Make expr_use_ctxt always return Some unless the syntax context changes.

tests/ui/ignored_unit_patterns.fixed

@@ -1,6 +1,11 @@
 //@aux-build:proc_macro_derive.rs
 #![warn(clippy::ignored_unit_patterns)]
-#![allow(clippy::let_unit_value, clippy::redundant_pattern_matching, clippy::single_match)]
+#![allow(
+    clippy::let_unit_value,
+    clippy::redundant_pattern_matching,
+    clippy::single_match,
+    clippy::needless_borrow
+)]
 
 fn foo() -> Result<(), ()> {
     unimplemented!()

tests/ui/ignored_unit_patterns.rs

@@ -1,6 +1,11 @@
 //@aux-build:proc_macro_derive.rs
 #![warn(clippy::ignored_unit_patterns)]
-#![allow(clippy::let_unit_value, clippy::redundant_pattern_matching, clippy::single_match)]
+#![allow(
+    clippy::let_unit_value,
+    clippy::redundant_pattern_matching,
+    clippy::single_match,
+    clippy::needless_borrow
+)]
 
 fn foo() -> Result<(), ()> {
     unimplemented!()

tests/ui/ignored_unit_patterns.stderr

@@ -1,5 +1,5 @@
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:11:12
+  --> $DIR/ignored_unit_patterns.rs:16:12
    |
 LL |         Ok(_) => {},
    |            ^ help: use `()` instead of `_`: `()`
@@ -8,49 +8,49 @@ LL |         Ok(_) => {},
    = help: to override `-D warnings` add `#[allow(clippy::ignored_unit_patterns)]`
 
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:12:13
+  --> $DIR/ignored_unit_patterns.rs:17:13
    |
 LL |         Err(_) => {},
    |             ^ help: use `()` instead of `_`: `()`
 
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:14:15
+  --> $DIR/ignored_unit_patterns.rs:19:15
    |
 LL |     if let Ok(_) = foo() {}
    |               ^ help: use `()` instead of `_`: `()`
 
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:16:28
+  --> $DIR/ignored_unit_patterns.rs:21:28
    |
 LL |     let _ = foo().map_err(|_| todo!());
    |                            ^ help: use `()` instead of `_`: `()`
 
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:22:16
+  --> $DIR/ignored_unit_patterns.rs:27:16
    |
 LL |             Ok(_) => {},
    |                ^ help: use `()` instead of `_`: `()`
 
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:24:17
+  --> $DIR/ignored_unit_patterns.rs:29:17
    |
 LL |             Err(_) => {},
    |                 ^ help: use `()` instead of `_`: `()`
 
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:36:9
+  --> $DIR/ignored_unit_patterns.rs:41:9
    |
 LL |     let _ = foo().unwrap();
    |         ^ help: use `()` instead of `_`: `()`
 
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:45:13
+  --> $DIR/ignored_unit_patterns.rs:50:13
    |
 LL |         (1, _) => unimplemented!(),
    |             ^ help: use `()` instead of `_`: `()`
 
 error: matching over `()` is more explicit
-  --> $DIR/ignored_unit_patterns.rs:52:13
+  --> $DIR/ignored_unit_patterns.rs:57:13
    |
 LL |     for (x, _) in v {
    |             ^ help: use `()` instead of `_`: `()`

tests/ui/needless_borrow.fixed

@@ -131,6 +131,9 @@ fn main() {
             0
         }
     }
+
+    // issue #11786
+    let x: (&str,) = ("",);
 }
 
 #[allow(clippy::needless_borrowed_reference)]

tests/ui/needless_borrow.rs

@@ -131,6 +131,9 @@ fn main() {
             0
         }
     }
+
+    // issue #11786
+    let x: (&str,) = (&"",);
 }
 
 #[allow(clippy::needless_borrowed_reference)]

tests/ui/needless_borrow.stderr

@@ -121,41 +121,47 @@ error: this expression creates a reference which is immediately dereferenced by
 LL |     (&&5).foo();
    |     ^^^^^ help: change this to: `(&5)`
 
+error: this expression creates a reference which is immediately dereferenced by the compiler
+  --> $DIR/needless_borrow.rs:136:23
+   |
+LL |     let x: (&str,) = (&"",);
+   |                       ^^^ help: change this to: `""`
+
 error: this expression borrows a value the compiler would automatically borrow
-  --> $DIR/needless_borrow.rs:175:13
+  --> $DIR/needless_borrow.rs:178:13
    |
 LL |             (&self.f)()
    |             ^^^^^^^^^ help: change this to: `(self.f)`
 
 error: this expression borrows a value the compiler would automatically borrow
-  --> $DIR/needless_borrow.rs:184:13
+  --> $DIR/needless_borrow.rs:187:13
    |
 LL |             (&mut self.f)()
    |             ^^^^^^^^^^^^^ help: change this to: `(self.f)`
 
 error: this expression borrows a value the compiler would automatically borrow
-  --> $DIR/needless_borrow.rs:221:22
+  --> $DIR/needless_borrow.rs:224:22
    |
 LL |         let _ = &mut (&mut { x.u }).x;
    |                      ^^^^^^^^^^^^^^ help: change this to: `{ x.u }`
 
 error: this expression borrows a value the compiler would automatically borrow
-  --> $DIR/needless_borrow.rs:228:22
+  --> $DIR/needless_borrow.rs:231:22
    |
 LL |         let _ = &mut (&mut { x.u }).x;
    |                      ^^^^^^^^^^^^^^ help: change this to: `{ x.u }`
 
 error: this expression borrows a value the compiler would automatically borrow
-  --> $DIR/needless_borrow.rs:232:22
+  --> $DIR/needless_borrow.rs:235:22
    |
 LL |         let _ = &mut (&mut x.u).x;
    |                      ^^^^^^^^^^ help: change this to: `x.u`
 
 error: this expression borrows a value the compiler would automatically borrow
-  --> $DIR/needless_borrow.rs:233:22
+  --> $DIR/needless_borrow.rs:236:22
    |
 LL |         let _ = &mut (&mut { x.u }).x;
    |                      ^^^^^^^^^^^^^^ help: change this to: `{ x.u }`
 
-error: aborting due to 26 previous errors
+error: aborting due to 27 previous errors