On function and method calls in patterns, link to the book

```
error: expected a pattern, found an expression
 --> f889.rs:3:13
  |
3 |     let (x, y.drop()) = (1, 2); //~ ERROR
  |             ^^^^^^^^ not a pattern
  |
  = note: arbitrary expressions are not allowed in patterns: <https://doc.rust-lang.org/book/ch18-00-patterns.html>

error[E0532]: expected a pattern, found a function call
 --> f889.rs:2:13
  |
2 |     let (x, drop(y)) = (1, 2); //~ ERROR
  |             ^^^^ not a tuple struct or tuple variant
  |
  = note: function calls are not allowed in patterns: <https://doc.rust-lang.org/book/ch18-00-patterns.html>
```

Fix #97200.

1 files changed, 3 insertions, 1 deletions

diff --git a/tests/ui/sized/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.stderr b/tests/ui/sized/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.stderr
index fc431eb1412..d40e9822435 100644
--- a/tests/ui/sized/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.stderr
+++ b/tests/ui/sized/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.stderr
@@ -2,7 +2,9 @@ error: expected a pattern, found an expression
   --> $DIR/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.rs:2:31
    |
 LL |     let str::<{fn str() { let str::T>>::as_bytes; }}, T>::as_bytes;
-   |                               ^^^^^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
+   |                               ^^^^^^^^^^^^^^^^^^ not a pattern
+   |
+   = note: arbitrary expressions are not allowed in patterns: <https://doc.rust-lang.org/book/ch18-00-patterns.html>
 
 error[E0412]: cannot find type `T` in this scope
   --> $DIR/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.rs:2:55