Rollup merge of #100652 - compiler-errors:no-defer-sized-checks, r=TaKO8Ki

Remove deferred sized checks (make them eager)

Improves diagnostics spans... this doesn't seem to be the case anymore:

```rust
// Some additional `Sized` obligations badly affect type inference.
// These obligations are added in a later stage of typeck.
pub(super) deferred_sized_obligations:
        RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
```

14 files changed, 37 insertions, 107 deletions

diff --git a/compiler/rustc_typeck/src/check/expr.rs b/compiler/rustc_typeck/src/check/expr.rs
index c82c819169d..5ff62f36b45 100644
--- a/compiler/rustc_typeck/src/check/expr.rs
+++ b/compiler/rustc_typeck/src/check/expr.rs
@@ -561,16 +561,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // We just want to check sizedness, so instead of introducing
                     // placeholder lifetimes with probing, we just replace higher lifetimes
                     // with fresh vars.
-                    let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
+                    let arg_span = args.get(i).map(|a| a.span);
+                    let span = arg_span.unwrap_or(expr.span);
                     let input = self.replace_bound_vars_with_fresh_vars(
                         span,
                         infer::LateBoundRegionConversionTime::FnCall,
                         fn_sig.input(i),
                     );
-                    self.require_type_is_sized_deferred(
-                        input,
+                    self.require_type_is_sized(
+                        self.normalize_associated_types_in(span, input),
                         span,
-                        traits::SizedArgumentType(None),
+                        traits::SizedArgumentType(arg_span),
                     );
                 }
             }
@@ -585,7 +586,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 infer::LateBoundRegionConversionTime::FnCall,
                 fn_sig.output(),
             );
-            self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
+            self.require_type_is_sized(
+                self.normalize_associated_types_in(expr.span, output),
+                expr.span,
+                traits::SizedReturnType,
+            );
         }
 
         // We always require that the type provided as the value for
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
index 3a809334511..1d9d04ceec0 100644
--- a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
+++ b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
@@ -442,17 +442,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    pub fn require_type_is_sized_deferred(
-        &self,
-        ty: Ty<'tcx>,
-        span: Span,
-        code: traits::ObligationCauseCode<'tcx>,
-    ) {
-        if !ty.references_error() {
-            self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
-        }
-    }
-
     pub fn register_bound(
         &self,
         ty: Ty<'tcx>,
diff --git a/compiler/rustc_typeck/src/check/inherited.rs b/compiler/rustc_typeck/src/check/inherited.rs
index cd152eb97f1..f3115fc5c02 100644
--- a/compiler/rustc_typeck/src/check/inherited.rs
+++ b/compiler/rustc_typeck/src/check/inherited.rs
@@ -35,11 +35,6 @@ pub struct Inherited<'a, 'tcx> {
 
     pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
 
-    // Some additional `Sized` obligations badly affect type inference.
-    // These obligations are added in a later stage of typeck.
-    pub(super) deferred_sized_obligations:
-        RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
-
     // When we process a call like `c()` where `c` is a closure type,
     // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
     // `FnOnce` closure. In that case, we defer full resolution of the
@@ -117,7 +112,6 @@ impl<'a, 'tcx> Inherited<'a, 'tcx> {
             infcx,
             fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
             locals: RefCell::new(Default::default()),
-            deferred_sized_obligations: RefCell::new(Vec::new()),
             deferred_call_resolutions: RefCell::new(Default::default()),
             deferred_cast_checks: RefCell::new(Vec::new()),
             deferred_transmute_checks: RefCell::new(Vec::new()),
diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs
index 1b50209ee64..dfbef544b1d 100644
--- a/compiler/rustc_typeck/src/check/mod.rs
+++ b/compiler/rustc_typeck/src/check/mod.rs
@@ -467,11 +467,6 @@ fn typeck_with_fallback<'tcx>(
         fcx.resolve_rvalue_scopes(def_id.to_def_id());
         fcx.resolve_generator_interiors(def_id.to_def_id());
 
-        for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
-            let ty = fcx.normalize_ty(span, ty);
-            fcx.require_type_is_sized(ty, span, code);
-        }
-
         fcx.select_all_obligations_or_error();
 
         if !fcx.infcx.is_tainted_by_errors() {
diff --git a/src/test/incremental/const-generics/hash-tyvid-regression-1.rs b/src/test/incremental/const-generics/hash-tyvid-regression-1.rs
index 5ff7b19d894..53358b183cb 100644
--- a/src/test/incremental/const-generics/hash-tyvid-regression-1.rs
+++ b/src/test/incremental/const-generics/hash-tyvid-regression-1.rs
@@ -9,7 +9,6 @@ where
     use std::convert::TryFrom;
     <[T; N.get()]>::try_from(())
     //~^ error: the trait bound
-    //~| error: the trait bound
     //~| error: mismatched types
 }
 
diff --git a/src/test/ui/associated-types/associated-types-path-2.stderr b/src/test/ui/associated-types/associated-types-path-2.stderr
index c37d469890c..66f1ab72692 100644
--- a/src/test/ui/associated-types/associated-types-path-2.stderr
+++ b/src/test/ui/associated-types/associated-types-path-2.stderr
@@ -33,7 +33,9 @@ error[E0277]: the trait bound `u32: Foo` is not satisfied
   --> $DIR/associated-types-path-2.rs:29:14
    |
 LL |     f1(2u32, 4u32);
-   |              ^^^^ the trait `Foo` is not implemented for `u32`
+   |     --       ^^^^ the trait `Foo` is not implemented for `u32`
+   |     |
+   |     required by a bound introduced by this call
    |
    = help: the trait `Foo` is implemented for `i32`
 
diff --git a/src/test/ui/feature-gates/feature-gate-unsized_fn_params.stderr b/src/test/ui/feature-gates/feature-gate-unsized_fn_params.stderr
index 0f7520ef7f8..0557340f792 100644
--- a/src/test/ui/feature-gates/feature-gate-unsized_fn_params.stderr
+++ b/src/test/ui/feature-gates/feature-gate-unsized_fn_params.stderr
@@ -15,11 +15,16 @@ error[E0277]: the size for values of type `(dyn Foo + 'static)` cannot be known
   --> $DIR/feature-gate-unsized_fn_params.rs:24:9
    |
 LL |     foo(*x);
-   |         ^^ doesn't have a size known at compile-time
+   |     --- ^^ doesn't have a size known at compile-time
+   |     |
+   |     required by a bound introduced by this call
    |
    = help: the trait `Sized` is not implemented for `(dyn Foo + 'static)`
-   = note: all function arguments must have a statically known size
    = help: unsized fn params are gated as an unstable feature
+help: function arguments must have a statically known size, borrowed types always have a known size
+   |
+LL |     foo(&*x);
+   |         +
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/iterators/issue-28098.rs b/src/test/ui/iterators/issue-28098.rs
index 62a90d90d12..c4addaccefc 100644
--- a/src/test/ui/iterators/issue-28098.rs
+++ b/src/test/ui/iterators/issue-28098.rs
@@ -1,7 +1,6 @@
 fn main() {
     let _ = Iterator::next(&mut ());
     //~^ ERROR `()` is not an iterator
-    //~| ERROR `()` is not an iterator
 
     for _ in false {}
     //~^ ERROR `bool` is not an iterator
@@ -17,7 +16,6 @@ pub fn other() {
 
     let _ = Iterator::next(&mut ());
     //~^ ERROR `()` is not an iterator
-    //~| ERROR `()` is not an iterator
 
     let _ = Iterator::next(&mut ());
     //~^ ERROR `()` is not an iterator
diff --git a/src/test/ui/iterators/issue-28098.stderr b/src/test/ui/iterators/issue-28098.stderr
index 3beb9929244..e7128248f93 100644
--- a/src/test/ui/iterators/issue-28098.stderr
+++ b/src/test/ui/iterators/issue-28098.stderr
@@ -9,7 +9,7 @@ LL |     let _ = Iterator::next(&mut ());
    = help: the trait `Iterator` is not implemented for `()`
 
 error[E0277]: `bool` is not an iterator
-  --> $DIR/issue-28098.rs:6:14
+  --> $DIR/issue-28098.rs:5:14
    |
 LL |     for _ in false {}
    |              ^^^^^ `bool` is not an iterator
@@ -18,7 +18,7 @@ LL |     for _ in false {}
    = note: required because of the requirements on the impl of `IntoIterator` for `bool`
 
 error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:9:28
+  --> $DIR/issue-28098.rs:8:28
    |
 LL |     let _ = Iterator::next(&mut ());
    |             -------------- ^^^^^^^ `()` is not an iterator
@@ -28,15 +28,7 @@ LL |     let _ = Iterator::next(&mut ());
    = help: the trait `Iterator` is not implemented for `()`
 
 error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:2:13
-   |
-LL |     let _ = Iterator::next(&mut ());
-   |             ^^^^^^^^^^^^^^ `()` is not an iterator
-   |
-   = help: the trait `Iterator` is not implemented for `()`
-
-error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:18:28
+  --> $DIR/issue-28098.rs:17:28
    |
 LL |     let _ = Iterator::next(&mut ());
    |             -------------- ^^^^^^^ `()` is not an iterator
@@ -46,7 +38,7 @@ LL |     let _ = Iterator::next(&mut ());
    = help: the trait `Iterator` is not implemented for `()`
 
 error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:22:28
+  --> $DIR/issue-28098.rs:20:28
    |
 LL |     let _ = Iterator::next(&mut ());
    |             -------------- ^^^^^^^ `()` is not an iterator
@@ -56,7 +48,7 @@ LL |     let _ = Iterator::next(&mut ());
    = help: the trait `Iterator` is not implemented for `()`
 
 error[E0277]: `bool` is not an iterator
-  --> $DIR/issue-28098.rs:25:14
+  --> $DIR/issue-28098.rs:23:14
    |
 LL |     for _ in false {}
    |              ^^^^^ `bool` is not an iterator
@@ -64,14 +56,6 @@ LL |     for _ in false {}
    = help: the trait `Iterator` is not implemented for `bool`
    = note: required because of the requirements on the impl of `IntoIterator` for `bool`
 
-error[E0277]: `()` is not an iterator
-  --> $DIR/issue-28098.rs:18:13
-   |
-LL |     let _ = Iterator::next(&mut ());
-   |             ^^^^^^^^^^^^^^ `()` is not an iterator
-   |
-   = help: the trait `Iterator` is not implemented for `()`
-
-error: aborting due to 8 previous errors
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/on-unimplemented/multiple-impls.rs b/src/test/ui/on-unimplemented/multiple-impls.rs
index b74957ebcd4..79c40f650db 100644
--- a/src/test/ui/on-unimplemented/multiple-impls.rs
+++ b/src/test/ui/on-unimplemented/multiple-impls.rs
@@ -32,11 +32,8 @@ impl Index<Bar<usize>> for [i32] {
 fn main() {
     Index::index(&[] as &[i32], 2u32);
     //~^ ERROR E0277
-    //~| ERROR E0277
     Index::index(&[] as &[i32], Foo(2u32));
     //~^ ERROR E0277
-    //~| ERROR E0277
     Index::index(&[] as &[i32], Bar(2u32));
     //~^ ERROR E0277
-    //~| ERROR E0277
 }
diff --git a/src/test/ui/on-unimplemented/multiple-impls.stderr b/src/test/ui/on-unimplemented/multiple-impls.stderr
index 06e1a222af8..6e3601d7bf4 100644
--- a/src/test/ui/on-unimplemented/multiple-impls.stderr
+++ b/src/test/ui/on-unimplemented/multiple-impls.stderr
@@ -12,7 +12,7 @@ LL |     Index::index(&[] as &[i32], 2u32);
              <[i32] as Index<Foo<usize>>>
 
 error[E0277]: the trait bound `[i32]: Index<Foo<u32>>` is not satisfied
-  --> $DIR/multiple-impls.rs:36:18
+  --> $DIR/multiple-impls.rs:35:18
    |
 LL |     Index::index(&[] as &[i32], Foo(2u32));
    |     ------------ ^^^^^^^^^^^^^ on impl for Foo
@@ -25,7 +25,7 @@ LL |     Index::index(&[] as &[i32], Foo(2u32));
              <[i32] as Index<Foo<usize>>>
 
 error[E0277]: the trait bound `[i32]: Index<Bar<u32>>` is not satisfied
-  --> $DIR/multiple-impls.rs:39:18
+  --> $DIR/multiple-impls.rs:37:18
    |
 LL |     Index::index(&[] as &[i32], Bar(2u32));
    |     ------------ ^^^^^^^^^^^^^ on impl for Bar
@@ -37,39 +37,6 @@ LL |     Index::index(&[] as &[i32], Bar(2u32));
              <[i32] as Index<Bar<usize>>>
              <[i32] as Index<Foo<usize>>>
 
-error[E0277]: the trait bound `[i32]: Index<u32>` is not satisfied
-  --> $DIR/multiple-impls.rs:33:5
-   |
-LL |     Index::index(&[] as &[i32], 2u32);
-   |     ^^^^^^^^^^^^ trait message
-   |
-   = help: the trait `Index<u32>` is not implemented for `[i32]`
-   = help: the following other types implement trait `Index<Idx>`:
-             <[i32] as Index<Bar<usize>>>
-             <[i32] as Index<Foo<usize>>>
-
-error[E0277]: the trait bound `[i32]: Index<Foo<u32>>` is not satisfied
-  --> $DIR/multiple-impls.rs:36:5
-   |
-LL |     Index::index(&[] as &[i32], Foo(2u32));
-   |     ^^^^^^^^^^^^ on impl for Foo
-   |
-   = help: the trait `Index<Foo<u32>>` is not implemented for `[i32]`
-   = help: the following other types implement trait `Index<Idx>`:
-             <[i32] as Index<Bar<usize>>>
-             <[i32] as Index<Foo<usize>>>
-
-error[E0277]: the trait bound `[i32]: Index<Bar<u32>>` is not satisfied
-  --> $DIR/multiple-impls.rs:39:5
-   |
-LL |     Index::index(&[] as &[i32], Bar(2u32));
-   |     ^^^^^^^^^^^^ on impl for Bar
-   |
-   = help: the trait `Index<Bar<u32>>` is not implemented for `[i32]`
-   = help: the following other types implement trait `Index<Idx>`:
-             <[i32] as Index<Bar<usize>>>
-             <[i32] as Index<Foo<usize>>>
-
-error: aborting due to 6 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/on-unimplemented/on-impl.rs b/src/test/ui/on-unimplemented/on-impl.rs
index ab3e67d01fe..b03e1f7c6a8 100644
--- a/src/test/ui/on-unimplemented/on-impl.rs
+++ b/src/test/ui/on-unimplemented/on-impl.rs
@@ -21,5 +21,4 @@ impl Index<usize> for [i32] {
 fn main() {
     Index::<u32>::index(&[1, 2, 3] as &[i32], 2u32);
     //~^ ERROR E0277
-    //~| ERROR E0277
 }
diff --git a/src/test/ui/on-unimplemented/on-impl.stderr b/src/test/ui/on-unimplemented/on-impl.stderr
index 769a3d77a57..396c062cfe2 100644
--- a/src/test/ui/on-unimplemented/on-impl.stderr
+++ b/src/test/ui/on-unimplemented/on-impl.stderr
@@ -9,15 +9,6 @@ LL |     Index::<u32>::index(&[1, 2, 3] as &[i32], 2u32);
    = help: the trait `Index<u32>` is not implemented for `[i32]`
    = help: the trait `Index<usize>` is implemented for `[i32]`
 
-error[E0277]: the trait bound `[i32]: Index<u32>` is not satisfied
-  --> $DIR/on-impl.rs:22:5
-   |
-LL |     Index::<u32>::index(&[1, 2, 3] as &[i32], 2u32);
-   |     ^^^^^^^^^^^^^^^^^^^ a usize is required to index into a slice
-   |
-   = help: the trait `Index<u32>` is not implemented for `[i32]`
-   = help: the trait `Index<usize>` is implemented for `[i32]`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/unsized/issue-30355.stderr b/src/test/ui/unsized/issue-30355.stderr
index 71bbdf5dec7..d7af558eef4 100644
--- a/src/test/ui/unsized/issue-30355.stderr
+++ b/src/test/ui/unsized/issue-30355.stderr
@@ -2,11 +2,16 @@ error[E0277]: the size for values of type `[u8]` cannot be known at compilation
   --> $DIR/issue-30355.rs:5:8
    |
 LL |     &X(*Y)
-   |        ^^ doesn't have a size known at compile-time
+   |      - ^^ doesn't have a size known at compile-time
+   |      |
+   |      required by a bound introduced by this call
    |
    = help: the trait `Sized` is not implemented for `[u8]`
-   = note: all function arguments must have a statically known size
    = help: unsized fn params are gated as an unstable feature
+help: function arguments must have a statically known size, borrowed types always have a known size
+   |
+LL |     &X(&*Y)
+   |        +
 
 error: aborting due to previous error