Auto merge of #88329 - LeSeulArtichaut:rollup-blg8hc0, r=LeSeulArtichaut

Rollup of 16 pull requests

Successful merges:

 - #87944 (add Cell::as_array_of_cells, similar to Cell::as_slice_of_cells)
 - #88156 (Adjust / fix documentation of `Arc::make_mut`)
 - #88157 (bootstrap.py: recognize riscv64 when auto-detect)
 - #88196 (Refactor `named_asm_labels` to a HIR lint)
 - #88218 (Remove `Session.trait_methods_not_found`)
 - #88223 (Remove the `TryV2` alias)
 - #88226 (Fix typo “a Rc” → “an Rc” (and a few more))
 - #88267 (2229: Update signature for truncate function)
 - #88273 (Fix references to `ControlFlow` in docs)
 - #88277 (Update books)
 - #88291 (Add SAFETY comments to core::slice::sort::partition_in_blocks)
 - #88293 (Fix grammar in alloc test)
 - #88298 (Errorkind reorder)
 - #88299 (Stabilise BufWriter::into_parts)
 - #88314 (Add type of a let tait test)
 - #88325 (Add mutable-noalias to the release notes for 1.54)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

13 files changed, 312 insertions, 33 deletions

diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 3faf38c66ec..e34768bc2c9 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -301,6 +301,7 @@ def default_build_triple(verbose):
         'ppc': 'powerpc',
         'ppc64': 'powerpc64',
         'ppc64le': 'powerpc64le',
+        'riscv64': 'riscv64gc',
         's390x': 's390x',
         'x64': 'x86_64',
         'x86': 'i686',
diff --git a/src/doc/book b/src/doc/book
-Subproject 7e49659102f0977d9142190e1ba23345c0f00eb
+Subproject 687e21bde2ea10c261f79fa14797c5137425098
diff --git a/src/doc/reference b/src/doc/reference
-Subproject 4884fe45c14f8b22121760fb117181bb4da8dfe
+Subproject da6ea9b03f74cae0a292f40315723d7a3a97363
diff --git a/src/doc/rust-by-example b/src/doc/rust-by-example
-Subproject 0dc9cd4e89f00cb5230f120e1a083916386e422
+Subproject 04f489c889235fe3b6dfe678ae5410d07deda95
diff --git a/src/doc/rustc-dev-guide b/src/doc/rustc-dev-guide
-Subproject c4644b427cbdaafc7a87be0ccdf5d8aaa07ac35
+Subproject cf0e151b7925a40f13fbc6573c6f97d5f94c7c1
diff --git a/src/test/ui/asm/named-asm-labels.rs b/src/test/ui/asm/named-asm-labels.rs
index 803501b40b6..9f487bd8061 100644
--- a/src/test/ui/asm/named-asm-labels.rs
+++ b/src/test/ui/asm/named-asm-labels.rs
@@ -1,6 +1,14 @@
 // only-x86_64
 
-#![feature(asm, global_asm)]
+// Tests that the use of named labels in the `asm!` macro are linted against
+// except for in `#[naked]` fns.
+// Using a named label is incorrect as per the RFC because for most cases
+// the compiler cannot ensure that inline asm is emitted exactly once per
+// codegen unit (except for naked fns) and so the label could be duplicated
+// which causes less readable LLVM errors and in the worst cases causes ICEs
+// or segfaults based on system dependent behavior and codegen flags.
+
+#![feature(asm, global_asm, naked_functions)]
 
 #[no_mangle]
 pub static FOO: usize = 42;
@@ -126,5 +134,61 @@ fn main() {
     }
 }
 
+// Trigger on naked fns too, even though they can't be inlined, reusing a
+// label or LTO can cause labels to break
+#[naked]
+pub extern "C" fn foo() -> i32 {
+    unsafe { asm!(".Lfoo: mov rax, {}; ret;", "nop", const 1, options(noreturn)) } //~ ERROR avoid using named labels
+}
+
+// Make sure that non-naked attributes *do* still let the lint happen
+#[no_mangle]
+pub extern "C" fn bar() {
+    unsafe { asm!(".Lbar: mov rax, {}; ret;", "nop", const 1, options(noreturn)) }
+    //~^ ERROR avoid using named labels
+}
+
+#[naked]
+pub extern "C" fn aaa() {
+    fn _local() {}
+
+    unsafe { asm!(".Laaa: nop; ret;", options(noreturn)) } //~ ERROR avoid using named labels
+}
+
+pub fn normal() {
+    fn _local1() {}
+
+    #[naked]
+    pub extern "C" fn bbb() {
+        fn _very_local() {}
+
+        unsafe { asm!(".Lbbb: nop; ret;", options(noreturn)) } //~ ERROR avoid using named labels
+    }
+
+    fn _local2() {}
+}
+
+// Make sure that the lint happens within closures
+fn closures() {
+    || unsafe {
+        asm!("closure1: nop"); //~ ERROR avoid using named labels
+    };
+
+    move || unsafe {
+        asm!("closure2: nop"); //~ ERROR avoid using named labels
+    };
+
+    || {
+        #[naked]
+        unsafe extern "C" fn _nested() {
+            asm!("ret;", options(noreturn));
+        }
+
+        unsafe {
+            asm!("closure3: nop"); //~ ERROR avoid using named labels
+        }
+    };
+}
+
 // Don't trigger on global asm
 global_asm!("aaaaaaaa: nop");
diff --git a/src/test/ui/asm/named-asm-labels.stderr b/src/test/ui/asm/named-asm-labels.stderr
index 3c4a4db75e0..396f0a19424 100644
--- a/src/test/ui/asm/named-asm-labels.stderr
+++ b/src/test/ui/asm/named-asm-labels.stderr
@@ -1,5 +1,5 @@
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:11:15
+  --> $DIR/named-asm-labels.rs:19:15
    |
 LL |         asm!("bar: nop");
    |               ^^^
@@ -9,7 +9,7 @@ LL |         asm!("bar: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:14:15
+  --> $DIR/named-asm-labels.rs:22:15
    |
 LL |         asm!("abcd:");
    |               ^^^^
@@ -18,7 +18,7 @@ LL |         asm!("abcd:");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:17:15
+  --> $DIR/named-asm-labels.rs:25:15
    |
 LL |         asm!("foo: bar1: nop");
    |               ^^^  ^^^^
@@ -27,7 +27,7 @@ LL |         asm!("foo: bar1: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:21:15
+  --> $DIR/named-asm-labels.rs:29:15
    |
 LL |         asm!("foo1: nop", "nop");
    |               ^^^^
@@ -36,7 +36,7 @@ LL |         asm!("foo1: nop", "nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:22:15
+  --> $DIR/named-asm-labels.rs:30:15
    |
 LL |         asm!("foo2: foo3: nop", "nop");
    |               ^^^^  ^^^^
@@ -45,7 +45,7 @@ LL |         asm!("foo2: foo3: nop", "nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:24:22
+  --> $DIR/named-asm-labels.rs:32:22
    |
 LL |         asm!("nop", "foo4: nop");
    |                      ^^^^
@@ -54,7 +54,7 @@ LL |         asm!("nop", "foo4: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:25:15
+  --> $DIR/named-asm-labels.rs:33:15
    |
 LL |         asm!("foo5: nop", "foo6: nop");
    |               ^^^^
@@ -63,7 +63,7 @@ LL |         asm!("foo5: nop", "foo6: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:25:28
+  --> $DIR/named-asm-labels.rs:33:28
    |
 LL |         asm!("foo5: nop", "foo6: nop");
    |                            ^^^^
@@ -72,7 +72,7 @@ LL |         asm!("foo5: nop", "foo6: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:30:15
+  --> $DIR/named-asm-labels.rs:38:15
    |
 LL |         asm!("foo7: nop; foo8: nop");
    |               ^^^^       ^^^^
@@ -81,7 +81,7 @@ LL |         asm!("foo7: nop; foo8: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:32:15
+  --> $DIR/named-asm-labels.rs:40:15
    |
 LL |         asm!("foo9: nop; nop");
    |               ^^^^
@@ -90,7 +90,7 @@ LL |         asm!("foo9: nop; nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:33:20
+  --> $DIR/named-asm-labels.rs:41:20
    |
 LL |         asm!("nop; foo10: nop");
    |                    ^^^^^
@@ -99,7 +99,7 @@ LL |         asm!("nop; foo10: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:36:15
+  --> $DIR/named-asm-labels.rs:44:15
    |
 LL |         asm!("bar2: nop\n bar3: nop");
    |               ^^^^        ^^^^
@@ -108,7 +108,7 @@ LL |         asm!("bar2: nop\n bar3: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:38:15
+  --> $DIR/named-asm-labels.rs:46:15
    |
 LL |         asm!("bar4: nop\n nop");
    |               ^^^^
@@ -117,7 +117,7 @@ LL |         asm!("bar4: nop\n nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:39:21
+  --> $DIR/named-asm-labels.rs:47:21
    |
 LL |         asm!("nop\n bar5: nop");
    |                     ^^^^
@@ -126,7 +126,7 @@ LL |         asm!("nop\n bar5: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:40:21
+  --> $DIR/named-asm-labels.rs:48:21
    |
 LL |         asm!("nop\n bar6: bar7: nop");
    |                     ^^^^  ^^^^
@@ -135,7 +135,7 @@ LL |         asm!("nop\n bar6: bar7: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:46:13
+  --> $DIR/named-asm-labels.rs:54:13
    |
 LL |             blah2: nop
    |             ^^^^^
@@ -146,7 +146,7 @@ LL |             blah3: nop
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:55:19
+  --> $DIR/named-asm-labels.rs:63:19
    |
 LL |             nop ; blah4: nop
    |                   ^^^^^
@@ -155,7 +155,7 @@ LL |             nop ; blah4: nop
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:69:15
+  --> $DIR/named-asm-labels.rs:77:15
    |
 LL |         asm!("blah1: 2bar: nop");
    |               ^^^^^
@@ -164,7 +164,7 @@ LL |         asm!("blah1: 2bar: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:72:15
+  --> $DIR/named-asm-labels.rs:80:15
    |
 LL |         asm!("def: def: nop");
    |               ^^^
@@ -173,7 +173,7 @@ LL |         asm!("def: def: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:73:15
+  --> $DIR/named-asm-labels.rs:81:15
    |
 LL |         asm!("def: nop\ndef: nop");
    |               ^^^
@@ -182,7 +182,7 @@ LL |         asm!("def: nop\ndef: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:74:15
+  --> $DIR/named-asm-labels.rs:82:15
    |
 LL |         asm!("def: nop; def: nop");
    |               ^^^
@@ -191,7 +191,7 @@ LL |         asm!("def: nop; def: nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:82:15
+  --> $DIR/named-asm-labels.rs:90:15
    |
 LL |         asm!("fooo\u{003A} nop");
    |               ^^^^^^^^^^^^^^^^
@@ -200,7 +200,7 @@ LL |         asm!("fooo\u{003A} nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:83:15
+  --> $DIR/named-asm-labels.rs:91:15
    |
 LL |         asm!("foooo\x3A nop");
    |               ^^^^^^^^^^^^^
@@ -209,7 +209,7 @@ LL |         asm!("foooo\x3A nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:86:15
+  --> $DIR/named-asm-labels.rs:94:15
    |
 LL |         asm!("fooooo:\u{000A} nop");
    |               ^^^^^^
@@ -218,7 +218,7 @@ LL |         asm!("fooooo:\u{000A} nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:87:15
+  --> $DIR/named-asm-labels.rs:95:15
    |
 LL |         asm!("foooooo:\x0A nop");
    |               ^^^^^^^
@@ -227,7 +227,7 @@ LL |         asm!("foooooo:\x0A nop");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:91:14
+  --> $DIR/named-asm-labels.rs:99:14
    |
 LL |         asm!("\x41\x42\x43\x3A\x20\x6E\x6F\x70");
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -236,7 +236,7 @@ LL |         asm!("\x41\x42\x43\x3A\x20\x6E\x6F\x70");
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:102:13
+  --> $DIR/named-asm-labels.rs:110:13
    |
 LL |             ab: nop // ab: does foo
    |             ^^
@@ -245,7 +245,7 @@ LL |             ab: nop // ab: does foo
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 error: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:114:14
+  --> $DIR/named-asm-labels.rs:122:14
    |
 LL |         asm!(include_str!("named-asm-labels.s"));
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -254,18 +254,81 @@ LL |         asm!(include_str!("named-asm-labels.s"));
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
 warning: avoid using named labels in inline assembly
-  --> $DIR/named-asm-labels.rs:124:19
+  --> $DIR/named-asm-labels.rs:132:19
    |
 LL |             asm!("warned: nop");
    |                   ^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/named-asm-labels.rs:122:16
+  --> $DIR/named-asm-labels.rs:130:16
    |
 LL |         #[warn(named_asm_labels)]
    |                ^^^^^^^^^^^^^^^^
    = help: only local labels of the form `<number>:` should be used in inline asm
    = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
 
-error: aborting due to 28 previous errors; 1 warning emitted
+error: avoid using named labels in inline assembly
+  --> $DIR/named-asm-labels.rs:141:20
+   |
+LL |     unsafe { asm!(".Lfoo: mov rax, {}; ret;", "nop", const 1, options(noreturn)) }
+   |                    ^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
+
+error: avoid using named labels in inline assembly
+  --> $DIR/named-asm-labels.rs:147:20
+   |
+LL |     unsafe { asm!(".Lbar: mov rax, {}; ret;", "nop", const 1, options(noreturn)) }
+   |                    ^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
+
+error: avoid using named labels in inline assembly
+  --> $DIR/named-asm-labels.rs:155:20
+   |
+LL |     unsafe { asm!(".Laaa: nop; ret;", options(noreturn)) }
+   |                    ^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
+
+error: avoid using named labels in inline assembly
+  --> $DIR/named-asm-labels.rs:165:24
+   |
+LL |         unsafe { asm!(".Lbbb: nop; ret;", options(noreturn)) }
+   |                        ^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
+
+error: avoid using named labels in inline assembly
+  --> $DIR/named-asm-labels.rs:174:15
+   |
+LL |         asm!("closure1: nop");
+   |               ^^^^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
+
+error: avoid using named labels in inline assembly
+  --> $DIR/named-asm-labels.rs:178:15
+   |
+LL |         asm!("closure2: nop");
+   |               ^^^^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
+
+error: avoid using named labels in inline assembly
+  --> $DIR/named-asm-labels.rs:188:19
+   |
+LL |             asm!("closure3: nop");
+   |                   ^^^^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information
+
+error: aborting due to 35 previous errors; 1 warning emitted
 
diff --git a/src/test/ui/drop/dropck_legal_cycles.rs b/src/test/ui/drop/dropck_legal_cycles.rs
index fb13fd764bf..27a599315dc 100644
--- a/src/test/ui/drop/dropck_legal_cycles.rs
+++ b/src/test/ui/drop/dropck_legal_cycles.rs
@@ -368,7 +368,7 @@ pub fn main() {
     // We can use refcells if we're single-threaded (as this test is).
     // If one were to generalize these constructions to a
     // multi-threaded context, then it might seem like we could choose
-    // between either a RwLock or a Mutex to hold the owned arcs on
+    // between either an RwLock or a Mutex to hold the owned arcs on
     // each node.
     //
     // Part of the point of this test is to actually confirm that the
diff --git a/src/test/ui/rfcs/rfc-1789-as-cell/from-mut.rs b/src/test/ui/rfcs/rfc-1789-as-cell/from-mut.rs
index ea3ad7aed49..329fadb150f 100644
--- a/src/test/ui/rfcs/rfc-1789-as-cell/from-mut.rs
+++ b/src/test/ui/rfcs/rfc-1789-as-cell/from-mut.rs
@@ -1,5 +1,7 @@
 // run-pass
 
+#![feature(as_array_of_cells)]
+
 use std::cell::Cell;
 
 fn main() {
@@ -8,4 +10,11 @@ fn main() {
     let slice_cell: &[Cell<i32>] = cell_slice.as_slice_of_cells();
 
     assert_eq!(slice_cell.len(), 3);
+
+    let mut array: [i32; 3] = [1, 2, 3];
+    let cell_array: &Cell<[i32; 3]> = Cell::from_mut(&mut array);
+    let array_cell: &[Cell<i32>; 3] = cell_array.as_array_of_cells();
+
+    array_cell[0].set(99);
+    assert_eq!(array, [99, 2, 3]);
 }
diff --git a/src/test/ui/type-alias-impl-trait/type_of_a_let.rs b/src/test/ui/type-alias-impl-trait/type_of_a_let.rs
new file mode 100644
index 00000000000..7f8e6127cca
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/type_of_a_let.rs
@@ -0,0 +1,29 @@
+#![feature(type_alias_impl_trait)]
+#![allow(dead_code)]
+
+// FIXME This should compile, but it currently doesn't
+
+use std::fmt::Debug;
+
+type Foo = impl Debug;
+//~^ ERROR: could not find defining uses
+
+fn foo1() -> u32 {
+    let x: Foo = 22_u32;
+    //~^ ERROR: mismatched types [E0308]
+    x
+    //~^ ERROR: mismatched types [E0308]
+}
+
+fn foo2() -> u32 {
+    let x: Foo = 22_u32;
+    //~^ ERROR: mismatched types [E0308]
+    let y: Foo = x;
+    same_type((x, y));
+    y
+    //~^ ERROR: mismatched types [E0308]
+}
+
+fn same_type<T>(x: (T, T)) {}
+
+fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/type_of_a_let.stderr b/src/test/ui/type-alias-impl-trait/type_of_a_let.stderr
new file mode 100644
index 00000000000..cac8d6841af
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/type_of_a_let.stderr
@@ -0,0 +1,67 @@
+error[E0308]: mismatched types
+  --> $DIR/type_of_a_let.rs:12:18
+   |
+LL | type Foo = impl Debug;
+   |            ---------- the expected opaque type
+...
+LL |     let x: Foo = 22_u32;
+   |            ---   ^^^^^^ expected opaque type, found `u32`
+   |            |
+   |            expected due to this
+   |
+   = note: expected opaque type `impl Debug`
+                     found type `u32`
+
+error[E0308]: mismatched types
+  --> $DIR/type_of_a_let.rs:14:5
+   |
+LL | type Foo = impl Debug;
+   |            ---------- the found opaque type
+...
+LL | fn foo1() -> u32 {
+   |              --- expected `u32` because of return type
+...
+LL |     x
+   |     ^ expected `u32`, found opaque type
+   |
+   = note:     expected type `u32`
+           found opaque type `impl Debug`
+
+error[E0308]: mismatched types
+  --> $DIR/type_of_a_let.rs:19:18
+   |
+LL | type Foo = impl Debug;
+   |            ---------- the expected opaque type
+...
+LL |     let x: Foo = 22_u32;
+   |            ---   ^^^^^^ expected opaque type, found `u32`
+   |            |
+   |            expected due to this
+   |
+   = note: expected opaque type `impl Debug`
+                     found type `u32`
+
+error[E0308]: mismatched types
+  --> $DIR/type_of_a_let.rs:23:5
+   |
+LL | type Foo = impl Debug;
+   |            ---------- the found opaque type
+...
+LL | fn foo2() -> u32 {
+   |              --- expected `u32` because of return type
+...
+LL |     y
+   |     ^ expected `u32`, found opaque type
+   |
+   = note:     expected type `u32`
+           found opaque type `impl Debug`
+
+error: could not find defining uses
+  --> $DIR/type_of_a_let.rs:8:12
+   |
+LL | type Foo = impl Debug;
+   |            ^^^^^^^^^^
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/type-alias-impl-trait/type_of_a_let2.rs b/src/test/ui/type-alias-impl-trait/type_of_a_let2.rs
new file mode 100644
index 00000000000..33d3f164ce1
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/type_of_a_let2.rs
@@ -0,0 +1,25 @@
+#![feature(type_alias_impl_trait)]
+#![allow(dead_code)]
+
+// FIXME This should be under a feature flag
+
+use std::fmt::Debug;
+
+fn foo1() -> u32 {
+    let x: impl Debug = 22_u32;
+    //~^ ERROR: `impl Trait` not allowed outside of function and method return types [E0562]
+    x // ERROR: we only know x: Debug, we don't know x = u32
+}
+
+fn foo2() -> u32 {
+    let x: impl Debug = 22_u32;
+    //~^ ERROR: `impl Trait` not allowed outside of function and method return types [E0562]
+    let y: impl Debug = x;
+    //~^ ERROR: `impl Trait` not allowed outside of function and method return types [E0562]
+    same_type((x, y)); // ERROR
+    x
+}
+
+fn same_type<T>(x: (T, T)) {}
+
+fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/type_of_a_let2.stderr b/src/test/ui/type-alias-impl-trait/type_of_a_let2.stderr
new file mode 100644
index 00000000000..7a1825a8e2d
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/type_of_a_let2.stderr
@@ -0,0 +1,21 @@
+error[E0562]: `impl Trait` not allowed outside of function and method return types
+  --> $DIR/type_of_a_let2.rs:9:12
+   |
+LL |     let x: impl Debug = 22_u32;
+   |            ^^^^^^^^^^
+
+error[E0562]: `impl Trait` not allowed outside of function and method return types
+  --> $DIR/type_of_a_let2.rs:15:12
+   |
+LL |     let x: impl Debug = 22_u32;
+   |            ^^^^^^^^^^
+
+error[E0562]: `impl Trait` not allowed outside of function and method return types
+  --> $DIR/type_of_a_let2.rs:17:12
+   |
+LL |     let y: impl Debug = x;
+   |            ^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0562`.