let_chains: --bless tests due to recovery in lowering.

4 files changed, 905 insertions, 94 deletions

diff --git a/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.rs b/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.rs
index 43e0ee8a86c..7d1e5c3d64d 100644
--- a/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.rs
+++ b/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.rs
@@ -1,4 +1,4 @@
-// Here we test that `ast_validation` behaves correctly wrt. `let $pats = $expr` expressions.
+// Here we test that `lowering` behaves correctly wrt. `let $pats = $expr` expressions.
 //
 // We want to make sure that `let` is banned in situations other than:
 //
@@ -30,17 +30,22 @@ fn main() {}
 
 fn nested_within_if_expr() {
     if &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
-    //~^ ERROR `let` expressions only supported in `if`
+    //~^ ERROR mismatched types
 
     if !let 0 = 0 {} //~ ERROR `let` expressions are not supported here
     if *let 0 = 0 {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR type `bool` cannot be dereferenced
     if -let 0 = 0 {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR cannot apply unary operator `-` to type `bool`
 
     fn _check_try_binds_tighter() -> Result<(), ()> {
         if let 0 = 0? {}
+        //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
         Ok(())
     }
     if (let 0 = 0)? {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
+    //~| ERROR the `?` operator can only be used in a function that returns `Result`
 
     if true || let 0 = 0 {} //~ ERROR `let` expressions are not supported here
     if (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
@@ -49,42 +54,62 @@ fn nested_within_if_expr() {
 
     let mut x = true;
     if x = let 0 = 0 {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
 
     if true..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
     if ..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
     if (let 0 = 0).. {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
 
     // Binds as `(let ... = true)..true &&/|| false`.
     if let Range { start: _, end: _ } = true..true && false {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
     if let Range { start: _, end: _ } = true..true || false {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
 
     // Binds as `(let Range { start: F, end } = F)..(|| true)`.
     const F: fn() -> bool = || true;
     if let Range { start: F, end } = F..|| true {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
 
     // Binds as `(let Range { start: true, end } = t)..(&&false)`.
     let t = &&true;
     if let Range { start: true, end } = t..&&false {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
 
     if let true = let true = true {} //~ ERROR `let` expressions are not supported here
 }
 
 fn nested_within_while_expr() {
     while &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
 
     while !let 0 = 0 {} //~ ERROR `let` expressions are not supported here
     while *let 0 = 0 {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR type `bool` cannot be dereferenced
     while -let 0 = 0 {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR cannot apply unary operator `-` to type `bool`
 
     fn _check_try_binds_tighter() -> Result<(), ()> {
         while let 0 = 0? {}
+        //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
         Ok(())
     }
     while (let 0 = 0)? {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
+    //~| ERROR the `?` operator can only be used in a function that returns `Result`
 
     while true || let 0 = 0 {} //~ ERROR `let` expressions are not supported here
     while (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
@@ -93,26 +118,40 @@ fn nested_within_while_expr() {
 
     let mut x = true;
     while x = let 0 = 0 {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
 
     while true..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
     while ..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
     while (let 0 = 0).. {} //~ ERROR `let` expressions are not supported here
+    //~^ ERROR mismatched types
 
     // Binds as `(let ... = true)..true &&/|| false`.
     while let Range { start: _, end: _ } = true..true && false {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
     while let Range { start: _, end: _ } = true..true || false {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
 
     // Binds as `(let Range { start: F, end } = F)..(|| true)`.
     const F: fn() -> bool = || true;
     while let Range { start: F, end } = F..|| true {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
 
     // Binds as `(let Range { start: true, end } = t)..(&&false)`.
     let t = &&true;
     while let Range { start: true, end } = t..&&false {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
+    //~| ERROR mismatched types
 
     while let true = let true = true {} //~ ERROR `let` expressions are not supported here
 }
@@ -132,13 +171,18 @@ fn outside_if_and_while_expr() {
 
     !let 0 = 0; //~ ERROR `let` expressions are not supported here
     *let 0 = 0; //~ ERROR `let` expressions are not supported here
+    //~^ ERROR type `bool` cannot be dereferenced
     -let 0 = 0; //~ ERROR `let` expressions are not supported here
+    //~^ ERROR cannot apply unary operator `-` to type `bool`
 
     fn _check_try_binds_tighter() -> Result<(), ()> {
         let 0 = 0?;
+        //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
         Ok(())
     }
     (let 0 = 0)?; //~ ERROR `let` expressions are not supported here
+    //~^ ERROR the `?` operator can only be used in a function that returns `Result`
+    //~| ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
 
     true || let 0 = 0; //~ ERROR `let` expressions are not supported here
     (true || let 0 = 0); //~ ERROR `let` expressions are not supported here
@@ -153,6 +197,7 @@ fn outside_if_and_while_expr() {
 
     (let Range { start: _, end: _ } = true..true || false);
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
 
     (let true = let true = true);
     //~^ ERROR `let` expressions are not supported here
@@ -161,6 +206,7 @@ fn outside_if_and_while_expr() {
     // Check function tail position.
     &let 0 = 0
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR mismatched types
 }
 
 // Let's make sure that `let` inside const generic arguments are considered.
@@ -170,14 +216,20 @@ fn inside_const_generic_arguments() {
 
     if let A::<{
         true && let 1 = 1 //~ ERROR `let` expressions are not supported here
+        //~^ ERROR constant contains unimplemented expression type
+        //~| ERROR constant contains unimplemented expression type
     }>::O = 5 {}
 
     while let A::<{
         true && let 1 = 1 //~ ERROR `let` expressions are not supported here
+        //~^ ERROR constant contains unimplemented expression type
+        //~| ERROR constant contains unimplemented expression type
     }>::O = 5 {}
 
     if A::<{
         true && let 1 = 1 //~ ERROR `let` expressions are not supported here
+        //~^ ERROR constant contains unimplemented expression type
+        //~| ERROR constant contains unimplemented expression type
     }>::O == 5 {}
 
     // In the cases above we have `ExprKind::Block` to help us out.
diff --git a/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr b/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr
index 86baa038c0b..207d0d6d6b8 100644
--- a/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr
+++ b/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr
@@ -1,5 +1,5 @@
 error: expected one of `,` or `>`, found `&&`
-  --> $DIR/disallowed-positions.rs:190:14
+  --> $DIR/disallowed-positions.rs:242:14
    |
 LL |         true && let 1 = 1
    |              ^^ expected one of `,` or `>` here
@@ -44,7 +44,7 @@ LL |     if *let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:37:9
+  --> $DIR/disallowed-positions.rs:38:9
    |
 LL |     if -let 0 = 0 {}
    |         ^^^^^^^^^
@@ -53,7 +53,7 @@ LL |     if -let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:43:9
+  --> $DIR/disallowed-positions.rs:46:9
    |
 LL |     if (let 0 = 0)? {}
    |         ^^^^^^^^^
@@ -62,7 +62,7 @@ LL |     if (let 0 = 0)? {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:45:16
+  --> $DIR/disallowed-positions.rs:50:16
    |
 LL |     if true || let 0 = 0 {}
    |                ^^^^^^^^^
@@ -71,7 +71,7 @@ LL |     if true || let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:46:17
+  --> $DIR/disallowed-positions.rs:51:17
    |
 LL |     if (true || let 0 = 0) {}
    |                 ^^^^^^^^^
@@ -80,7 +80,7 @@ LL |     if (true || let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:47:25
+  --> $DIR/disallowed-positions.rs:52:25
    |
 LL |     if true && (true || let 0 = 0) {}
    |                         ^^^^^^^^^
@@ -89,7 +89,7 @@ LL |     if true && (true || let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:48:25
+  --> $DIR/disallowed-positions.rs:53:25
    |
 LL |     if true || (true && let 0 = 0) {}
    |                         ^^^^^^^^^
@@ -98,7 +98,7 @@ LL |     if true || (true && let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:51:12
+  --> $DIR/disallowed-positions.rs:56:12
    |
 LL |     if x = let 0 = 0 {}
    |            ^^^^^^^^^
@@ -107,7 +107,7 @@ LL |     if x = let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:53:15
+  --> $DIR/disallowed-positions.rs:59:15
    |
 LL |     if true..(let 0 = 0) {}
    |               ^^^^^^^^^
@@ -116,7 +116,7 @@ LL |     if true..(let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:54:11
+  --> $DIR/disallowed-positions.rs:61:11
    |
 LL |     if ..(let 0 = 0) {}
    |           ^^^^^^^^^
@@ -125,7 +125,7 @@ LL |     if ..(let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:55:9
+  --> $DIR/disallowed-positions.rs:63:9
    |
 LL |     if (let 0 = 0).. {}
    |         ^^^^^^^^^
@@ -134,7 +134,7 @@ LL |     if (let 0 = 0).. {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:58:8
+  --> $DIR/disallowed-positions.rs:67:8
    |
 LL |     if let Range { start: _, end: _ } = true..true && false {}
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -143,7 +143,7 @@ LL |     if let Range { start: _, end: _ } = true..true && false {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:60:8
+  --> $DIR/disallowed-positions.rs:71:8
    |
 LL |     if let Range { start: _, end: _ } = true..true || false {}
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -152,7 +152,7 @@ LL |     if let Range { start: _, end: _ } = true..true || false {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:65:8
+  --> $DIR/disallowed-positions.rs:78:8
    |
 LL |     if let Range { start: F, end } = F..|| true {}
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -161,7 +161,7 @@ LL |     if let Range { start: F, end } = F..|| true {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:70:8
+  --> $DIR/disallowed-positions.rs:86:8
    |
 LL |     if let Range { start: true, end } = t..&&false {}
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -170,7 +170,7 @@ LL |     if let Range { start: true, end } = t..&&false {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:73:19
+  --> $DIR/disallowed-positions.rs:92:19
    |
 LL |     if let true = let true = true {}
    |                   ^^^^^^^^^^^^^^^
@@ -179,7 +179,7 @@ LL |     if let true = let true = true {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:77:12
+  --> $DIR/disallowed-positions.rs:96:12
    |
 LL |     while &let 0 = 0 {}
    |            ^^^^^^^^^
@@ -188,7 +188,7 @@ LL |     while &let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:79:12
+  --> $DIR/disallowed-positions.rs:99:12
    |
 LL |     while !let 0 = 0 {}
    |            ^^^^^^^^^
@@ -197,7 +197,7 @@ LL |     while !let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:80:12
+  --> $DIR/disallowed-positions.rs:100:12
    |
 LL |     while *let 0 = 0 {}
    |            ^^^^^^^^^
@@ -206,7 +206,7 @@ LL |     while *let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:81:12
+  --> $DIR/disallowed-positions.rs:102:12
    |
 LL |     while -let 0 = 0 {}
    |            ^^^^^^^^^
@@ -215,7 +215,7 @@ LL |     while -let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:87:12
+  --> $DIR/disallowed-positions.rs:110:12
    |
 LL |     while (let 0 = 0)? {}
    |            ^^^^^^^^^
@@ -224,7 +224,7 @@ LL |     while (let 0 = 0)? {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:89:19
+  --> $DIR/disallowed-positions.rs:114:19
    |
 LL |     while true || let 0 = 0 {}
    |                   ^^^^^^^^^
@@ -233,7 +233,7 @@ LL |     while true || let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:90:20
+  --> $DIR/disallowed-positions.rs:115:20
    |
 LL |     while (true || let 0 = 0) {}
    |                    ^^^^^^^^^
@@ -242,7 +242,7 @@ LL |     while (true || let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:91:28
+  --> $DIR/disallowed-positions.rs:116:28
    |
 LL |     while true && (true || let 0 = 0) {}
    |                            ^^^^^^^^^
@@ -251,7 +251,7 @@ LL |     while true && (true || let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:92:28
+  --> $DIR/disallowed-positions.rs:117:28
    |
 LL |     while true || (true && let 0 = 0) {}
    |                            ^^^^^^^^^
@@ -260,7 +260,7 @@ LL |     while true || (true && let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:95:15
+  --> $DIR/disallowed-positions.rs:120:15
    |
 LL |     while x = let 0 = 0 {}
    |               ^^^^^^^^^
@@ -269,7 +269,7 @@ LL |     while x = let 0 = 0 {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:97:18
+  --> $DIR/disallowed-positions.rs:123:18
    |
 LL |     while true..(let 0 = 0) {}
    |                  ^^^^^^^^^
@@ -278,7 +278,7 @@ LL |     while true..(let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:98:14
+  --> $DIR/disallowed-positions.rs:125:14
    |
 LL |     while ..(let 0 = 0) {}
    |              ^^^^^^^^^
@@ -287,7 +287,7 @@ LL |     while ..(let 0 = 0) {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:99:12
+  --> $DIR/disallowed-positions.rs:127:12
    |
 LL |     while (let 0 = 0).. {}
    |            ^^^^^^^^^
@@ -296,7 +296,7 @@ LL |     while (let 0 = 0).. {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:102:11
+  --> $DIR/disallowed-positions.rs:131:11
    |
 LL |     while let Range { start: _, end: _ } = true..true && false {}
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -305,7 +305,7 @@ LL |     while let Range { start: _, end: _ } = true..true && false {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:104:11
+  --> $DIR/disallowed-positions.rs:135:11
    |
 LL |     while let Range { start: _, end: _ } = true..true || false {}
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -314,7 +314,7 @@ LL |     while let Range { start: _, end: _ } = true..true || false {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:109:11
+  --> $DIR/disallowed-positions.rs:142:11
    |
 LL |     while let Range { start: F, end } = F..|| true {}
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -323,7 +323,7 @@ LL |     while let Range { start: F, end } = F..|| true {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:114:11
+  --> $DIR/disallowed-positions.rs:150:11
    |
 LL |     while let Range { start: true, end } = t..&&false {}
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -332,7 +332,7 @@ LL |     while let Range { start: true, end } = t..&&false {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:117:22
+  --> $DIR/disallowed-positions.rs:156:22
    |
 LL |     while let true = let true = true {}
    |                      ^^^^^^^^^^^^^^^
@@ -341,7 +341,7 @@ LL |     while let true = let true = true {}
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:131:6
+  --> $DIR/disallowed-positions.rs:170:6
    |
 LL |     &let 0 = 0;
    |      ^^^^^^^^^
@@ -350,7 +350,7 @@ LL |     &let 0 = 0;
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:133:6
+  --> $DIR/disallowed-positions.rs:172:6
    |
 LL |     !let 0 = 0;
    |      ^^^^^^^^^
@@ -359,7 +359,7 @@ LL |     !let 0 = 0;
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:134:6
+  --> $DIR/disallowed-positions.rs:173:6
    |
 LL |     *let 0 = 0;
    |      ^^^^^^^^^
@@ -368,7 +368,7 @@ LL |     *let 0 = 0;
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:135:6
+  --> $DIR/disallowed-positions.rs:175:6
    |
 LL |     -let 0 = 0;
    |      ^^^^^^^^^
@@ -377,7 +377,7 @@ LL |     -let 0 = 0;
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:141:6
+  --> $DIR/disallowed-positions.rs:183:6
    |
 LL |     (let 0 = 0)?;
    |      ^^^^^^^^^
@@ -386,7 +386,7 @@ LL |     (let 0 = 0)?;
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:143:13
+  --> $DIR/disallowed-positions.rs:187:13
    |
 LL |     true || let 0 = 0;
    |             ^^^^^^^^^
@@ -395,7 +395,7 @@ LL |     true || let 0 = 0;
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:144:14
+  --> $DIR/disallowed-positions.rs:188:14
    |
 LL |     (true || let 0 = 0);
    |              ^^^^^^^^^
@@ -404,7 +404,7 @@ LL |     (true || let 0 = 0);
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:145:22
+  --> $DIR/disallowed-positions.rs:189:22
    |
 LL |     true && (true || let 0 = 0);
    |                      ^^^^^^^^^
@@ -413,7 +413,7 @@ LL |     true && (true || let 0 = 0);
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:148:9
+  --> $DIR/disallowed-positions.rs:192:9
    |
 LL |     x = let 0 = 0;
    |         ^^^^^^^^^
@@ -422,7 +422,7 @@ LL |     x = let 0 = 0;
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:150:12
+  --> $DIR/disallowed-positions.rs:194:12
    |
 LL |     true..(let 0 = 0);
    |            ^^^^^^^^^
@@ -431,7 +431,7 @@ LL |     true..(let 0 = 0);
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:151:8
+  --> $DIR/disallowed-positions.rs:195:8
    |
 LL |     ..(let 0 = 0);
    |        ^^^^^^^^^
@@ -440,7 +440,7 @@ LL |     ..(let 0 = 0);
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:152:6
+  --> $DIR/disallowed-positions.rs:196:6
    |
 LL |     (let 0 = 0)..;
    |      ^^^^^^^^^
@@ -449,7 +449,7 @@ LL |     (let 0 = 0)..;
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:154:6
+  --> $DIR/disallowed-positions.rs:198:6
    |
 LL |     (let Range { start: _, end: _ } = true..true || false);
    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -458,7 +458,7 @@ LL |     (let Range { start: _, end: _ } = true..true || false);
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:157:6
+  --> $DIR/disallowed-positions.rs:202:6
    |
 LL |     (let true = let true = true);
    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -467,7 +467,7 @@ LL |     (let true = let true = true);
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:157:17
+  --> $DIR/disallowed-positions.rs:202:17
    |
 LL |     (let true = let true = true);
    |                 ^^^^^^^^^^^^^^^
@@ -476,7 +476,7 @@ LL |     (let true = let true = true);
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:162:6
+  --> $DIR/disallowed-positions.rs:207:6
    |
 LL |     &let 0 = 0
    |      ^^^^^^^^^
@@ -485,7 +485,7 @@ LL |     &let 0 = 0
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:172:17
+  --> $DIR/disallowed-positions.rs:218:17
    |
 LL |         true && let 1 = 1
    |                 ^^^^^^^^^
@@ -494,7 +494,7 @@ LL |         true && let 1 = 1
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:176:17
+  --> $DIR/disallowed-positions.rs:224:17
    |
 LL |         true && let 1 = 1
    |                 ^^^^^^^^^
@@ -503,7 +503,7 @@ LL |         true && let 1 = 1
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
 error: `let` expressions are not supported here
-  --> $DIR/disallowed-positions.rs:180:17
+  --> $DIR/disallowed-positions.rs:230:17
    |
 LL |         true && let 1 = 1
    |                 ^^^^^^^^^
@@ -511,11 +511,477 @@ LL |         true && let 1 = 1
    = note: only supported directly in conditions of `if`- and `while`-expressions
    = note: as well as when nested within `&&` and parenthesis in those conditions
 
-error: `let` expressions only supported in `if`
-  --> $DIR/disallowed-positions.rs:32:9
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:32:8
    |
 LL |     if &let 0 = 0 {}
-   |         ^^^^^^^^^
+   |        ^^^^^^^^^^ expected bool, found &bool
+   |
+   = note: expected type `bool`
+              found type `&bool`
+
+error[E0614]: type `bool` cannot be dereferenced
+  --> $DIR/disallowed-positions.rs:36:8
+   |
+LL |     if *let 0 = 0 {}
+   |        ^^^^^^^^^^
+
+error[E0600]: cannot apply unary operator `-` to type `bool`
+  --> $DIR/disallowed-positions.rs:38:8
+   |
+LL |     if -let 0 = 0 {}
+   |        ^^^^^^^^^^ cannot apply unary operator `-`
+   |
+   = note: an implementation of `std::ops::Neg` might be missing for `bool`
+
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/disallowed-positions.rs:46:8
+   |
+LL |     if (let 0 = 0)? {}
+   |        ^^^^^^^^^^^^ the `?` operator cannot be applied to type `bool`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `bool`
+   = note: required by `std::ops::Try::into_result`
+
+error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
+  --> $DIR/disallowed-positions.rs:46:8
+   |
+LL |     if (let 0 = 0)? {}
+   |        ^^^^^^^^^^^^ cannot use the `?` operator in a function that returns `()`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `()`
+   = note: required by `std::ops::Try::from_error`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:56:8
+   |
+LL |     if x = let 0 = 0 {}
+   |        ^^^^^^^^^^^^^
+   |        |
+   |        expected bool, found ()
+   |        help: try comparing for equality: `x == let 0 = 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:59:8
+   |
+LL |     if true..(let 0 = 0) {}
+   |        ^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:61:8
+   |
+LL |     if ..(let 0 = 0) {}
+   |        ^^^^^^^^^^^^^ expected bool, found struct `std::ops::RangeTo`
+   |
+   = note: expected type `bool`
+              found type `std::ops::RangeTo<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:63:8
+   |
+LL |     if (let 0 = 0).. {}
+   |        ^^^^^^^^^^^^^ expected bool, found struct `std::ops::RangeFrom`
+   |
+   = note: expected type `bool`
+              found type `std::ops::RangeFrom<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:67:12
+   |
+LL |     if let Range { start: _, end: _ } = true..true && false {}
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^   ---- this match expression has type `bool`
+   |            |
+   |            expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:67:8
+   |
+LL |     if let Range { start: _, end: _ } = true..true && false {}
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:71:12
+   |
+LL |     if let Range { start: _, end: _ } = true..true || false {}
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^   ---- this match expression has type `bool`
+   |            |
+   |            expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:71:8
+   |
+LL |     if let Range { start: _, end: _ } = true..true || false {}
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:78:12
+   |
+LL |     if let Range { start: F, end } = F..|| true {}
+   |            ^^^^^^^^^^^^^^^^^^^^^^^ expected fn pointer, found struct `std::ops::Range`
+   |
+   = note: expected type `fn() -> bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:78:41
+   |
+LL |     if let Range { start: F, end } = F..|| true {}
+   |                                         ^^^^^^^ expected bool, found closure
+   |
+   = note: expected type `bool`
+              found type `[closure@$DIR/disallowed-positions.rs:78:41: 78:48]`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:78:8
+   |
+LL |     if let Range { start: F, end } = F..|| true {}
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:86:12
+   |
+LL |     if let Range { start: true, end } = t..&&false {}
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^   - this match expression has type `bool`
+   |            |
+   |            expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:86:44
+   |
+LL |     if let Range { start: true, end } = t..&&false {}
+   |                                            ^^^^^^^ expected bool, found &&bool
+   |
+   = note: expected type `bool`
+              found type `&&bool`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:86:8
+   |
+LL |     if let Range { start: true, end } = t..&&false {}
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/disallowed-positions.rs:42:20
+   |
+LL |         if let 0 = 0? {}
+   |                    ^^ the `?` operator cannot be applied to type `{integer}`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `{integer}`
+   = note: required by `std::ops::Try::into_result`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:96:11
+   |
+LL |     while &let 0 = 0 {}
+   |           ^^^^^^^^^^ expected bool, found &bool
+   |
+   = note: expected type `bool`
+              found type `&bool`
+
+error[E0614]: type `bool` cannot be dereferenced
+  --> $DIR/disallowed-positions.rs:100:11
+   |
+LL |     while *let 0 = 0 {}
+   |           ^^^^^^^^^^
+
+error[E0600]: cannot apply unary operator `-` to type `bool`
+  --> $DIR/disallowed-positions.rs:102:11
+   |
+LL |     while -let 0 = 0 {}
+   |           ^^^^^^^^^^ cannot apply unary operator `-`
+   |
+   = note: an implementation of `std::ops::Neg` might be missing for `bool`
+
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/disallowed-positions.rs:110:11
+   |
+LL |     while (let 0 = 0)? {}
+   |           ^^^^^^^^^^^^ the `?` operator cannot be applied to type `bool`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `bool`
+   = note: required by `std::ops::Try::into_result`
+
+error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
+  --> $DIR/disallowed-positions.rs:110:11
+   |
+LL |     while (let 0 = 0)? {}
+   |           ^^^^^^^^^^^^ cannot use the `?` operator in a function that returns `()`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `()`
+   = note: required by `std::ops::Try::from_error`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:120:11
+   |
+LL |     while x = let 0 = 0 {}
+   |           ^^^^^^^^^^^^^
+   |           |
+   |           expected bool, found ()
+   |           help: try comparing for equality: `x == let 0 = 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:123:11
+   |
+LL |     while true..(let 0 = 0) {}
+   |           ^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:125:11
+   |
+LL |     while ..(let 0 = 0) {}
+   |           ^^^^^^^^^^^^^ expected bool, found struct `std::ops::RangeTo`
+   |
+   = note: expected type `bool`
+              found type `std::ops::RangeTo<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:127:11
+   |
+LL |     while (let 0 = 0).. {}
+   |           ^^^^^^^^^^^^^ expected bool, found struct `std::ops::RangeFrom`
+   |
+   = note: expected type `bool`
+              found type `std::ops::RangeFrom<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:131:15
+   |
+LL |     while let Range { start: _, end: _ } = true..true && false {}
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^   ---- this match expression has type `bool`
+   |               |
+   |               expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:131:11
+   |
+LL |     while let Range { start: _, end: _ } = true..true && false {}
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:135:15
+   |
+LL |     while let Range { start: _, end: _ } = true..true || false {}
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^   ---- this match expression has type `bool`
+   |               |
+   |               expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:135:11
+   |
+LL |     while let Range { start: _, end: _ } = true..true || false {}
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:142:15
+   |
+LL |     while let Range { start: F, end } = F..|| true {}
+   |               ^^^^^^^^^^^^^^^^^^^^^^^ expected fn pointer, found struct `std::ops::Range`
+   |
+   = note: expected type `fn() -> bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:142:44
+   |
+LL |     while let Range { start: F, end } = F..|| true {}
+   |                                            ^^^^^^^ expected bool, found closure
+   |
+   = note: expected type `bool`
+              found type `[closure@$DIR/disallowed-positions.rs:142:44: 142:51]`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:142:11
+   |
+LL |     while let Range { start: F, end } = F..|| true {}
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:150:15
+   |
+LL |     while let Range { start: true, end } = t..&&false {}
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^   - this match expression has type `bool`
+   |               |
+   |               expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:150:47
+   |
+LL |     while let Range { start: true, end } = t..&&false {}
+   |                                               ^^^^^^^ expected bool, found &&bool
+   |
+   = note: expected type `bool`
+              found type `&&bool`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:150:11
+   |
+LL |     while let Range { start: true, end } = t..&&false {}
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<bool>`
+
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/disallowed-positions.rs:106:23
+   |
+LL |         while let 0 = 0? {}
+   |                       ^^ the `?` operator cannot be applied to type `{integer}`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `{integer}`
+   = note: required by `std::ops::Try::into_result`
+
+error[E0614]: type `bool` cannot be dereferenced
+  --> $DIR/disallowed-positions.rs:173:5
+   |
+LL |     *let 0 = 0;
+   |     ^^^^^^^^^^
+
+error[E0600]: cannot apply unary operator `-` to type `bool`
+  --> $DIR/disallowed-positions.rs:175:5
+   |
+LL |     -let 0 = 0;
+   |     ^^^^^^^^^^ cannot apply unary operator `-`
+   |
+   = note: an implementation of `std::ops::Neg` might be missing for `bool`
+
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/disallowed-positions.rs:183:5
+   |
+LL |     (let 0 = 0)?;
+   |     ^^^^^^^^^^^^ the `?` operator cannot be applied to type `bool`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `bool`
+   = note: required by `std::ops::Try::into_result`
+
+error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
+  --> $DIR/disallowed-positions.rs:183:5
+   |
+LL |     (let 0 = 0)?;
+   |     ^^^^^^^^^^^^ cannot use the `?` operator in a function that returns `()`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `()`
+   = note: required by `std::ops::Try::from_error`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:198:10
+   |
+LL |     (let Range { start: _, end: _ } = true..true || false);
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^   ---- this match expression has type `bool`
+   |          |
+   |          expected bool, found struct `std::ops::Range`
+   |
+   = note: expected type `bool`
+              found type `std::ops::Range<_>`
+
+error[E0308]: mismatched types
+  --> $DIR/disallowed-positions.rs:207:5
+   |
+LL | fn outside_if_and_while_expr() {
+   |                                - help: try adding a return type: `-> &bool`
+...
+LL |     &let 0 = 0
+   |     ^^^^^^^^^^ expected (), found &bool
+   |
+   = note: expected type `()`
+              found type `&bool`
+
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/disallowed-positions.rs:179:17
+   |
+LL |         let 0 = 0?;
+   |                 ^^ the `?` operator cannot be applied to type `{integer}`
+   |
+   = help: the trait `std::ops::Try` is not implemented for `{integer}`
+   = note: required by `std::ops::Try::into_result`
+
+error[E0019]: constant contains unimplemented expression type
+  --> $DIR/disallowed-positions.rs:218:25
+   |
+LL |         true && let 1 = 1
+   |                         ^
+
+error[E0019]: constant contains unimplemented expression type
+  --> $DIR/disallowed-positions.rs:218:21
+   |
+LL |         true && let 1 = 1
+   |                     ^
+
+error[E0019]: constant contains unimplemented expression type
+  --> $DIR/disallowed-positions.rs:224:25
+   |
+LL |         true && let 1 = 1
+   |                         ^
+
+error[E0019]: constant contains unimplemented expression type
+  --> $DIR/disallowed-positions.rs:224:21
+   |
+LL |         true && let 1 = 1
+   |                     ^
+
+error[E0019]: constant contains unimplemented expression type
+  --> $DIR/disallowed-positions.rs:230:25
+   |
+LL |         true && let 1 = 1
+   |                         ^
+
+error[E0019]: constant contains unimplemented expression type
+  --> $DIR/disallowed-positions.rs:230:21
+   |
+LL |         true && let 1 = 1
+   |                     ^
 
-error: aborting due to 57 previous errors
+error: aborting due to 109 previous errors
 
+Some errors have detailed explanations: E0019, E0277, E0308, E0600, E0614.
+For more information about an error, try `rustc --explain E0019`.
diff --git a/src/test/ui/rfc-2497-if-let-chains/feature-gate.rs b/src/test/ui/rfc-2497-if-let-chains/feature-gate.rs
index c125ec89cb5..64987663adb 100644
--- a/src/test/ui/rfc-2497-if-let-chains/feature-gate.rs
+++ b/src/test/ui/rfc-2497-if-let-chains/feature-gate.rs
@@ -13,26 +13,33 @@ fn _if() {
 
     if (let 0 = 1) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
-    //~| ERROR `let` expressions only supported in `if`
+    //~| ERROR `let` expressions are not supported here
 
     if (((let 0 = 1))) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     if true && let 0 = 1 {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     if let 0 = 1 && true {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     if (let 0 = 1) && true {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     if true && (let 0 = 1) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     if (let 0 = 1) && (let 0 = 1) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
     //~| ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
 
     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
@@ -40,35 +47,49 @@ fn _if() {
     //~| ERROR `let` expressions in this position are experimental [E0658]
     //~| ERROR `let` expressions in this position are experimental [E0658]
     //~| ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
 
     if let Range { start: _, end: _ } = (true..true) && false {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 }
 
 fn _while() {
-    if let 0 = 1 {} // Stable!
+    while let 0 = 1 {} // Stable!
 
     while (let 0 = 1) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     while (((let 0 = 1))) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     while true && let 0 = 1 {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     while let 0 = 1 && true {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     while (let 0 = 1) && true {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     while true && (let 0 = 1) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 
     while (let 0 = 1) && (let 0 = 1) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
     //~| ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
 
     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
@@ -76,9 +97,15 @@ fn _while() {
     //~| ERROR `let` expressions in this position are experimental [E0658]
     //~| ERROR `let` expressions in this position are experimental [E0658]
     //~| ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
 
     while let Range { start: _, end: _ } = (true..true) && false {}
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
 }
 
 fn _macros() {
@@ -95,8 +122,10 @@ fn _macros() {
     }
     use_expr!((let 0 = 1 && 0 == 0));
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
     use_expr!((let 0 = 1));
     //~^ ERROR `let` expressions in this position are experimental [E0658]
+    //~| ERROR `let` expressions are not supported here
     #[cfg(FALSE)] (let 0 = 1);
     //~^ ERROR `let` expressions in this position are experimental [E0658]
     use_expr!(let 0 = 1);
diff --git a/src/test/ui/rfc-2497-if-let-chains/feature-gate.stderr b/src/test/ui/rfc-2497-if-let-chains/feature-gate.stderr
index 5ed0dd3cab6..6167427fa9f 100644
--- a/src/test/ui/rfc-2497-if-let-chains/feature-gate.stderr
+++ b/src/test/ui/rfc-2497-if-let-chains/feature-gate.stderr
@@ -1,5 +1,5 @@
 error: no rules expected the token `let`
-  --> $DIR/feature-gate.rs:102:15
+  --> $DIR/feature-gate.rs:131:15
    |
 LL |     macro_rules! use_expr {
    |     --------------------- when calling this macro
@@ -26,7 +26,7 @@ LL |     if (((let 0 = 1))) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:21:16
+  --> $DIR/feature-gate.rs:22:16
    |
 LL |     if true && let 0 = 1 {}
    |                ^^^^^^^^^
@@ -35,7 +35,7 @@ LL |     if true && let 0 = 1 {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:24:8
+  --> $DIR/feature-gate.rs:26:8
    |
 LL |     if let 0 = 1 && true {}
    |        ^^^^^^^^^
@@ -44,7 +44,7 @@ LL |     if let 0 = 1 && true {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:27:9
+  --> $DIR/feature-gate.rs:30:9
    |
 LL |     if (let 0 = 1) && true {}
    |         ^^^^^^^^^
@@ -53,7 +53,7 @@ LL |     if (let 0 = 1) && true {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:30:17
+  --> $DIR/feature-gate.rs:34:17
    |
 LL |     if true && (let 0 = 1) {}
    |                 ^^^^^^^^^
@@ -62,7 +62,7 @@ LL |     if true && (let 0 = 1) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:33:9
+  --> $DIR/feature-gate.rs:38:9
    |
 LL |     if (let 0 = 1) && (let 0 = 1) {}
    |         ^^^^^^^^^
@@ -71,7 +71,7 @@ LL |     if (let 0 = 1) && (let 0 = 1) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:33:24
+  --> $DIR/feature-gate.rs:38:24
    |
 LL |     if (let 0 = 1) && (let 0 = 1) {}
    |                        ^^^^^^^^^
@@ -80,7 +80,7 @@ LL |     if (let 0 = 1) && (let 0 = 1) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:37:8
+  --> $DIR/feature-gate.rs:44:8
    |
 LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |        ^^^^^^^^^
@@ -89,7 +89,7 @@ LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:37:21
+  --> $DIR/feature-gate.rs:44:21
    |
 LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |                     ^^^^^^^^^
@@ -98,7 +98,7 @@ LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:37:35
+  --> $DIR/feature-gate.rs:44:35
    |
 LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |                                   ^^^^^^^^^
@@ -107,7 +107,7 @@ LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:37:48
+  --> $DIR/feature-gate.rs:44:48
    |
 LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |                                                ^^^^^^^^^
@@ -116,7 +116,7 @@ LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:37:61
+  --> $DIR/feature-gate.rs:44:61
    |
 LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |                                                             ^^^^^^^^^
@@ -125,7 +125,7 @@ LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:44:8
+  --> $DIR/feature-gate.rs:56:8
    |
 LL |     if let Range { start: _, end: _ } = (true..true) && false {}
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -134,7 +134,7 @@ LL |     if let Range { start: _, end: _ } = (true..true) && false {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:51:12
+  --> $DIR/feature-gate.rs:64:12
    |
 LL |     while (let 0 = 1) {}
    |            ^^^^^^^^^
@@ -143,7 +143,7 @@ LL |     while (let 0 = 1) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:54:14
+  --> $DIR/feature-gate.rs:68:14
    |
 LL |     while (((let 0 = 1))) {}
    |              ^^^^^^^^^
@@ -152,7 +152,7 @@ LL |     while (((let 0 = 1))) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:57:19
+  --> $DIR/feature-gate.rs:72:19
    |
 LL |     while true && let 0 = 1 {}
    |                   ^^^^^^^^^
@@ -161,7 +161,7 @@ LL |     while true && let 0 = 1 {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:60:11
+  --> $DIR/feature-gate.rs:76:11
    |
 LL |     while let 0 = 1 && true {}
    |           ^^^^^^^^^
@@ -170,7 +170,7 @@ LL |     while let 0 = 1 && true {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:63:12
+  --> $DIR/feature-gate.rs:80:12
    |
 LL |     while (let 0 = 1) && true {}
    |            ^^^^^^^^^
@@ -179,7 +179,7 @@ LL |     while (let 0 = 1) && true {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:66:20
+  --> $DIR/feature-gate.rs:84:20
    |
 LL |     while true && (let 0 = 1) {}
    |                    ^^^^^^^^^
@@ -188,7 +188,7 @@ LL |     while true && (let 0 = 1) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:69:12
+  --> $DIR/feature-gate.rs:88:12
    |
 LL |     while (let 0 = 1) && (let 0 = 1) {}
    |            ^^^^^^^^^
@@ -197,7 +197,7 @@ LL |     while (let 0 = 1) && (let 0 = 1) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:69:27
+  --> $DIR/feature-gate.rs:88:27
    |
 LL |     while (let 0 = 1) && (let 0 = 1) {}
    |                           ^^^^^^^^^
@@ -206,7 +206,7 @@ LL |     while (let 0 = 1) && (let 0 = 1) {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:73:11
+  --> $DIR/feature-gate.rs:94:11
    |
 LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |           ^^^^^^^^^
@@ -215,7 +215,7 @@ LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:73:24
+  --> $DIR/feature-gate.rs:94:24
    |
 LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |                        ^^^^^^^^^
@@ -224,7 +224,7 @@ LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:73:38
+  --> $DIR/feature-gate.rs:94:38
    |
 LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |                                      ^^^^^^^^^
@@ -233,7 +233,7 @@ LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:73:51
+  --> $DIR/feature-gate.rs:94:51
    |
 LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |                                                   ^^^^^^^^^
@@ -242,7 +242,7 @@ LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:73:64
+  --> $DIR/feature-gate.rs:94:64
    |
 LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
    |                                                                ^^^^^^^^^
@@ -251,7 +251,7 @@ LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:80:11
+  --> $DIR/feature-gate.rs:106:11
    |
 LL |     while let Range { start: _, end: _ } = (true..true) && false {}
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -260,7 +260,7 @@ LL |     while let Range { start: _, end: _ } = (true..true) && false {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:100:20
+  --> $DIR/feature-gate.rs:129:20
    |
 LL |     #[cfg(FALSE)] (let 0 = 1);
    |                    ^^^^^^^^^
@@ -269,7 +269,7 @@ LL |     #[cfg(FALSE)] (let 0 = 1);
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:87:17
+  --> $DIR/feature-gate.rs:114:17
    |
 LL |     noop_expr!((let 0 = 1));
    |                 ^^^^^^^^^
@@ -278,7 +278,7 @@ LL |     noop_expr!((let 0 = 1));
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:96:16
+  --> $DIR/feature-gate.rs:123:16
    |
 LL |     use_expr!((let 0 = 1 && 0 == 0));
    |                ^^^^^^^^^
@@ -287,7 +287,7 @@ LL |     use_expr!((let 0 = 1 && 0 == 0));
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:98:16
+  --> $DIR/feature-gate.rs:126:16
    |
 LL |     use_expr!((let 0 = 1));
    |                ^^^^^^^^^
@@ -295,12 +295,276 @@ LL |     use_expr!((let 0 = 1));
    = note: for more information, see https://github.com/rust-lang/rust/issues/53667
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
-error: `let` expressions only supported in `if`
+error: `let` expressions are not supported here
   --> $DIR/feature-gate.rs:14:9
    |
 LL |     if (let 0 = 1) {}
    |         ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:18:11
+   |
+LL |     if (((let 0 = 1))) {}
+   |           ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:22:16
+   |
+LL |     if true && let 0 = 1 {}
+   |                ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:26:8
+   |
+LL |     if let 0 = 1 && true {}
+   |        ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:30:9
+   |
+LL |     if (let 0 = 1) && true {}
+   |         ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:34:17
+   |
+LL |     if true && (let 0 = 1) {}
+   |                 ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:38:9
+   |
+LL |     if (let 0 = 1) && (let 0 = 1) {}
+   |         ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:38:24
+   |
+LL |     if (let 0 = 1) && (let 0 = 1) {}
+   |                        ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:44:8
+   |
+LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |        ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:44:21
+   |
+LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |                     ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:44:35
+   |
+LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |                                   ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:44:48
+   |
+LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |                                                ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:44:61
+   |
+LL |     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |                                                             ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:56:8
+   |
+LL |     if let Range { start: _, end: _ } = (true..true) && false {}
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:64:12
+   |
+LL |     while (let 0 = 1) {}
+   |            ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:68:14
+   |
+LL |     while (((let 0 = 1))) {}
+   |              ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:72:19
+   |
+LL |     while true && let 0 = 1 {}
+   |                   ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:76:11
+   |
+LL |     while let 0 = 1 && true {}
+   |           ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:80:12
+   |
+LL |     while (let 0 = 1) && true {}
+   |            ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:84:20
+   |
+LL |     while true && (let 0 = 1) {}
+   |                    ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:88:12
+   |
+LL |     while (let 0 = 1) && (let 0 = 1) {}
+   |            ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:88:27
+   |
+LL |     while (let 0 = 1) && (let 0 = 1) {}
+   |                           ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:94:11
+   |
+LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |           ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:94:24
+   |
+LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |                        ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:94:38
+   |
+LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |                                      ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:94:51
+   |
+LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |                                                   ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:94:64
+   |
+LL |     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+   |                                                                ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:106:11
+   |
+LL |     while let Range { start: _, end: _ } = (true..true) && false {}
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:123:16
+   |
+LL |     use_expr!((let 0 = 1 && 0 == 0));
+   |                ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
+
+error: `let` expressions are not supported here
+  --> $DIR/feature-gate.rs:126:16
+   |
+LL |     use_expr!((let 0 = 1));
+   |                ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if`- and `while`-expressions
+   = note: as well as when nested within `&&` and parenthesis in those conditions
 
-error: aborting due to 34 previous errors
+error: aborting due to 63 previous errors
 
 For more information about this error, try `rustc --explain E0658`.