improve diagnostic for raw pointer field access using ->

Author: Kivooeo

compiler/rustc_hir_typeck/src/expr.rs

@@ -3289,8 +3289,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err.multipart_suggestion(
             format!("{val} is a raw pointer; try dereferencing it"),
             vec![
-                (base.span.shrink_to_lo(), "(*".to_string()),
-                (base.span.shrink_to_hi(), ")".to_string()),
+                (base.span.shrink_to_lo(), "(*".into()),
+                (base.span.between(field.span), format!(").")),
             ],
             Applicability::MaybeIncorrect,
         );

compiler/rustc_parse/messages.ftl

@@ -248,7 +248,7 @@ parse_expected_trait_in_trait_impl_found_type = expected a trait, found type
 
 parse_expr_rarrow_call = `->` used for field access or method call
     .suggestion = try using `.` instead
-    .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
 
 parse_extern_crate_name_with_dashes = crate name using dashes are not valid in `extern crate` statements
     .label = dash-separated idents are not valid

tests/ui/parser/expr-rarrow-call.stderr

@@ -4,7 +4,7 @@ error: `->` used for field access or method call
 LL |     named->foo;
    |          ^^
    |
-   = 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 -     named->foo;
@@ -17,7 +17,7 @@ error: `->` used for field access or method call
 LL |     unnamed->0;
    |            ^^
    |
-   = 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 -     unnamed->0;
@@ -30,7 +30,7 @@ error: `->` used for field access or method call
 LL |     t->0;
    |      ^^
    |
-   = 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 -     t->0;
@@ -43,7 +43,7 @@ error: `->` used for field access or method call
 LL |     t->1;
    |      ^^
    |
-   = 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 -     t->1;
@@ -56,7 +56,7 @@ error: `->` used for field access or method call
 LL |     foo->clone();
    |        ^^
    |
-   = 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 -     foo->clone();

tests/ui/parser/issues/issue-118530-ice.stderr

@@ -39,7 +39,7 @@ error: `->` used for field access or method call
 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 {

tests/ui/suggestions/parenthesized-deref-suggestion.stderr

@@ -6,8 +6,9 @@ LL |     (sess as *const Session).opts;
    |
 help: the value is a raw pointer; try dereferencing it
    |
-LL |     (*(sess as *const Session)).opts;
-   |     ++                        +
+LL -     (sess as *const Session).opts;
+LL +     (*sess as *const Session).opts;
+   |
 
 error[E0609]: no field `0` on type `[u32; 1]`
   --> $DIR/parenthesized-deref-suggestion.rs:10:21