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

compiler/rustc_parse/src/errors.rs

@@ -3333,7 +3333,6 @@ pub(crate) struct AsyncImpl {
 #[help]
 pub(crate) struct ExprRArrowCall {
     #[primary_span]
-    #[suggestion(style = "verbose", applicability = "machine-applicable", code = ".")]
     pub span: Span,
 }
 

tests/ui/parser/expr-rarrow-call-on-a-raw-pointer.fixed

@@ -0,0 +1,23 @@
+//@ run-rustfix
+#![allow(
+    dead_code,
+    unused_must_use
+)]
+
+struct Named {
+    foo: usize,
+}
+
+struct Unnamed(usize);
+
+unsafe fn named_struct_field_access(named: *mut Named) {
+    (*named).foo += 1; //~ ERROR `->` used for field access or method call
+    //~^ ERROR no field `foo` on type `*mut Named`
+}
+
+unsafe fn unnamed_struct_field_access(unnamed: *mut Unnamed) {
+    (*unnamed).0 += 1; //~ ERROR `->` used for field access or method call
+    //~^ ERROR no field `0` on type `*mut Unnamed`
+}
+
+fn main() {}

tests/ui/parser/expr-rarrow-call-on-a-raw-pointer.rs

@@ -0,0 +1,23 @@
+//@ run-rustfix
+#![allow(
+    dead_code,
+    unused_must_use
+)]
+
+struct Named {
+    foo: usize,
+}
+
+struct Unnamed(usize);
+
+unsafe fn named_struct_field_access(named: *mut Named) {
+    named->foo += 1; //~ ERROR `->` used for field access or method call
+    //~^ ERROR no field `foo` on type `*mut Named`
+}
+
+unsafe fn unnamed_struct_field_access(unnamed: *mut Unnamed) {
+    unnamed->0 += 1; //~ ERROR `->` used for field access or method call
+    //~^ ERROR no field `0` on type `*mut Unnamed`
+}
+
+fn main() {}

tests/ui/parser/expr-rarrow-call-on-a-raw-pointer.stderr

@@ -0,0 +1,43 @@
+error: `->` used for field access or method call
+  --> $DIR/expr-rarrow-call-on-a-raw-pointer.rs:14:10
+   |
+LL |     named->foo += 1;
+   |          ^^
+   |
+   = help: the `.` operator will automatically dereference the value, except if the value is a raw pointer
+
+error: `->` used for field access or method call
+  --> $DIR/expr-rarrow-call-on-a-raw-pointer.rs:19:12
+   |
+LL |     unnamed->0 += 1;
+   |            ^^
+   |
+   = help: the `.` operator will automatically dereference the value, except if the value is a raw pointer
+
+error[E0609]: no field `foo` on type `*mut Named`
+  --> $DIR/expr-rarrow-call-on-a-raw-pointer.rs:14:12
+   |
+LL |     named->foo += 1;
+   |            ^^^ unknown field
+   |
+help: `named` is a raw pointer; try dereferencing it
+   |
+LL -     named->foo += 1;
+LL +     (*named).foo += 1;
+   |
+
+error[E0609]: no field `0` on type `*mut Unnamed`
+  --> $DIR/expr-rarrow-call-on-a-raw-pointer.rs:19:14
+   |
+LL |     unnamed->0 += 1;
+   |              ^ unknown field
+   |
+help: `unnamed` is a raw pointer; try dereferencing it
+   |
+LL -     unnamed->0 += 1;
+LL +     (*unnamed).0 += 1;
+   |
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0609`.

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

@@ -39,12 +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: try using `.` instead
-   |
-LL -     attr::fn bar() -> String {
-LL +     attr::fn bar() . String {
-   |
+   = help: the `.` operator will automatically dereference the value, except if the value is a raw pointer
 
 error: expected one of `(`, `.`, `::`, `;`, `?`, `}`, or an operator, found `{`
   --> $DIR/issue-118530-ice.rs:5:30