Don't suggest changing a method inside a expansion

Author: Urgau

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1723,8 +1723,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Don't emit a suggestion if we found an actual method
             // that had unsatisfied trait bounds
             if unsatisfied_predicates.is_empty()
-                // ...or if we already suggested that name because of `rustc_confusable` annotation.
+                // ...or if we already suggested that name because of `rustc_confusable` annotation
                 && Some(similar_candidate.name()) != confusable_suggested
+                // and if the we aren't in an expansion.
+                && !span.from_expansion()
             {
                 self.find_likely_intended_associated_item(
                     &mut err,

tests/ui/macros/missing-writer-issue-139830.rs

@@ -0,0 +1,7 @@
+// Make sure we don't suggest a method change inside the `write!` macro.
+
+fn main() {
+    let mut buf = String::new();
+    let _ = write!(buf, "foo");
+    //~^ ERROR cannot write into `String`
+}

tests/ui/macros/missing-writer-issue-139830.stderr

@@ -0,0 +1,23 @@
+error[E0599]: cannot write into `String`
+  --> $DIR/missing-writer-issue-139830.rs:5:20
+   |
+LL |     let _ = write!(buf, "foo");
+   |                    ^^^
+  --> $SRC_DIR/core/src/fmt/mod.rs:LL:COL
+   |
+   = note: the method is available for `String` here
+   |
+note: must implement `io::Write`, `fmt::Write`, or have a `write_fmt` method
+  --> $DIR/missing-writer-issue-139830.rs:5:20
+   |
+LL |     let _ = write!(buf, "foo");
+   |                    ^^^
+   = help: items from traits can only be used if the trait is in scope
+help: trait `Write` which provides `write_fmt` is implemented but not in scope; perhaps you want to import it
+   |
+LL + use std::fmt::Write;
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0599`.