Avoid cycle with projections from object types

Normalizing `<dyn Iterator<Item = ()> as Iterator>::Item` no longer
requires selecting `dyn Iterator<Item = ()>: Iterator`. This was
previously worked around by using a special type-folder to normalize
things.

8 files changed, 73 insertions, 83 deletions

diff --git a/src/test/ui/regions/regions-enum-not-wf.rs b/src/test/ui/regions/regions-enum-not-wf.rs
index 781cdb7286a..6de08f66d75 100644
--- a/src/test/ui/regions/regions-enum-not-wf.rs
+++ b/src/test/ui/regions/regions-enum-not-wf.rs
@@ -5,17 +5,18 @@
 #![allow(dead_code)]
 
 trait Dummy<'a> {
-  type Out;
+    type Out;
 }
 impl<'a, T> Dummy<'a> for T
-where T: 'a
+where
+    T: 'a,
 {
-  type Out = ();
+    type Out = ();
 }
 type RequireOutlives<'a, T> = <T as Dummy<'a>>::Out;
 
 enum Ref1<'a, T> {
-    Ref1Variant1(RequireOutlives<'a, T>) //~ ERROR the parameter type `T` may not live long enough
+    Ref1Variant1(RequireOutlives<'a, T>), //~ ERROR the parameter type `T` may not live long enough
 }
 
 enum Ref2<'a, T> {
@@ -23,18 +24,18 @@ enum Ref2<'a, T> {
     Ref2Variant2(isize, RequireOutlives<'a, T>), //~ ERROR the parameter type `T` may not live long enough
 }
 
-enum RefOk<'a, T:'a> {
-    RefOkVariant1(&'a T)
+enum RefOk<'a, T: 'a> {
+    RefOkVariant1(&'a T),
 }
 
 // This is now well formed. RFC 2093
 enum RefIndirect<'a, T> {
-    RefIndirectVariant1(isize, RefOk<'a,T>)
+    RefIndirectVariant1(isize, RefOk<'a, T>),
 }
 
-enum RefDouble<'a, 'b, T> { //~ ERROR the parameter type `T` may not live long enough [E0309]
-    RefDoubleVariant1(&'a RequireOutlives<'b, T>)
-        //~^ the parameter type `T` may not live long enough [E0309]
+enum RefDouble<'a, 'b, T> {
+    RefDoubleVariant1(&'a RequireOutlives<'b, T>),
+    //~^ the parameter type `T` may not live long enough [E0309]
 }
 
-fn main() { }
+fn main() {}
diff --git a/src/test/ui/regions/regions-enum-not-wf.stderr b/src/test/ui/regions/regions-enum-not-wf.stderr
index e32a36f72cd..36686eaf92f 100644
--- a/src/test/ui/regions/regions-enum-not-wf.stderr
+++ b/src/test/ui/regions/regions-enum-not-wf.stderr
@@ -1,13 +1,13 @@
 error[E0309]: the parameter type `T` may not live long enough
-  --> $DIR/regions-enum-not-wf.rs:18:18
+  --> $DIR/regions-enum-not-wf.rs:19:18
    |
 LL | enum Ref1<'a, T> {
    |               - help: consider adding an explicit lifetime bound...: `T: 'a`
-LL |     Ref1Variant1(RequireOutlives<'a, T>)
+LL |     Ref1Variant1(RequireOutlives<'a, T>),
    |                  ^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
 
 error[E0309]: the parameter type `T` may not live long enough
-  --> $DIR/regions-enum-not-wf.rs:23:25
+  --> $DIR/regions-enum-not-wf.rs:24:25
    |
 LL | enum Ref2<'a, T> {
    |               - help: consider adding an explicit lifetime bound...: `T: 'a`
@@ -16,25 +16,13 @@ LL |     Ref2Variant2(isize, RequireOutlives<'a, T>),
    |                         ^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
 
 error[E0309]: the parameter type `T` may not live long enough
-  --> $DIR/regions-enum-not-wf.rs:35:1
-   |
-LL |   enum RefDouble<'a, 'b, T> {
-   |   ^                      - help: consider adding an explicit lifetime bound...: `T: 'b`
-   |  _|
-   | |
-LL | |     RefDoubleVariant1(&'a RequireOutlives<'b, T>)
-LL | |
-LL | | }
-   | |_^ ...so that the type `T` will meet its required lifetime bounds
-
-error[E0309]: the parameter type `T` may not live long enough
-  --> $DIR/regions-enum-not-wf.rs:36:23
+  --> $DIR/regions-enum-not-wf.rs:37:23
    |
 LL | enum RefDouble<'a, 'b, T> {
    |                        - help: consider adding an explicit lifetime bound...: `T: 'b`
-LL |     RefDoubleVariant1(&'a RequireOutlives<'b, T>)
+LL |     RefDoubleVariant1(&'a RequireOutlives<'b, T>),
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0309`.
diff --git a/src/test/ui/regions/regions-normalize-in-where-clause-list.rs b/src/test/ui/regions/regions-normalize-in-where-clause-list.rs
index e912805d855..9912e88c2ec 100644
--- a/src/test/ui/regions/regions-normalize-in-where-clause-list.rs
+++ b/src/test/ui/regions/regions-normalize-in-where-clause-list.rs
@@ -6,7 +6,8 @@ trait Project<'a, 'b> {
 }
 
 impl<'a, 'b> Project<'a, 'b> for ()
-    where 'a: 'b
+where
+    'a: 'b,
 {
     type Item = ();
 }
@@ -14,16 +15,18 @@ impl<'a, 'b> Project<'a, 'b> for ()
 // No error here, we have 'a: 'b. We used to report an error here
 // though, see https://github.com/rust-lang/rust/issues/45937.
 fn foo<'a: 'b, 'b>()
-    where <() as Project<'a, 'b>>::Item : Eq
+where
+    <() as Project<'a, 'b>>::Item: Eq,
 {
 }
 
 // Here we get an error: we need `'a: 'b`.
-fn bar<'a, 'b>() //~ ERROR cannot infer
-                 //~| ERROR cannot infer
-                 //~| ERROR cannot infer
-    where <() as Project<'a, 'b>>::Item : Eq
+fn bar<'a, 'b>()
+//~^ ERROR cannot infer
+//~| ERROR cannot infer
+where
+    <() as Project<'a, 'b>>::Item: Eq,
 {
 }
 
-fn main() { }
+fn main() {}
diff --git a/src/test/ui/regions/regions-normalize-in-where-clause-list.stderr b/src/test/ui/regions/regions-normalize-in-where-clause-list.stderr
index 10ecb8d5262..24bf64261e9 100644
--- a/src/test/ui/regions/regions-normalize-in-where-clause-list.stderr
+++ b/src/test/ui/regions/regions-normalize-in-where-clause-list.stderr
@@ -1,5 +1,5 @@
 error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
-  --> $DIR/regions-normalize-in-where-clause-list.rs:22:1
+  --> $DIR/regions-normalize-in-where-clause-list.rs:24:1
    |
 LL | / fn bar<'a, 'b>()
 LL | |
@@ -7,18 +7,18 @@ LL | |
 LL | |     where <() as Project<'a, 'b>>::Item : Eq
    | |____________________________________________^
    |
-note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 22:8...
-  --> $DIR/regions-normalize-in-where-clause-list.rs:22:8
+note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 24:8...
+  --> $DIR/regions-normalize-in-where-clause-list.rs:24:8
    |
 LL | fn bar<'a, 'b>()
    |        ^^
-note: ...but the lifetime must also be valid for the lifetime `'b` as defined on the function body at 22:12...
-  --> $DIR/regions-normalize-in-where-clause-list.rs:22:12
+note: ...but the lifetime must also be valid for the lifetime `'b` as defined on the function body at 24:12...
+  --> $DIR/regions-normalize-in-where-clause-list.rs:24:12
    |
 LL | fn bar<'a, 'b>()
    |            ^^
 note: ...so that the types are compatible
-  --> $DIR/regions-normalize-in-where-clause-list.rs:22:1
+  --> $DIR/regions-normalize-in-where-clause-list.rs:24:1
    |
 LL | / fn bar<'a, 'b>()
 LL | |
@@ -64,24 +64,24 @@ error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` d
 LL | fn bar<'a, 'b>()
    |    ^^^
    |
-note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 22:8...
-  --> $DIR/regions-normalize-in-where-clause-list.rs:22:8
+note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 24:8...
+  --> $DIR/regions-normalize-in-where-clause-list.rs:24:8
    |
 LL | fn bar<'a, 'b>()
    |        ^^
-note: ...but the lifetime must also be valid for the lifetime `'b` as defined on the function body at 22:12...
-  --> $DIR/regions-normalize-in-where-clause-list.rs:22:12
+note: ...but the lifetime must also be valid for the lifetime `'b` as defined on the function body at 24:12...
+  --> $DIR/regions-normalize-in-where-clause-list.rs:24:12
    |
 LL | fn bar<'a, 'b>()
    |            ^^
 note: ...so that the types are compatible
-  --> $DIR/regions-normalize-in-where-clause-list.rs:22:4
+  --> $DIR/regions-normalize-in-where-clause-list.rs:24:4
    |
 LL | fn bar<'a, 'b>()
    |    ^^^
    = note: expected `Project<'a, 'b>`
               found `Project<'_, '_>`
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0495`.
diff --git a/src/test/ui/rfc-2093-infer-outlives/regions-enum-not-wf.rs b/src/test/ui/rfc-2093-infer-outlives/regions-enum-not-wf.rs
index 781cdb7286a..6de08f66d75 100644
--- a/src/test/ui/rfc-2093-infer-outlives/regions-enum-not-wf.rs
+++ b/src/test/ui/rfc-2093-infer-outlives/regions-enum-not-wf.rs
@@ -5,17 +5,18 @@
 #![allow(dead_code)]
 
 trait Dummy<'a> {
-  type Out;
+    type Out;
 }
 impl<'a, T> Dummy<'a> for T
-where T: 'a
+where
+    T: 'a,
 {
-  type Out = ();
+    type Out = ();
 }
 type RequireOutlives<'a, T> = <T as Dummy<'a>>::Out;
 
 enum Ref1<'a, T> {
-    Ref1Variant1(RequireOutlives<'a, T>) //~ ERROR the parameter type `T` may not live long enough
+    Ref1Variant1(RequireOutlives<'a, T>), //~ ERROR the parameter type `T` may not live long enough
 }
 
 enum Ref2<'a, T> {
@@ -23,18 +24,18 @@ enum Ref2<'a, T> {
     Ref2Variant2(isize, RequireOutlives<'a, T>), //~ ERROR the parameter type `T` may not live long enough
 }
 
-enum RefOk<'a, T:'a> {
-    RefOkVariant1(&'a T)
+enum RefOk<'a, T: 'a> {
+    RefOkVariant1(&'a T),
 }
 
 // This is now well formed. RFC 2093
 enum RefIndirect<'a, T> {
-    RefIndirectVariant1(isize, RefOk<'a,T>)
+    RefIndirectVariant1(isize, RefOk<'a, T>),
 }
 
-enum RefDouble<'a, 'b, T> { //~ ERROR the parameter type `T` may not live long enough [E0309]
-    RefDoubleVariant1(&'a RequireOutlives<'b, T>)
-        //~^ the parameter type `T` may not live long enough [E0309]
+enum RefDouble<'a, 'b, T> {
+    RefDoubleVariant1(&'a RequireOutlives<'b, T>),
+    //~^ the parameter type `T` may not live long enough [E0309]
 }
 
-fn main() { }
+fn main() {}
diff --git a/src/test/ui/rfc-2093-infer-outlives/regions-enum-not-wf.stderr b/src/test/ui/rfc-2093-infer-outlives/regions-enum-not-wf.stderr
index e32a36f72cd..36686eaf92f 100644
--- a/src/test/ui/rfc-2093-infer-outlives/regions-enum-not-wf.stderr
+++ b/src/test/ui/rfc-2093-infer-outlives/regions-enum-not-wf.stderr
@@ -1,13 +1,13 @@
 error[E0309]: the parameter type `T` may not live long enough
-  --> $DIR/regions-enum-not-wf.rs:18:18
+  --> $DIR/regions-enum-not-wf.rs:19:18
    |
 LL | enum Ref1<'a, T> {
    |               - help: consider adding an explicit lifetime bound...: `T: 'a`
-LL |     Ref1Variant1(RequireOutlives<'a, T>)
+LL |     Ref1Variant1(RequireOutlives<'a, T>),
    |                  ^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
 
 error[E0309]: the parameter type `T` may not live long enough
-  --> $DIR/regions-enum-not-wf.rs:23:25
+  --> $DIR/regions-enum-not-wf.rs:24:25
    |
 LL | enum Ref2<'a, T> {
    |               - help: consider adding an explicit lifetime bound...: `T: 'a`
@@ -16,25 +16,13 @@ LL |     Ref2Variant2(isize, RequireOutlives<'a, T>),
    |                         ^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
 
 error[E0309]: the parameter type `T` may not live long enough
-  --> $DIR/regions-enum-not-wf.rs:35:1
-   |
-LL |   enum RefDouble<'a, 'b, T> {
-   |   ^                      - help: consider adding an explicit lifetime bound...: `T: 'b`
-   |  _|
-   | |
-LL | |     RefDoubleVariant1(&'a RequireOutlives<'b, T>)
-LL | |
-LL | | }
-   | |_^ ...so that the type `T` will meet its required lifetime bounds
-
-error[E0309]: the parameter type `T` may not live long enough
-  --> $DIR/regions-enum-not-wf.rs:36:23
+  --> $DIR/regions-enum-not-wf.rs:37:23
    |
 LL | enum RefDouble<'a, 'b, T> {
    |                        - help: consider adding an explicit lifetime bound...: `T: 'b`
-LL |     RefDoubleVariant1(&'a RequireOutlives<'b, T>)
+LL |     RefDoubleVariant1(&'a RequireOutlives<'b, T>),
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0309`.
diff --git a/src/test/ui/traits/cycle-cache-err-60010.rs b/src/test/ui/traits/cycle-cache-err-60010.rs
index 62d558fde88..98bfcb8d67b 100644
--- a/src/test/ui/traits/cycle-cache-err-60010.rs
+++ b/src/test/ui/traits/cycle-cache-err-60010.rs
@@ -24,7 +24,7 @@ struct Runtime<DB: Database> {
     _storage: Box<DB::Storage>,
 }
 struct SalsaStorage {
-    _parse: <ParseQuery as Query<RootDatabase>>::Data, //~ ERROR overflow
+    _parse: <ParseQuery as Query<RootDatabase>>::Data,
 }
 
 impl Database for RootDatabase {
@@ -67,6 +67,7 @@ pub(crate) fn goto_implementation(db: &RootDatabase) -> u32 {
     // we used to fail to report an error here because we got the
     // caching wrong.
     SourceDatabase::parse(db);
+    //~^ ERROR overflow
     22
 }
 
diff --git a/src/test/ui/traits/cycle-cache-err-60010.stderr b/src/test/ui/traits/cycle-cache-err-60010.stderr
index 25b1f427f3a..738b052a11e 100644
--- a/src/test/ui/traits/cycle-cache-err-60010.stderr
+++ b/src/test/ui/traits/cycle-cache-err-60010.stderr
@@ -1,10 +1,18 @@
-error[E0275]: overflow evaluating the requirement `RootDatabase: SourceDatabase`
-  --> $DIR/cycle-cache-err-60010.rs:27:13
+error[E0275]: overflow evaluating the requirement `SalsaStorage: std::panic::RefUnwindSafe`
+  --> $DIR/cycle-cache-err-60010.rs:69:5
    |
-LL |     _parse: <ParseQuery as Query<RootDatabase>>::Data,
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     fn parse(&self) {
+   |     --------------- required by `SourceDatabase::parse`
+...
+LL |     SourceDatabase::parse(db);
+   |     ^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: required because of the requirements on the impl of `Query<RootDatabase>` for `ParseQuery`
+   = note: required because it appears within the type `*const SalsaStorage`
+   = note: required because it appears within the type `std::ptr::Unique<SalsaStorage>`
+   = note: required because it appears within the type `std::boxed::Box<SalsaStorage>`
+   = note: required because it appears within the type `Runtime<RootDatabase>`
+   = note: required because it appears within the type `RootDatabase`
+   = note: required because of the requirements on the impl of `SourceDatabase` for `RootDatabase`
 
 error[E0275]: overflow evaluating the requirement `Runtime<RootDatabase>: RefUnwindSafe`
   --> $DIR/cycle-cache-err-60010.rs:31:20