Fix spurious 'value moved here in previous iteration of loop' messages

src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs

@@ -139,7 +139,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
                 let move_msg = if move_spans.for_closure() { " into closure" } else { "" };
 
-                if span == move_span {
+                if location == move_out.source {
                     err.span_label(
                         span,
                         format!("value moved{} here, in previous iteration of loop", move_msg),

src/test/ui/moves/issue-46099-move-in-macro.rs

@@ -0,0 +1,15 @@
+// Regression test for issue #46099
+// Tests that we don't emit spurious
+// 'value moved in previous iteration of loop' message
+
+macro_rules! test {
+    ($v:expr) => {{
+        drop(&$v);
+        $v
+    }}
+}
+
+fn main() {
+    let b = Box::new(true);
+    test!({b}); //~ ERROR use of moved value
+}

src/test/ui/moves/issue-46099-move-in-macro.stderr

@@ -0,0 +1,14 @@
+error[E0382]: use of moved value: `b`
+  --> $DIR/issue-46099-move-in-macro.rs:14:12
+   |
+LL |     let b = Box::new(true);
+   |         - move occurs because `b` has type `std::boxed::Box<bool>`, which does not implement the `Copy` trait
+LL |     test!({b});
+   |            ^
+   |            |
+   |            value moved here
+   |            value used here after move
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0382`.

src/test/ui/moves/move-in-guard-2.stderr

@@ -5,7 +5,10 @@ LL |     let x: Box<_> = box 1;
    |         - move occurs because `x` has type `std::boxed::Box<i32>`, which does not implement the `Copy` trait
 ...
 LL |         (_, 2) if take(x) => (),
-   |                        ^ value moved here, in previous iteration of loop
+   |                        ^
+   |                        |
+   |                        value moved here
+   |                        value used here after move
 
 error: aborting due to previous error