Point out source of recursion

compiler-errors · compiler-errors · commit 389aee68b632 · 2023-11-08T07:27:40.000Z
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
@@ -1531,7 +1531,10 @@ pub enum CoroutineKind {
 
 impl CoroutineKind {
     pub fn is_fn_like(self) -> bool {
-        matches!(self, CoroutineKind::Async(CoroutineSource::Fn) | CoroutineKind::Gen(CoroutineSource::Fn))
+        matches!(
+            self,
+            CoroutineKind::Async(CoroutineSource::Fn) | CoroutineKind::Gen(CoroutineSource::Fn)
+        )
     }
 }
 
diff --git a/compiler/rustc_middle/src/values.rs b/compiler/rustc_middle/src/values.rs
@@ -136,9 +136,9 @@ impl<'tcx, T> Value<TyCtxt<'tcx>> for Result<T, &'_ ty::layout::LayoutError<'_>>
         _guar: ErrorGuaranteed,
     ) -> Self {
         let guar = if cycle_error.cycle[0].query.dep_kind == dep_kinds::layout_of
-            && let Some(def_id) = cycle_error.cycle[0].query.ty_def_id
-            && let Some(def_id) = def_id.as_local()
-            && matches!(tcx.def_kind(def_id), DefKind::Coroutine)
+              && let Some(def_id) = cycle_error.cycle[0].query.ty_def_id
+              && let Some(def_id) = def_id.as_local()
+              && matches!(tcx.def_kind(def_id), DefKind::Coroutine)
         {
             let hir = tcx.hir();
             let coroutine_kind = hir
@@ -154,13 +154,37 @@ impl<'tcx, T> Value<TyCtxt<'tcx>> for Result<T, &'_ ty::layout::LayoutError<'_>>
             } else {
                 tcx.def_span(def_id)
             };
-            struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing")
-                .span_label(span, "recursive `async fn`")
-                .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
-                .note(
-                    "consider using the `async_recursion` crate: https://crates.io/crates/async_recursion",
-                )
-                .emit()
+            let mut diag = struct_span_err!(
+                tcx.sess,
+                span,
+                E0733,
+                "recursion in an `async fn` requires boxing"
+            );
+            diag.note("a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future");
+            diag.note(
+                "consider using the `async_recursion` crate: https://crates.io/crates/async_recursion",
+            );
+            let mut called = false;
+            for (i, frame) in cycle_error.cycle.iter().enumerate() {
+                if frame.query.dep_kind != dep_kinds::layout_of {
+                    continue;
+                }
+                let Some(frame_def_id) = frame.query.ty_def_id else {
+                    continue;
+                };
+                if !matches!(tcx.def_kind(frame_def_id), DefKind::Coroutine) {
+                    continue;
+                }
+                let frame_span = frame
+                    .query
+                    .default_span(cycle_error.cycle[(i + 1) % cycle_error.cycle.len()].span);
+                if frame_span.is_dummy() {
+                    continue;
+                }
+                diag.span_label(frame_span, if called { "...which calls this" } else { "recursive call here" });
+                called = true;
+            }
+            diag.emit()
         } else {
             report_cycle(tcx.sess, cycle_error).emit()
         };
diff --git a/tests/ui/async-await/in-trait/async-recursive-generic.stderr b/tests/ui/async-await/in-trait/async-recursive-generic.stderr
@@ -2,9 +2,12 @@ error[E0733]: recursion in an `async fn` requires boxing
   --> $DIR/async-recursive-generic.rs:8:5
    |
 LL |     async fn foo_recursive(&self, n: usize) -> T {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |             self.foo_recursive(n - 1).await
+   |             ------------------------------- recursive call here
    |
-   = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
+   = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
 
 error: aborting due to previous error
diff --git a/tests/ui/async-await/in-trait/async-recursive.stderr b/tests/ui/async-await/in-trait/async-recursive.stderr
@@ -2,9 +2,12 @@ error[E0733]: recursion in an `async fn` requires boxing
   --> $DIR/async-recursive.rs:8:5
    |
 LL |     async fn foo_recursive(&self, n: usize) -> i32 {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |             self.foo_recursive(n - 1).await
+   |             ------------------------------- recursive call here
    |
-   = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
+   = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
 
 error: aborting due to previous error
diff --git a/tests/ui/async-await/in-trait/indirect-recursion-issue-112047.stderr b/tests/ui/async-await/in-trait/indirect-recursion-issue-112047.stderr
@@ -2,9 +2,9 @@ error[E0733]: recursion in an `async fn` requires boxing
   --> $DIR/indirect-recursion-issue-112047.rs:32:5
    |
 LL |     async fn second(self) {
-   |     ^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
+   |     ^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
+   = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
 
 error: aborting due to previous error
diff --git a/tests/ui/async-await/mutually-recursive-async-impl-trait-type.stderr b/tests/ui/async-await/mutually-recursive-async-impl-trait-type.stderr
@@ -2,9 +2,14 @@ error[E0733]: recursion in an `async fn` requires boxing
   --> $DIR/mutually-recursive-async-impl-trait-type.rs:5:1
    |
 LL | async fn rec_1() {
-   | ^^^^^^^^^^^^^^^^ recursive `async fn`
+   | ^^^^^^^^^^^^^^^^
+LL |     rec_2().await;
+   |     ------------- recursive call here
+...
+LL |     rec_1().await;
+   |     ------------- ...which calls this
    |
-   = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
+   = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
 
 error: aborting due to previous error
diff --git a/tests/ui/async-await/recursive-async-impl-trait-type.stderr b/tests/ui/async-await/recursive-async-impl-trait-type.stderr
@@ -2,9 +2,12 @@ error[E0733]: recursion in an `async fn` requires boxing
   --> $DIR/recursive-async-impl-trait-type.rs:5:1
    |
 LL | async fn recursive_async_function() -> () {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |
+LL |     recursive_async_function().await;
+   |     -------------------------------- recursive call here
    |
-   = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
+   = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
 
 error: aborting due to previous error
diff --git a/tests/ui/impl-trait/recursive-impl-trait-type-indirect.stderr b/tests/ui/impl-trait/recursive-impl-trait-type-indirect.stderr
@@ -113,9 +113,12 @@ error[E0733]: recursion in an `async fn` requires boxing
   --> $DIR/recursive-impl-trait-type-indirect.rs:73:5
    |
 LL |     move || {
-   |     ^^^^^^^ recursive `async fn`
+   |     ^^^^^^^
+LL |
+LL |         let x = coroutine_hold();
+   |             - recursive call here
    |
-   = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
+   = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
 
 error[E0720]: cannot resolve opaque type
diff --git a/tests/ui/type-alias-impl-trait/indirect-recursion-issue-112047.stderr b/tests/ui/type-alias-impl-trait/indirect-recursion-issue-112047.stderr
@@ -1,10 +1,15 @@
 error[E0733]: recursion in an `async fn` requires boxing
   --> $DIR/indirect-recursion-issue-112047.rs:21:9
    |
+LL |     t.recur().await;
+   |     --------------- ...which calls this
+...
 LL |         async move { recur(self).await; }
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
+   |         ^^^^^^^^^^^^^-----------------^^^
+   |                      |
+   |                      recursive call here
    |
-   = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
+   = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
 
 error: aborting due to previous error

Original file line number	Diff line number	Diff line change
`@@ -1531,7 +1531,10 @@ pub enum CoroutineKind {`
`1531`	`1531`
`1532`	`1532`	`impl CoroutineKind {`
`1533`	`1533`	`pub fn is_fn_like(self) -> bool {`
`1534`		`- matches!(self, CoroutineKind::Async(CoroutineSource::Fn) \| CoroutineKind::Gen(CoroutineSource::Fn))`
	`1534`	`+ matches!(`
	`1535`	`+ self,`
	`1536`	`+ CoroutineKind::Async(CoroutineSource::Fn) \| CoroutineKind::Gen(CoroutineSource::Fn)`
	`1537`	`+ )`
`1535`	`1538`	`}`
`1536`	`1539`	`}`
`1537`	`1540`
Original file line number	Diff line number	Diff line change
@@ -2,9 +2,12 @@ error[E0733]: recursion in an `async fn` requires boxing
`2`	`2`	`--> $DIR/async-recursive-generic.rs:8:5`
`3`	`3`	`\|`
`4`	`4`	`LL \| async fn foo_recursive(&self, n: usize) -> T {`
`5`		- \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
	`5`	`+ \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^`
	`6`	`+...`
	`7`	`+LL \| self.foo_recursive(n - 1).await`
	`8`	`+ \| ------------------------------- recursive call here`
`6`	`9`	`\|`
`7`		- = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
	`10`	+ = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
`8`	`11`	= note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
`9`	`12`
`10`	`13`	`error: aborting due to previous error`
Original file line number	Diff line number	Diff line change
@@ -2,9 +2,12 @@ error[E0733]: recursion in an `async fn` requires boxing
`2`	`2`	`--> $DIR/async-recursive.rs:8:5`
`3`	`3`	`\|`
`4`	`4`	`LL \| async fn foo_recursive(&self, n: usize) -> i32 {`
`5`		- \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
	`5`	`+ \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^`
	`6`	`+...`
	`7`	`+LL \| self.foo_recursive(n - 1).await`
	`8`	`+ \| ------------------------------- recursive call here`
`6`	`9`	`\|`
`7`		- = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
	`10`	+ = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
`8`	`11`	= note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
`9`	`12`
`10`	`13`	`error: aborting due to previous error`
Original file line number	Diff line number	Diff line change
@@ -2,9 +2,9 @@ error[E0733]: recursion in an `async fn` requires boxing
`2`	`2`	`--> $DIR/indirect-recursion-issue-112047.rs:32:5`
`3`	`3`	`\|`
`4`	`4`	`LL \| async fn second(self) {`
`5`		- \| ^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
	`5`	`+ \| ^^^^^^^^^^^^^^^^^^^^^`
`6`	`6`	`\|`
`7`		- = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
	`7`	+ = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
`8`	`8`	= note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
`9`	`9`
`10`	`10`	`error: aborting due to previous error`
Original file line number	Diff line number	Diff line change
@@ -2,9 +2,12 @@ error[E0733]: recursion in an `async fn` requires boxing
`2`	`2`	`--> $DIR/recursive-async-impl-trait-type.rs:5:1`
`3`	`3`	`\|`
`4`	`4`	`LL \| async fn recursive_async_function() -> () {`
`5`		- \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ recursive `async fn`
	`5`	`+ \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^`
	`6`	`+LL \|`
	`7`	`+LL \| recursive_async_function().await;`
	`8`	`+ \| -------------------------------- recursive call here`
`6`	`9`	`\|`
`7`		- = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
	`10`	+ = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
`8`	`11`	= note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
`9`	`12`
`10`	`13`	`error: aborting due to previous error`
Original file line number	Diff line number	Diff line change
@@ -113,9 +113,12 @@ error[E0733]: recursion in an `async fn` requires boxing
`113`	`113`	`--> $DIR/recursive-impl-trait-type-indirect.rs:73:5`
`114`	`114`	`\|`
`115`	`115`	`LL \| move \|\| {`
`116`		- \| ^^^^^^^ recursive `async fn`
	`116`	`+ \| ^^^^^^^`
	`117`	`+LL \|`
	`118`	`+LL \| let x = coroutine_hold();`
	`119`	`+ \| - recursive call here`
`117`	`120`	`\|`
`118`		- = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
	`121`	+ = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
`119`	`122`	= note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
`120`	`123`
`121`	`124`	`error[E0720]: cannot resolve opaque type`