Rollup merge of rust-lang#140580 - jdonszelmann:variables-external-macros, r=m-ou-se

Don't name variables from external macros in borrow errors.

This came up as part of the expansion of format_args. However, it's a more general problem (and now solution).

I noticed that this does change another test, moving out of fields in derives on packed struct. However, I think this is a better error simply because it used to refer to `other.0` which is an implementation detail which doesn't really make sense.

cc `@m-ou-se`

Author: Zalathar

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -2954,12 +2954,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             }
         }
 
-        let name = if borrow_span.in_external_macro(self.infcx.tcx.sess.source_map()) {
-            // Don't name local variables in external macros.
-            "value".to_string()
-        } else {
-            format!("`{name}`")
-        };
+        let name = format!("`{name}`");
 
         let mut err = self.path_does_not_live_long_enough(borrow_span, &name);
 

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -317,6 +317,14 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         opt: DescribePlaceOpt,
     ) -> Option<String> {
         let local = place.local;
+        if self.body.local_decls[local]
+            .source_info
+            .span
+            .in_external_macro(self.infcx.tcx.sess.source_map())
+        {
+            return None;
+        }
+
         let mut autoderef_index = None;
         let mut buf = String::new();
         let mut ok = self.append_local_to_string(local, &mut buf);

tests/ui/derives/deriving-with-repr-packed-move-errors.rs

@@ -11,15 +11,15 @@ use std::cmp::Ordering;
 #[repr(packed)]
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
 struct StructA(String);
-//~^ ERROR: cannot move out of `self` which is behind a shared reference
-//~| ERROR: cannot move out of `self` which is behind a shared reference
-//~| ERROR: cannot move out of `other` which is behind a shared reference
-//~| ERROR: cannot move out of `self` which is behind a shared reference
-//~| ERROR: cannot move out of `other` which is behind a shared reference
-//~| ERROR: cannot move out of `self` which is behind a shared reference
-//~| ERROR: cannot move out of `other` which is behind a shared reference
-//~| ERROR: cannot move out of `self` which is behind a shared reference
-//~| ERROR: cannot move out of `self` which is behind a shared reference
+//~^ ERROR: cannot move out of a shared reference [E0507]
+//~| ERROR: cannot move out of a shared reference [E0507]
+//~| ERROR: cannot move out of a shared reference [E0507]
+//~| ERROR: cannot move out of a shared reference [E0507]
+//~| ERROR: cannot move out of a shared reference [E0507]
+//~| ERROR: cannot move out of a shared reference [E0507]
+//~| ERROR: cannot move out of a shared reference [E0507]
+//~| ERROR: cannot move out of a shared reference [E0507]
+//~| ERROR: cannot move out of a shared reference [E0507]
 
 
 // Unrelated impl: additinal diagnostic should NOT be emitted

tests/ui/derives/deriving-with-repr-packed-move-errors.stderr

@@ -1,122 +1,125 @@
-error[E0507]: cannot move out of `self` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |          ----- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `self.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
 help: consider cloning the value if the performance cost is acceptable
    |
 LL | struct StructA(String.clone());
    |                      ++++++++
 
-error[E0507]: cannot move out of `self` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |                 --------- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `self.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(PartialEq)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
 help: consider cloning the value if the performance cost is acceptable
    |
 LL | struct StructA(String.clone());
    |                      ++++++++
 
-error[E0507]: cannot move out of `other` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |                 --------- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `other.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(PartialEq)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 help: consider cloning the value if the performance cost is acceptable
    |
 LL | struct StructA(String.clone());
    |                      ++++++++
 
-error[E0507]: cannot move out of `self` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |                                ---------- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `self.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(PartialOrd)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
 help: consider cloning the value if the performance cost is acceptable
    |
 LL | struct StructA(String.clone());
    |                      ++++++++
 
-error[E0507]: cannot move out of `other` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |                                ---------- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `other.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(PartialOrd)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 help: consider cloning the value if the performance cost is acceptable
    |
 LL | struct StructA(String.clone());
    |                      ++++++++
 
-error[E0507]: cannot move out of `self` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |                                            --- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `self.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Ord)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
 help: consider cloning the value if the performance cost is acceptable
    |
 LL | struct StructA(String.clone());
    |                      ++++++++
 
-error[E0507]: cannot move out of `other` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |                                            --- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `other.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Ord)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 help: consider cloning the value if the performance cost is acceptable
    |
 LL | struct StructA(String.clone());
    |                      ++++++++
 
-error[E0507]: cannot move out of `self` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |                                                 ---- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `self.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Hash)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
 help: consider cloning the value if the performance cost is acceptable
    |
 LL | struct StructA(String.clone());
    |                      ++++++++
 
-error[E0507]: cannot move out of `self` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed-move-errors.rs:13:16
    |
 LL | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
    |                                                       ----- in this derive macro expansion
 LL | struct StructA(String);
-   |                ^^^^^^ move occurs because `self.0` has type `String`, which does not implement the `Copy` trait
+   |                ^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Clone)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
 help: consider cloning the value if the performance cost is acceptable

tests/ui/derives/deriving-with-repr-packed.rs

@@ -20,7 +20,7 @@ struct Y(usize);
 #[derive(Debug, Default)]
 #[repr(packed)]
 struct X(Y);
-//~^ ERROR cannot move out of `self` which is behind a shared reference
+//~^ ERROR cannot move out of a shared reference [E0507]
 
 #[derive(Debug)]
 #[repr(packed)]

tests/ui/derives/deriving-with-repr-packed.stderr

@@ -1,11 +1,11 @@
-error[E0507]: cannot move out of `self` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed.rs:22:10
    |
 LL | #[derive(Debug, Default)]
    |          ----- in this derive macro expansion
 LL | #[repr(packed)]
 LL | struct X(Y);
-   |          ^ move occurs because `self.0` has type `Y`, which does not implement the `Copy` trait
+   |          ^ move occurs because value has type `Y`, which does not implement the `Copy` trait
    |
 note: if `Y` implemented `Clone`, you could clone the value
   --> $DIR/deriving-with-repr-packed.rs:16:1
@@ -23,14 +23,14 @@ error[E0161]: cannot move a value of type `[u8]`
 LL |     data: [u8],
    |     ^^^^^^^^^^ the size of `[u8]` cannot be statically determined
 
-error[E0507]: cannot move out of `self.data` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed.rs:29:5
    |
 LL | #[derive(Debug)]
    |          ----- in this derive macro expansion
 ...
 LL |     data: [u8],
-   |     ^^^^^^^^^^ move occurs because `self.data` has type `[u8]`, which does not implement the `Copy` trait
+   |     ^^^^^^^^^^ move occurs because value has type `[u8]`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
 
@@ -40,14 +40,14 @@ error[E0161]: cannot move a value of type `str`
 LL |     data: str,
    |     ^^^^^^^^^ the size of `str` cannot be statically determined
 
-error[E0507]: cannot move out of `self.data` which is behind a shared reference
+error[E0507]: cannot move out of a shared reference
   --> $DIR/deriving-with-repr-packed.rs:38:5
    |
 LL | #[derive(Debug)]
    |          ----- in this derive macro expansion
 ...
 LL |     data: str,
-   |     ^^^^^^^^^ move occurs because `self.data` has type `str`, which does not implement the `Copy` trait
+   |     ^^^^^^^^^ move occurs because value has type `str`, which does not implement the `Copy` trait
    |
    = note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
 

tests/ui/macros/auxiliary/return_from_external_macro.rs

@@ -0,0 +1,11 @@
+#![feature(super_let)]
+
+#[macro_export]
+macro_rules! foo {
+    () => {
+        {
+            super let args = 1;
+            &args
+        }
+    };
+}

tests/ui/macros/return_from_external_macro.rs

@@ -0,0 +1,17 @@
+//@ aux-crate: ret_from_ext=return_from_external_macro.rs
+
+#![feature(super_let)]
+extern crate ret_from_ext;
+
+fn foo() -> impl Sized {
+    drop(|| ret_from_ext::foo!());
+    //~^ ERROR cannot return reference to local binding
+
+    ret_from_ext::foo!()
+    //~^ ERROR temporary value dropped while borrowed
+}
+//~^ NOTE temporary value is freed at the end of this statement
+
+fn main() {
+    foo();
+}

tests/ui/macros/return_from_external_macro.stderr

@@ -0,0 +1,29 @@
+error[E0515]: cannot return reference to local binding
+  --> $DIR/return_from_external_macro.rs:7:13
+   |
+LL |     drop(|| ret_from_ext::foo!());
+   |             ^^^^^^^^^^^^^^^^^^^^
+   |             |
+   |             returns a reference to data owned by the current function
+   |             local binding introduced here
+   |
+   = note: this error originates in the macro `ret_from_ext::foo` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0716]: temporary value dropped while borrowed
+  --> $DIR/return_from_external_macro.rs:10:5
+   |
+LL |     ret_from_ext::foo!()
+   |     ^^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     creates a temporary value which is freed while still in use
+   |     opaque type requires that borrow lasts for `'static`
+LL |
+LL | }
+   | - temporary value is freed at the end of this statement
+   |
+   = note: this error originates in the macro `ret_from_ext::foo` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0515, E0716.
+For more information about an error, try `rustc --explain E0515`.

tests/ui/pin-macro/lifetime_errors_on_promotion_misusage.rs

@@ -9,14 +9,14 @@ use core::{
 
 fn function_call_stops_borrow_extension() {
     let phantom_pinned = identity(pin!(PhantomPinned));
-    //~^ ERROR does not live long enough
+    //~^ ERROR temporary value dropped while borrowed [E0716]
     stuff(phantom_pinned)
 }
 
 fn promotion_only_works_for_the_innermost_block() {
     let phantom_pinned = {
         let phantom_pinned = pin!(PhantomPinned);
-        //~^ ERROR does not live long enough
+        //~^ ERROR temporary value dropped while borrowed [E0716]
         phantom_pinned
     };
     stuff(phantom_pinned)

tests/ui/pin-macro/lifetime_errors_on_promotion_misusage.stderr

@@ -1,29 +1,31 @@
-error[E0597]: value does not live long enough
+error[E0716]: temporary value dropped while borrowed
   --> $DIR/lifetime_errors_on_promotion_misusage.rs:11:35
    |
 LL |     let phantom_pinned = identity(pin!(PhantomPinned));
-   |                                   ^^^^^^^^^^^^^^^^^^^ - value dropped here while still borrowed
+   |                                   ^^^^^^^^^^^^^^^^^^^ - temporary value is freed at the end of this statement
    |                                   |
-   |                                   borrowed value does not live long enough
+   |                                   creates a temporary value which is freed while still in use
 LL |
 LL |     stuff(phantom_pinned)
    |           -------------- borrow later used here
    |
+   = note: consider using a `let` binding to create a longer lived value
    = note: this error originates in the macro `pin` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0597]: value does not live long enough
+error[E0716]: temporary value dropped while borrowed
   --> $DIR/lifetime_errors_on_promotion_misusage.rs:18:30
    |
 LL |     let phantom_pinned = {
    |         -------------- borrow later stored here
 LL |         let phantom_pinned = pin!(PhantomPinned);
-   |                              ^^^^^^^^^^^^^^^^^^^ borrowed value does not live long enough
+   |                              ^^^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
 ...
 LL |     };
-   |     - value dropped here while still borrowed
+   |     - temporary value is freed at the end of this statement
    |
+   = note: consider using a `let` binding to create a longer lived value
    = note: this error originates in the macro `pin` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0597`.
+For more information about this error, try `rustc --explain E0716`.