[WIP] some mir typeck cleanup

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -511,6 +511,15 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
             place_ty = self.sanitize_projection(place_ty, elem, place, location);
         }
 
+        self.cx.prove_predicate(
+            ty::Binder::dummy(ty::PredicateKind::WellFormed(
+                self.body().local_decls[place.local].ty.into(),
+            ))
+            .to_predicate(self.tcx()),
+            location.to_locations(),
+            ConstraintCategory::Boring,
+        );
+
         if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context {
             let tcx = self.tcx();
             let trait_ref = ty::TraitRef {

src/test/ui/borrowck/issue-7573.rs

@@ -17,6 +17,8 @@ pub fn remove_package_from_database() {
         lines_to_use.push(installed_id);
         //~^ ERROR borrowed data escapes outside of closure
         //~| NOTE `installed_id` escapes the closure body here
+        //~| NOTE requirement occurs because of a mutable reference to `Vec<&CrateId>`
+        //~| NOTE mutable references are invariant over their type parameter
     };
     list_database(push_id);
 

src/test/ui/borrowck/issue-7573.stderr

@@ -9,6 +9,10 @@ LL |     let push_id = |installed_id: &CrateId| {
 LL |
 LL |         lines_to_use.push(installed_id);
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `installed_id` escapes the closure body here
+   |
+   = note: requirement occurs because of a mutable reference to `Vec<&CrateId>`
+   = note: mutable references are invariant over their type parameter
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: aborting due to previous error
 

src/test/ui/const-generics/generic_const_exprs/function-call.rs

@@ -1,3 +1,4 @@
+// compile-flags: -Zdeduplicate-diagnostics=yes
 // check-pass
 
 const fn foo<T>() -> usize {

src/test/ui/const-generics/generic_const_exprs/function-call.stderr

@@ -1,5 +1,5 @@
 warning: cannot use constants which depend on generic parameters in types
-  --> $DIR/function-call.rs:14:17
+  --> $DIR/function-call.rs:15:17
    |
 LL |     let _ = [0; foo::<T>()];
    |                 ^^^^^^^^^^

src/test/ui/const-generics/min_const_generics/const-evaluatable-unchecked.rs

@@ -1,3 +1,4 @@
+// compile-flags: -Zdeduplicate-diagnostics=yes
 // check-pass
 #![allow(dead_code)]
 

src/test/ui/const-generics/min_const_generics/const-evaluatable-unchecked.stderr

@@ -1,5 +1,5 @@
 warning: cannot use constants which depend on generic parameters in types
-  --> $DIR/const-evaluatable-unchecked.rs:5:9
+  --> $DIR/const-evaluatable-unchecked.rs:6:9
    |
 LL |     [0; std::mem::size_of::<*mut T>()];
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -9,7 +9,7 @@ LL |     [0; std::mem::size_of::<*mut T>()];
    = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
 
 warning: cannot use constants which depend on generic parameters in types
-  --> $DIR/const-evaluatable-unchecked.rs:16:21
+  --> $DIR/const-evaluatable-unchecked.rs:17:21
    |
 LL |         let _ = [0; Self::ASSOC];
    |                     ^^^^^^^^^^^
@@ -18,7 +18,7 @@ LL |         let _ = [0; Self::ASSOC];
    = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
 
 warning: cannot use constants which depend on generic parameters in types
-  --> $DIR/const-evaluatable-unchecked.rs:28:21
+  --> $DIR/const-evaluatable-unchecked.rs:29:21
    |
 LL |         let _ = [0; Self::ASSOC];
    |                     ^^^^^^^^^^^

src/test/ui/nll/closure-requirements/escape-argument-callee.stderr

@@ -17,7 +17,7 @@ LL |         let mut closure = expect_sig(|p, y| *p = y);
    |                                       -  -  ^^^^^^ assignment requires that `'1` must outlive `'2`
    |                                       |  |
    |                                       |  has type `&'1 i32`
-   |                                       has type `&'_#2r mut &'2 i32`
+   |                                       has type `&'2 mut &'_#3r i32`
 
 note: no external requirements
   --> $DIR/escape-argument-callee.rs:20:1

src/test/ui/nll/closure-requirements/escape-upvar-nested.stderr

@@ -10,6 +10,7 @@ LL |             let mut closure1 = || p = &y;
                (&'_#1r mut &'_#2r i32, &'_#3r i32),
            ]
    = note: number of external vids: 4
+   = note: where '_#3r: '_#1r
    = note: where '_#3r: '_#2r
 
 note: external requirements
@@ -28,6 +29,7 @@ LL | |         };
                (&'_#1r mut &'_#2r i32, &'_#3r i32),
            ]
    = note: number of external vids: 4
+   = note: where '_#3r: '_#1r
    = note: where '_#3r: '_#2r
 
 note: no external requirements

src/test/ui/nll/closure-requirements/escape-upvar-ref.stderr

@@ -10,6 +10,7 @@ LL |         let mut closure = || p = &y;
                (&'_#1r mut &'_#2r i32, &'_#3r i32),
            ]
    = note: number of external vids: 4
+   = note: where '_#3r: '_#1r
    = note: where '_#3r: '_#2r
 
 note: no external requirements

src/test/ui/nll/closure-requirements/propagate-approximated-ref.stderr

@@ -18,6 +18,8 @@ LL | |     });
    = note: late-bound region is '_#4r
    = note: number of external vids: 5
    = note: where '_#1r: '_#2r
+   = note: where '_#1r: '_#2r
+   = note: where '_#1r: '_#2r
 
 note: no external requirements
   --> $DIR/propagate-approximated-ref.rs:42:1

src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr

@@ -19,6 +19,7 @@ LL | |     });
    = note: late-bound region is '_#3r
    = note: number of external vids: 4
    = note: where '_#1r: '_#0r
+   = note: where '_#1r: '_#0r
 
 note: no external requirements
   --> $DIR/propagate-approximated-shorter-to-static-no-bound.rs:31:1

src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr

@@ -18,6 +18,9 @@ LL | |     });
    = note: late-bound region is '_#3r
    = note: late-bound region is '_#4r
    = note: number of external vids: 5
+   = note: where '_#1r: '_#2r
+   = note: where '_#1r: '_#2r
+   = note: where '_#1r: '_#0r
    = note: where '_#1r: '_#0r
 
 note: no external requirements

src/test/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-no-bounds.stderr

@@ -23,10 +23,14 @@ error: lifetime may not live long enough
 LL |     establish_relationships(&cell_a, &cell_b, |_outlives, x, y| {
    |                                                ---------  - has type `&'_#7r Cell<&'1 u32>`
    |                                                |
-   |                                                has type `&'_#5r Cell<&'2 &'_#1r u32>`
+   |                                                has type `&'2 Cell<&'_#6r &'_#1r u32>`
 LL |         // Only works if 'x: 'y:
 LL |         demand_y(x, y, x.get())
    |         ^^^^^^^^^^^^^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+   = note: requirement occurs because of the type `Cell<&'_#38r u32>`, which makes the generic argument `&'_#38r u32` invariant
+   = note: the struct `Cell<T>` is invariant over the parameter `T`
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 note: no external requirements
   --> $DIR/propagate-fail-to-approximate-longer-no-bounds.rs:34:1

src/test/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.rs

@@ -40,6 +40,7 @@ fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
         // Only works if 'x: 'y:
         demand_y(x, y, x.get())
         //~^ ERROR
+        //~| ERROR
     });
 }
 

src/test/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.stderr

@@ -1,11 +1,12 @@
-note: no external requirements
+note: external requirements
   --> $DIR/propagate-fail-to-approximate-longer-wrong-bounds.rs:39:47
    |
 LL |       establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
    |  _______________________________________________^
 LL | |         // Only works if 'x: 'y:
 LL | |         demand_y(x, y, x.get())
 LL | |
+LL | |
 LL | |     });
    | |_____^
    |
@@ -16,17 +17,25 @@ LL | |     });
            ]
    = note: late-bound region is '_#3r
    = note: late-bound region is '_#4r
+   = note: number of external vids: 5
+   = note: where '_#1r: '_#2r
+   = note: where '_#1r: '_#2r
+   = note: where '_#1r: '_#2r
 
 error: lifetime may not live long enough
   --> $DIR/propagate-fail-to-approximate-longer-wrong-bounds.rs:41:9
    |
 LL |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
-   |                                                ----------  ---------- has type `&'_#8r Cell<&'2 &'_#2r u32>`
+   |                                                ----------  ---------- has type `&'2 Cell<&'_#9r &'_#2r u32>`
    |                                                |
    |                                                has type `&'_#6r Cell<&'1 &'_#1r u32>`
 LL |         // Only works if 'x: 'y:
 LL |         demand_y(x, y, x.get())
    |         ^^^^^^^^^^^^^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+   = note: requirement occurs because of the type `Cell<&'_#44r u32>`, which makes the generic argument `&'_#44r u32` invariant
+   = note: the struct `Cell<T>` is invariant over the parameter `T`
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 note: no external requirements
   --> $DIR/propagate-fail-to-approximate-longer-wrong-bounds.rs:38:1
@@ -35,12 +44,25 @@ LL | / fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
 LL | |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
 LL | |         // Only works if 'x: 'y:
 LL | |         demand_y(x, y, x.get())
-LL | |
+...  |
 LL | |     });
 LL | | }
    | |_^
    |
    = note: defining type: supply
 
-error: aborting due to previous error
+error: lifetime may not live long enough
+  --> $DIR/propagate-fail-to-approximate-longer-wrong-bounds.rs:41:9
+   |
+LL | fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
+   |           --  -- lifetime `'b` defined here
+   |           |
+   |           lifetime `'a` defined here
+...
+LL |         demand_y(x, y, x.get())
+   |         ^^^^^^^^^^^^^^^^^^^^^^^ argument requires that `'a` must outlive `'b`
+   |
+   = help: consider adding the following bound: `'a: 'b`
+
+error: aborting due to 2 previous errors
 

src/test/ui/nll/issue-95272.rs

@@ -10,8 +10,7 @@ where
 
 fn test<'a, 'b>(x: Cell<&'a ()>, y: Cell<&'b ()>) {
     let f = check;
-    //~^ ERROR lifetime may not live long enough
-    f(x, y);
+    f(x, y); //~ ERROR lifetime may not live long enough
 }
 
 fn main() {}

src/test/ui/nll/issue-95272.stderr

@@ -1,16 +1,17 @@
 error: lifetime may not live long enough
-  --> $DIR/issue-95272.rs:12:13
+  --> $DIR/issue-95272.rs:13:5
    |
 LL | fn test<'a, 'b>(x: Cell<&'a ()>, y: Cell<&'b ()>) {
    |         --  -- lifetime `'b` defined here
    |         |
    |         lifetime `'a` defined here
 LL |     let f = check;
-   |             ^^^^^ assignment requires that `'a` must outlive `'b`
+LL |     f(x, y);
+   |     ^^^^^^^ argument requires that `'a` must outlive `'b`
    |
    = help: consider adding the following bound: `'a: 'b`
-   = note: requirement occurs because of a function pointer to `check`
-   = note: the function `check` is invariant over the parameter `'a`
+   = note: requirement occurs because of the type `Cell<&()>`, which makes the generic argument `&()` invariant
+   = note: the struct `Cell<T>` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: aborting due to previous error

src/test/ui/nll/type-check-pointer-coercions.stderr

@@ -22,21 +22,14 @@ LL |     x
    |
    = help: consider adding the following bound: `'a: 'b`
 
-error: lifetime may not live long enough
+error[E0621]: explicit lifetime required in the type of `x`
   --> $DIR/type-check-pointer-coercions.rs:13:5
    |
 LL | fn unique_to_mut<'a, 'b>(x: &mut &'a i32) -> *mut &'b i32 {
-   |                  --  -- lifetime `'b` defined here
-   |                  |
-   |                  lifetime `'a` defined here
+   |                             ------------ help: add explicit lifetime `'b` to the type of `x`: `&'b mut &'a i32`
 LL |     // Two errors because *mut is invariant
 LL |     x
-   |     ^ function was supposed to return data with lifetime `'a` but it is returning data with lifetime `'b`
-   |
-   = help: consider adding the following bound: `'b: 'a`
-   = note: requirement occurs because of a mutable pointer to `&i32`
-   = note: mutable pointers are invariant over their type parameter
-   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
+   |     ^ lifetime `'b` required
 
 error: lifetime may not live long enough
   --> $DIR/type-check-pointer-coercions.rs:13:5
@@ -54,8 +47,6 @@ LL |     x
    = note: mutable pointers are invariant over their type parameter
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
-help: `'b` and `'a` must be the same: replace one with the other
-
 error: lifetime may not live long enough
   --> $DIR/type-check-pointer-coercions.rs:18:5
    |
@@ -109,3 +100,4 @@ LL |     y
 
 error: aborting due to 8 previous errors
 
+For more information about this error, try `rustc --explain E0621`.

src/test/ui/nll/type-check-pointer-comparisons.rs

@@ -4,7 +4,7 @@
 
 fn compare_const<'a, 'b>(x: *const &mut &'a i32, y: *const &mut &'b i32) {
     x == y;
-    //~^ ERROR lifetime may not live long enough
+    //~^ ERROR explicit lifetime required in the type of `y`
     //~| ERROR lifetime may not live long enough
 }
 

src/test/ui/nll/type-check-pointer-comparisons.stderr

@@ -1,17 +1,10 @@
-error: lifetime may not live long enough
+error[E0621]: explicit lifetime required in the type of `y`
   --> $DIR/type-check-pointer-comparisons.rs:6:5
    |
 LL | fn compare_const<'a, 'b>(x: *const &mut &'a i32, y: *const &mut &'b i32) {
-   |                  --  -- lifetime `'b` defined here
-   |                  |
-   |                  lifetime `'a` defined here
+   |                                                     ------------------- help: add explicit lifetime `'a` to the type of `y`: `*const &'a mut &'b i32`
 LL |     x == y;
-   |     ^ requires that `'a` must outlive `'b`
-   |
-   = help: consider adding the following bound: `'a: 'b`
-   = note: requirement occurs because of a mutable reference to `&i32`
-   = note: mutable references are invariant over their type parameter
-   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
+   |     ^ lifetime `'a` required
 
 error: lifetime may not live long enough
   --> $DIR/type-check-pointer-comparisons.rs:6:10
@@ -28,8 +21,6 @@ LL |     x == y;
    = note: mutable references are invariant over their type parameter
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
-help: `'a` and `'b` must be the same: replace one with the other
-
 error: lifetime may not live long enough
   --> $DIR/type-check-pointer-comparisons.rs:12:5
    |
@@ -96,3 +87,4 @@ help: `'a` and `'b` must be the same: replace one with the other
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0621`.

src/test/ui/unboxed-closures/unboxed-closures-infer-argument-types-two-region-pointers.nll.stderr

@@ -4,9 +4,13 @@ error: lifetime may not live long enough
 LL |     doit(0, &|x, y| {
    |               -  - has type `&'1 i32`
    |               |
-   |               has type `&Cell<&'2 i32>`
+   |               has type `&'2 Cell<&i32>`
 LL |         x.set(y);
    |         ^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+   = note: requirement occurs because of the type `Cell<&i32>`, which makes the generic argument `&i32` invariant
+   = note: the struct `Cell<T>` is invariant over the parameter `T`
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: aborting due to previous error
 

src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.nll.stderr

@@ -2,10 +2,14 @@ error: lifetime may not live long enough
   --> $DIR/underscore-lifetime-elison-mismatch.rs:5:42
    |
 LL | fn foo(x: &mut Vec<&'_ u8>, y: &'_ u8) { x.push(y); }
-   |                    -           -         ^^^^^^^^^ argument requires that `'1` must outlive `'2`
-   |                    |           |
-   |                    |           let's call the lifetime of this reference `'1`
-   |                    let's call the lifetime of this reference `'2`
+   |           -                    -         ^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |           |                    |
+   |           |                    let's call the lifetime of this reference `'1`
+   |           let's call the lifetime of this reference `'2`
+   |
+   = note: requirement occurs because of a mutable reference to `Vec<&u8>`
+   = note: mutable references are invariant over their type parameter
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: aborting due to previous error