Rollup merge of #139921 - Kivooeo:master, r=WaffleLapkin

improve diagnostic for raw pointer field access with ->

This PR enhances the error messages emitted by the Rust compiler when users attempt to use the `->` operator for field access on raw pointers or when dereferencing is needed. The changes aim to provide clearer guidance, by suggesting the correct use of the `.` operator and explicit dereferencing.

**Before:**
```
help: `xs` is a raw pointer; try dereferencing it
   |
LL |         (*xs)->count += 1;
   |         ++  +
```

**Now:**
```
help: use `.` on a dereferenced raw pointer instead
   |
LL -         xs->count += 1;
LL +         (*xs).count += 1;
   |
```

I added extra clarification in the message. Since this error occurs in the parser, we can't be certain that the type is a raw pointer. That's why the message includes only a small note in brackets. (In contrast, the message above is emitted in HIR, where we *can* check whether it's a raw pointer.)

**Before:**
```
  --> main.rs:11:11
   |
11 |         xs->count += 1;
   |           ^^
   |
   = help: the . operator will dereference the value if needed
```
**After:**
```
--> main.rs:11:11
   |
11 |         xs->count += 1;
   |           ^^
   |
   = help: the `.` operator will automatically dereference the value, except if the value is a raw pointer
```

2 files changed, 3 insertions, 3 deletions

diff --git a/tests/ui/parser/issues/issue-118530-ice.rs b/tests/ui/parser/issues/issue-118530-ice.rs
index cf14eebec2b..8930eb86c6b 100644
--- a/tests/ui/parser/issues/issue-118530-ice.rs
+++ b/tests/ui/parser/issues/issue-118530-ice.rs
@@ -5,7 +5,7 @@ fn bar() -> String {
     attr::fn bar() -> String { //~ ERROR expected identifier, found keyword `fn`
     //~^ ERROR expected one of `(`, `.`, `::`, `;`, `?`, `}`, or an operator, found `{`
     //~| ERROR expected `;`, found `bar`
-    //~| ERROR `->` used for field access or method call
+    //~| ERROR `->` is not valid syntax for field accesses and method calls
     #[attr]
     [1, 2, 3].iter().map().collect::<String>()
     #[attr]
diff --git a/tests/ui/parser/issues/issue-118530-ice.stderr b/tests/ui/parser/issues/issue-118530-ice.stderr
index 72c0397e9c9..ef891d1dc29 100644
--- a/tests/ui/parser/issues/issue-118530-ice.stderr
+++ b/tests/ui/parser/issues/issue-118530-ice.stderr
@@ -33,13 +33,13 @@ LL |     attr::fn bar() -> String {
    |             |
    |             help: add `;` here
 
-error: `->` used for field access or method call
+error: `->` is not valid syntax for field accesses and method calls
   --> $DIR/issue-118530-ice.rs:5:20
    |
 LL |     attr::fn bar() -> String {
    |                    ^^
    |
-   = help: the `.` operator will dereference the value if needed
+   = help: the `.` operator will automatically dereference the value, except if the value is a raw pointer
 help: try using `.` instead
    |
 LL -     attr::fn bar() -> String {