Rollup merge of #134244 - Enselic:no-mut-hint-for-raw-ref, r=jieyouxu

rustc_borrowck: Stop suggesting the invalid syntax `&mut raw const`

A legitimate suggestion would be to change from

    &raw const val

to

    &raw mut val

But until we have figured out how to make that happen we should at least
stop suggesting invalid syntax.

I recommend review commit-by-commit.

Part of #127562

Author: matthiaskrgr

Diff for: compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -1100,12 +1100,12 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         }
         let decl_span = local_decl.source_info.span;
 
-        let label = match *local_decl.local_info() {
+        let amp_mut_sugg = match *local_decl.local_info() {
             LocalInfo::User(mir::BindingForm::ImplicitSelf(_)) => {
                 let suggestion = suggest_ampmut_self(self.infcx.tcx, decl_span);
                 let additional =
                     local_trait.map(|span| (span, suggest_ampmut_self(self.infcx.tcx, span)));
-                Some((true, decl_span, suggestion, additional))
+                Some(AmpMutSugg { has_sugg: true, span: decl_span, suggestion, additional })
             }
 
             LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
@@ -1150,7 +1150,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         None
                     }
                     None => {
-                        let (has_sugg, decl_span, sugg) = if name != kw::SelfLower {
+                        if name != kw::SelfLower {
                             suggest_ampmut(
                                 self.infcx.tcx,
                                 local_decl.ty,
@@ -1165,7 +1165,12 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                                     ..
                                 })) => {
                                     let sugg = suggest_ampmut_self(self.infcx.tcx, decl_span);
-                                    (true, decl_span, sugg)
+                                    Some(AmpMutSugg {
+                                        has_sugg: true,
+                                        span: decl_span,
+                                        suggestion: sugg,
+                                        additional: None,
+                                    })
                                 }
                                 // explicit self (eg `self: &'a Self`)
                                 _ => suggest_ampmut(
@@ -1176,8 +1181,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                                     opt_ty_info,
                                 ),
                             }
-                        };
-                        Some((has_sugg, decl_span, sugg, None))
+                        }
                     }
                 }
             }
@@ -1187,15 +1191,24 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 ..
             })) => {
                 let pattern_span: Span = local_decl.source_info.span;
-                suggest_ref_mut(self.infcx.tcx, pattern_span)
-                    .map(|span| (true, span, "mut ".to_owned(), None))
+                suggest_ref_mut(self.infcx.tcx, pattern_span).map(|span| AmpMutSugg {
+                    has_sugg: true,
+                    span,
+                    suggestion: "mut ".to_owned(),
+                    additional: None,
+                })
             }
 
             _ => unreachable!(),
         };
 
-        match label {
-            Some((true, err_help_span, suggested_code, additional)) => {
+        match amp_mut_sugg {
+            Some(AmpMutSugg {
+                has_sugg: true,
+                span: err_help_span,
+                suggestion: suggested_code,
+                additional,
+            }) => {
                 let mut sugg = vec![(err_help_span, suggested_code)];
                 if let Some(s) = additional {
                     sugg.push(s);
@@ -1217,7 +1230,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     );
                 }
             }
-            Some((false, err_label_span, message, _)) => {
+            Some(AmpMutSugg {
+                has_sugg: false, span: err_label_span, suggestion: message, ..
+            }) => {
                 let def_id = self.body.source.def_id();
                 let hir_id = if let Some(local_def_id) = def_id.as_local()
                     && let Some(body) = self.infcx.tcx.hir().maybe_body_owned_by(local_def_id)
@@ -1422,6 +1437,13 @@ fn suggest_ampmut_self<'tcx>(tcx: TyCtxt<'tcx>, span: Span) -> String {
     }
 }
 
+struct AmpMutSugg {
+    has_sugg: bool,
+    span: Span,
+    suggestion: String,
+    additional: Option<(Span, String)>,
+}
+
 // When we want to suggest a user change a local variable to be a `&mut`, there
 // are three potential "obvious" things to highlight:
 //
@@ -1443,7 +1465,7 @@ fn suggest_ampmut<'tcx>(
     decl_span: Span,
     opt_assignment_rhs_span: Option<Span>,
     opt_ty_info: Option<Span>,
-) -> (bool, Span, String) {
+) -> Option<AmpMutSugg> {
     // if there is a RHS and it starts with a `&` from it, then check if it is
     // mutable, and if not, put suggest putting `mut ` to make it mutable.
     // we don't have to worry about lifetime annotations here because they are
@@ -1456,6 +1478,11 @@ fn suggest_ampmut<'tcx>(
         && let Ok(src) = tcx.sess.source_map().span_to_snippet(assignment_rhs_span)
         && let Some(stripped) = src.strip_prefix('&')
     {
+        let is_raw_ref = stripped.trim_start().starts_with("raw ");
+        // We don't support raw refs yet
+        if is_raw_ref {
+            return None;
+        }
         let is_mut = if let Some(rest) = stripped.trim_start().strip_prefix("mut") {
             match rest.chars().next() {
                 // e.g. `&mut x`
@@ -1479,7 +1506,12 @@ fn suggest_ampmut<'tcx>(
 
             // FIXME(Ezrashaw): returning is bad because we still might want to
             // update the annotated type, see #106857.
-            return (true, span, "mut ".to_owned());
+            return Some(AmpMutSugg {
+                has_sugg: true,
+                span,
+                suggestion: "mut ".to_owned(),
+                additional: None,
+            });
         }
     }
 
@@ -1504,18 +1536,23 @@ fn suggest_ampmut<'tcx>(
         && let Some(ws_pos) = src.find(char::is_whitespace)
     {
         let span = span.with_lo(span.lo() + BytePos(ws_pos as u32)).shrink_to_lo();
-        (true, span, " mut".to_owned())
+        Some(AmpMutSugg { has_sugg: true, span, suggestion: " mut".to_owned(), additional: None })
     // if there is already a binding, we modify it to be `mut`
     } else if binding_exists {
         // shrink the span to just after the `&` in `&variable`
         let span = span.with_lo(span.lo() + BytePos(1)).shrink_to_lo();
-        (true, span, "mut ".to_owned())
+        Some(AmpMutSugg { has_sugg: true, span, suggestion: "mut ".to_owned(), additional: None })
     } else {
         // otherwise, suggest that the user annotates the binding; we provide the
         // type of the local.
         let ty = decl_ty.builtin_deref(true).unwrap();
 
-        (false, span, format!("{}mut {}", if decl_ty.is_ref() { "&" } else { "*" }, ty))
+        Some(AmpMutSugg {
+            has_sugg: false,
+            span,
+            suggestion: format!("{}mut {}", if decl_ty.is_ref() { "&" } else { "*" }, ty),
+            additional: None,
+        })
     }
 }
 

Diff for: tests/ui/borrowck/no-invalid-mut-suggestion-for-raw-pointer-issue-127562.rs

@@ -0,0 +1,8 @@
+//! Regression test for invalid suggestion for `&raw const expr` reported in
+//! <https://github.com/rust-lang/rust/issues/127562>.
+
+fn main() {
+    let val = 2;
+    let ptr = &raw const val;
+    unsafe { *ptr = 3; } //~ ERROR cannot assign to `*ptr`, which is behind a `*const` pointer
+}

Diff for: tests/ui/borrowck/no-invalid-mut-suggestion-for-raw-pointer-issue-127562.stderr

@@ -0,0 +1,9 @@
+error[E0594]: cannot assign to `*ptr`, which is behind a `*const` pointer
+  --> $DIR/no-invalid-mut-suggestion-for-raw-pointer-issue-127562.rs:7:14
+   |
+LL |     unsafe { *ptr = 3; }
+   |              ^^^^^^^^ `ptr` is a `*const` pointer, so the data it refers to cannot be written
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0594`.