
+//@ edition:2021
+
+struct AnyOption<T>(T);
+impl<T> AnyOption<T> {
+    const NONE: Option<T> = None;
+}
+
+// This is an unfortunate side-effect of borrowchecking nested items
+// together with their parent. Evaluating the `AnyOption::<_>::NONE`
+// pattern for exhaustiveness checking relies on the layout of the
+// async block. This layout relies on `optimized_mir` of the nested
+// item which is now borrowck'd together with its parent. As
+// borrowck of the parent requires us to have already lowered the match,
+// this is a query cycle.
+
+fn uwu() {}
+fn defines() {
+    match Some(async {}) {
+        AnyOption::<_>::NONE => {}
+        //~^ ERROR cycle detected when building THIR for `defines`
+        _ => {}
+    }
+}
+fn main() {}
diff --git a/tests/ui/pattern/non-structural-match-types-cycle-err.stderr b/tests/ui/pattern/non-structural-match-types-cycle-err.stderr
new file mode 100644
index 00000000000..2f4ac63fc57
--- /dev/null
+++ b/tests/ui/pattern/non-structural-match-types-cycle-err.stderr
@@ -0,0 +1,64 @@
+error[E0391]: cycle detected when building THIR for `defines`
+  --> $DIR/non-structural-match-types-cycle-err.rs:19:9
+   |
+LL |         AnyOption::<_>::NONE => {}
+   |         ^^^^^^^^^^^^^^^^^^^^
+   |
+note: ...which requires evaluating type-level constant...
+  --> $DIR/non-structural-match-types-cycle-err.rs:5:5
+   |
+LL |     const NONE: Option<T> = None;
+   |     ^^^^^^^^^^^^^^^^^^^^^
+note: ...which requires const-evaluating + checking `<impl at $DIR/non-structural-match-types-cycle-err.rs:4:1: 4:21>::NONE`...
+  --> $DIR/non-structural-match-types-cycle-err.rs:5:5
+   |
+LL |     const NONE: Option<T> = None;
+   |     ^^^^^^^^^^^^^^^^^^^^^
+   = note: ...which requires computing layout of `core::option::Option<{async block@$DIR/non-structural-match-types-cycle-err.rs:18:16: 18:21}>`...
+   = note: ...which requires computing layout of `{async block@$DIR/non-structural-match-types-cycle-err.rs:18:16: 18:21}`...
+note: ...which requires optimizing MIR for `defines::{closure#0}`...
+  --> $DIR/non-structural-match-types-cycle-err.rs:18:16
+   |
+LL |     match Some(async {}) {
+   |                ^^^^^
+note: ...which requires elaborating drops for `defines::{closure#0}`...
+  --> $DIR/non-structural-match-types-cycle-err.rs:18:16
+   |
+LL |     match Some(async {}) {
+   |                ^^^^^
+note: ...which requires borrow-checking `defines`...
+  --> $DIR/non-structural-match-types-cycle-err.rs:17:1
+   |
+LL | fn defines() {
+   | ^^^^^^^^^^^^
+note: ...which requires promoting constants in MIR for `defines`...
+  --> $DIR/non-structural-match-types-cycle-err.rs:17:1
+   |
+LL | fn defines() {
+   | ^^^^^^^^^^^^
+note: ...which requires checking if `defines` contains FFI-unwind calls...
+  --> $DIR/non-structural-match-types-cycle-err.rs:17:1
+   |
+LL | fn defines() {
+   | ^^^^^^^^^^^^
+note: ...which requires building MIR for `defines`...
+  --> $DIR/non-structural-match-types-cycle-err.rs:17:1
+   |
+LL | fn defines() {
+   | ^^^^^^^^^^^^
+note: ...which requires match-checking `defines`...
+  --> $DIR/non-structural-match-types-cycle-err.rs:17:1
+   |
+LL | fn defines() {
+   | ^^^^^^^^^^^^
+   = note: ...which again requires building THIR for `defines`, completing the cycle
+note: cycle used when unsafety-checking `defines`
+  --> $DIR/non-structural-match-types-cycle-err.rs:17:1
+   |
+LL | fn defines() {
+   | ^^^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0391`.
diff --git a/tests/ui/pattern/non-structural-match-types.rs b/tests/ui/pattern/non-structural-match-types.rs
index 5869767c936..a5ff7fcdb5e 100644
--- a/tests/ui/pattern/non-structural-match-types.rs
+++ b/tests/ui/pattern/non-structural-match-types.rs
@@ -1,6 +1,4 @@
 //@ edition:2021
-#![feature(const_async_blocks)]
-
 struct AnyOption<T>(T);
 impl<T> AnyOption<T> {
     const NONE: Option<T> = None;
@@ -19,11 +17,5 @@ fn defines() {
         //~^ ERROR constant of non-structural type
         _ => {}
     }
-
-    match Some(async {}) {
-        AnyOption::<_>::NONE => {}
-        //~^ ERROR constant of non-structural type
-        _ => {}
-    }
 }
 fn main() {}
diff --git a/tests/ui/pattern/non-structural-match-types.stderr b/tests/ui/pattern/non-structural-match-types.stderr
index da675a9f3ff..3b74ffe7cb7 100644
--- a/tests/ui/pattern/non-structural-match-types.stderr
+++ b/tests/ui/pattern/non-structural-match-types.stderr
@@ -1,5 +1,5 @@
 error: constant of non-structural type `Option<fn() {uwu}>` in a pattern
-  --> $DIR/non-structural-match-types.rs:12:9
+  --> $DIR/non-structural-match-types.rs:10:9
    |
 LL | impl<T> AnyOption<T> {
    | --------------------
@@ -11,8 +11,8 @@ LL |         AnyOption::<_>::NONE => {}
    |
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
 
-error: constant of non-structural type `Option<{closure@$DIR/non-structural-match-types.rs:17:16: 17:18}>` in a pattern
-  --> $DIR/non-structural-match-types.rs:18:9
+error: constant of non-structural type `Option<{closure@$DIR/non-structural-match-types.rs:15:16: 15:18}>` in a pattern
+  --> $DIR/non-structural-match-types.rs:16:9
    |
 LL | impl<T> AnyOption<T> {
    | --------------------
@@ -24,19 +24,5 @@ LL |         AnyOption::<_>::NONE => {}
    |
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
 
-error: constant of non-structural type `Option<{async block@$DIR/non-structural-match-types.rs:23:16: 23:21}>` in a pattern
-  --> $DIR/non-structural-match-types.rs:24:9
-   |
-LL | impl<T> AnyOption<T> {
-   | --------------------
-LL |     const NONE: Option<T> = None;
-   |     --------------------- constant defined here
-...
-LL |         AnyOption::<_>::NONE => {}
-   |         ^^^^^^^^^^^^^^^^^^^^ constant of non-structural type
-   |
-   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
-   = note: `ResumeTy` must be annotated with `#[derive(PartialEq)]` to be usable in patterns
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors