Auto merge of #55937 - davidtwco:issue-54943, r=pnkfelix

NLL: User type annotations refactor, associated constant patterns and ref bindings.

Fixes #55511 and Fixes #55401. Contributes to #54943.

This PR performs a large refactoring on user type annotations, checks user type annotations for associated constants in patterns and that user type annotations for `ref` bindings are respected.

r? @nikomatsakis

16 files changed, 150 insertions, 14 deletions

diff --git a/src/test/incremental/hashes/let_expressions.rs b/src/test/incremental/hashes/let_expressions.rs
index 3aa66527ca7..b6050f059c2 100644
--- a/src/test/incremental/hashes/let_expressions.rs
+++ b/src/test/incremental/hashes/let_expressions.rs
@@ -70,7 +70,7 @@ pub fn change_mutability_of_reference_type() {
 
 #[cfg(not(cfail1))]
 #[rustc_clean(cfg="cfail2",
-    except="HirBody,TypeckTables,MirValidated")]
+    except="HirBody,TypeckTables,MirValidated,MirOptimized")]
 #[rustc_clean(cfg="cfail3")]
 pub fn change_mutability_of_reference_type() {
     let _x: &mut u64;
diff --git a/src/test/mir-opt/basic_assignment.rs b/src/test/mir-opt/basic_assignment.rs
index bb304ea12ca..88fd53d4ba5 100644
--- a/src/test/mir-opt/basic_assignment.rs
+++ b/src/test/mir-opt/basic_assignment.rs
@@ -37,7 +37,7 @@ fn main() {
 //        StorageLive(_4);
 //        _4 = std::option::Option<std::boxed::Box<u32>>::None;
 //        FakeRead(ForLet, _4);
-//        AscribeUserType(_4, o, UserTypeProjection { base: Ty(Canonical { max_universe: U0, variables: [], value: std::option::Option<std::boxed::Box<u32>> }), projs: [] });
+//        AscribeUserType(_4, o, UserTypeProjection { base: UserTypeAnnotation(1), projs: [] });
 //        StorageLive(_5);
 //        StorageLive(_6);
 //        _6 = move _4;
diff --git a/src/test/run-pass/associated-consts/associated-const-range-match-patterns.rs b/src/test/run-pass/associated-consts/associated-const-range-match-patterns.rs
index 647652d0273..4801369cfd1 100644
--- a/src/test/run-pass/associated-consts/associated-const-range-match-patterns.rs
+++ b/src/test/run-pass/associated-consts/associated-const-range-match-patterns.rs
@@ -1,5 +1,5 @@
 // run-pass
-#![allow(dead_code)]
+#![allow(dead_code, unreachable_patterns)]
 
 struct Foo;
 
diff --git a/src/test/ui/issue-54943-1.rs b/src/test/ui/issue-54943-1.rs
new file mode 100644
index 00000000000..7750e340361
--- /dev/null
+++ b/src/test/ui/issue-54943-1.rs
@@ -0,0 +1,15 @@
+#![feature(nll)]
+
+// This test is a minimal version of an ICE in the dropck-eyepatch tests
+// found in the fix for #54943.
+
+// compile-pass
+
+fn foo<T>(_t: T) {
+}
+
+fn main() {
+    struct A<'a, B: 'a>(&'a B);
+    let (a1, a2): (String, A<_>) = (String::from("auto"), A(&"this"));
+    foo((a1, a2));
+}
diff --git a/src/test/ui/issue-54943-2.rs b/src/test/ui/issue-54943-2.rs
new file mode 100644
index 00000000000..f829c38c35d
--- /dev/null
+++ b/src/test/ui/issue-54943-2.rs
@@ -0,0 +1,18 @@
+#![feature(nll)]
+
+// This test is a minimal version of an ICE in the dropck-eyepatch tests
+// found in the fix for #54943. In particular, this test is in unreachable
+// code as the initial fix for this ICE only worked if the code was reachable.
+
+// compile-pass
+
+fn foo<T>(_t: T) {
+}
+
+fn main() {
+    return;
+
+    struct A<'a, B: 'a>(&'a B);
+    let (a1, a2): (String, A<_>) = (String::from("auto"), A(&"this"));
+    foo((a1, a2));
+}
diff --git a/src/test/ui/issue-54943-3.rs b/src/test/ui/issue-54943-3.rs
new file mode 100644
index 00000000000..185077bd684
--- /dev/null
+++ b/src/test/ui/issue-54943-3.rs
@@ -0,0 +1,21 @@
+// compile-pass
+// FIXME(#54943) This test targets the scenario where proving the WF requirements requires
+// knowing the value of the `_` type present in the user type annotation - unfortunately, figuring
+// out the value of that `_` requires type-checking the surrounding code, but that code is dead,
+// so our NLL region checker doesn't have access to it. This test should actually fail to compile.
+
+#![feature(nll)]
+#![allow(warnings)]
+
+use std::fmt::Debug;
+
+fn foo<T: 'static + Debug>(_: T) { }
+
+fn bar<'a>() {
+    return;
+
+    let _x = foo::<Vec<_>>(Vec::<&'a u32>::new());
+    //~^ ERROR the type `&'a u32` does not fulfill the required lifetime [E0477]
+}
+
+fn main() {}
diff --git a/src/test/ui/issue-54943.rs b/src/test/ui/issue-54943.rs
new file mode 100644
index 00000000000..c720f627975
--- /dev/null
+++ b/src/test/ui/issue-54943.rs
@@ -0,0 +1,17 @@
+// compile-pass
+// FIXME(#54943) This test targets the scenario where proving the WF requirements of a user
+// type annotation requires checking dead code. This test should actually fail to compile.
+
+#![feature(nll)]
+#![allow(warnings)]
+
+fn foo<T: 'static>() { }
+
+fn boo<'a>() {
+    return;
+
+    let x = foo::<&'a u32>();
+    //~^ ERROR the type `&'a u32` does not fulfill the required lifetime [E0477]
+}
+
+fn main() {}
diff --git a/src/test/ui/issue-55511.nll.stderr b/src/test/ui/issue-55511.nll.stderr
new file mode 100644
index 00000000000..bf3e58e8cdb
--- /dev/null
+++ b/src/test/ui/issue-55511.nll.stderr
@@ -0,0 +1,15 @@
+error[E0597]: `a` does not live long enough
+  --> $DIR/issue-55511.rs:13:28
+   |
+LL |     let b = Some(Cell::new(&a));
+   |                            ^^ borrowed value does not live long enough
+...
+LL |         <() as Foo<'static>>::C => { }
+   |         ----------------------- type annotation requires that `a` is borrowed for `'static`
+...
+LL | }
+   | - `a` dropped here while still borrowed
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.
diff --git a/src/test/ui/issue-55511.rs b/src/test/ui/issue-55511.rs
new file mode 100644
index 00000000000..4b9475ba627
--- /dev/null
+++ b/src/test/ui/issue-55511.rs
@@ -0,0 +1,19 @@
+use std::cell::Cell;
+
+trait Foo<'a> {
+    const C: Option<Cell<&'a u32>>;
+}
+
+impl<'a, T> Foo<'a> for T {
+    const C: Option<Cell<&'a u32>> = None;
+}
+
+fn main() {
+    let a = 22;
+    let b = Some(Cell::new(&a));
+    //~^ ERROR `a` does not live long enough [E0597]
+    match b {
+        <() as Foo<'static>>::C => { }
+        _ => { }
+    }
+}
diff --git a/src/test/ui/issue-55511.stderr b/src/test/ui/issue-55511.stderr
new file mode 100644
index 00000000000..24668f04551
--- /dev/null
+++ b/src/test/ui/issue-55511.stderr
@@ -0,0 +1,14 @@
+error[E0597]: `a` does not live long enough
+  --> $DIR/issue-55511.rs:13:29
+   |
+LL |     let b = Some(Cell::new(&a));
+   |                             ^ borrowed value does not live long enough
+...
+LL | }
+   | - borrowed value only lives until here
+   |
+   = note: borrowed value must be valid for the static lifetime...
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.
diff --git a/src/test/ui/nll/issue-55401.rs b/src/test/ui/nll/issue-55401.rs
new file mode 100644
index 00000000000..2fa23449108
--- /dev/null
+++ b/src/test/ui/nll/issue-55401.rs
@@ -0,0 +1,8 @@
+#![feature(nll)]
+
+fn static_to_a_to_static_through_ref_in_tuple<'a>(x: &'a u32) -> &'static u32 {
+    let (ref y, _z): (&'a u32, u32) = (&22, 44);
+    *y //~ ERROR
+}
+
+fn main() {}
diff --git a/src/test/ui/nll/issue-55401.stderr b/src/test/ui/nll/issue-55401.stderr
new file mode 100644
index 00000000000..9e50db7b604
--- /dev/null
+++ b/src/test/ui/nll/issue-55401.stderr
@@ -0,0 +1,11 @@
+error: unsatisfied lifetime constraints
+  --> $DIR/issue-55401.rs:5:5
+   |
+LL | fn static_to_a_to_static_through_ref_in_tuple<'a>(x: &'a u32) -> &'static u32 {
+   |                                               -- lifetime `'a` defined here
+LL |     let (ref y, _z): (&'a u32, u32) = (&22, 44);
+LL |     *y //~ ERROR
+   |     ^^ returning this value requires that `'a` must outlive `'static`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/nll/user-annotations/dump-adt-brace-struct.stderr b/src/test/ui/nll/user-annotations/dump-adt-brace-struct.stderr
index 5a359cf9ed8..123c26195d0 100644
--- a/src/test/ui/nll/user-annotations/dump-adt-brace-struct.stderr
+++ b/src/test/ui/nll/user-annotations/dump-adt-brace-struct.stderr
@@ -1,4 +1,4 @@
-error: user substs: Canonical { max_universe: U0, variables: [], value: UserSubsts { substs: [u32], user_self_ty: None } }
+error: user substs: UserSubsts { substs: [u32], user_self_ty: None }
   --> $DIR/dump-adt-brace-struct.rs:18:5
    |
 LL |     SomeStruct::<u32> { t: 22 }; //~ ERROR [u32]
diff --git a/src/test/ui/nll/user-annotations/dump-fn-method.stderr b/src/test/ui/nll/user-annotations/dump-fn-method.stderr
index 3f159cc92b5..a1a4e43e8a3 100644
--- a/src/test/ui/nll/user-annotations/dump-fn-method.stderr
+++ b/src/test/ui/nll/user-annotations/dump-fn-method.stderr
@@ -1,22 +1,22 @@
-error: user substs: Canonical { max_universe: U0, variables: [], value: UserSubsts { substs: [u32], user_self_ty: None } }
+error: user substs: UserSubsts { substs: [u32], user_self_ty: None }
   --> $DIR/dump-fn-method.rs:26:13
    |
 LL |     let x = foo::<u32>; //~ ERROR [u32]
    |             ^^^^^^^^^^
 
-error: user substs: Canonical { max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }, CanonicalVarInfo { kind: Ty(General(U0)) }], value: UserSubsts { substs: [^0, u32, ^1], user_self_ty: None } }
+error: user substs: UserSubsts { substs: [^0, u32, ^1], user_self_ty: None }
   --> $DIR/dump-fn-method.rs:32:13
    |
 LL |     let x = <_ as Bazoom<u32>>::method::<_>; //~ ERROR [^0, u32, ^1]
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: user substs: Canonical { max_universe: U0, variables: [], value: UserSubsts { substs: [u8, u16, u32], user_self_ty: None } }
+error: user substs: UserSubsts { substs: [u8, u16, u32], user_self_ty: None }
   --> $DIR/dump-fn-method.rs:36:13
    |
 LL |     let x = <u8 as Bazoom<u16>>::method::<u32>; //~ ERROR [u8, u16, u32]
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: user substs: Canonical { max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }, CanonicalVarInfo { kind: Ty(General(U0)) }], value: UserSubsts { substs: [^0, ^1, u32], user_self_ty: None } }
+error: user substs: UserSubsts { substs: [^0, ^1, u32], user_self_ty: None }
   --> $DIR/dump-fn-method.rs:44:5
    |
 LL |     y.method::<u32>(44, 66); //~ ERROR [^0, ^1, u32]
diff --git a/src/test/ui/regions/regions-outlives-projection-container-wc.rs b/src/test/ui/regions/regions-outlives-projection-container-wc.rs
index d38706defe7..91a0d8590ff 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-wc.rs
+++ b/src/test/ui/regions/regions-outlives-projection-container-wc.rs
@@ -31,9 +31,7 @@ fn with_assoc<'a,'b>() {
     // outlive 'a. In this case, that means TheType<'b>::TheAssocType,
     // which is &'b (), must outlive 'a.
 
-    // FIXME (#54943) NLL doesn't enforce WF condition in unreachable code if
-    // `_x` is changed to `_`
-    let _x: &'a WithAssoc<TheType<'b>> = loop { };
+    let _: &'a WithAssoc<TheType<'b>> = loop { };
     //~^ ERROR reference has a longer lifetime
 }
 
diff --git a/src/test/ui/regions/regions-outlives-projection-container-wc.stderr b/src/test/ui/regions/regions-outlives-projection-container-wc.stderr
index 2ed9fd4f9b4..0d73d3d6432 100644
--- a/src/test/ui/regions/regions-outlives-projection-container-wc.stderr
+++ b/src/test/ui/regions/regions-outlives-projection-container-wc.stderr
@@ -1,8 +1,8 @@
 error[E0491]: in type `&'a WithAssoc<TheType<'b>>`, reference has a longer lifetime than the data it references
-  --> $DIR/regions-outlives-projection-container-wc.rs:36:13
+  --> $DIR/regions-outlives-projection-container-wc.rs:34:12
    |
-LL |     let _x: &'a WithAssoc<TheType<'b>> = loop { };
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _: &'a WithAssoc<TheType<'b>> = loop { };
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 note: the pointer is valid for the lifetime 'a as defined on the function body at 28:15
   --> $DIR/regions-outlives-projection-container-wc.rs:28:15