Do not complain about missing crate named as a keyword

src/librustc_resolve/lib.rs

@@ -3925,8 +3925,11 @@ impl<'a> Resolver<'a> {
                         });
                         if let Some(candidate) = candidates.get(0) {
                             format!("did you mean `{}`?", candidate.path)
-                        } else {
+                        } else if !ident.is_reserved() {
                             format!("maybe a missing `extern crate {};`?", ident)
+                        } else {
+                            // the parser will already have complained about the keyword being used
+                            return PathResult::NonModule(err_path_resolution());
                         }
                     } else if i == 0 {
                         format!("use of undeclared type or module `{}`", ident)

src/librustc_resolve/macros.rs

@@ -929,7 +929,7 @@ impl<'a> Resolver<'a> {
                     let def = path_res.base_def();
                     check_consistency(self, &path, path_span, kind, initial_def, def);
                 }
-                path_res @ PathResult::NonModule(..) | path_res @  PathResult::Failed(..) => {
+                path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed(..) => {
                     let (span, msg) = if let PathResult::Failed(span, msg, ..) = path_res {
                         (span, msg)
                     } else {

src/test/ui/issues/issue-57198-pass.rs

@@ -0,0 +1,9 @@
+// run-pass
+
+mod m {
+    pub fn r#for() {}
+}
+
+fn main() {
+    m::r#for();
+}

src/test/ui/issues/issue-57198.rs

@@ -0,0 +1,8 @@
+mod m {
+    pub fn r#for() {}
+}
+
+fn main() {
+    m::for();
+    //~^ ERROR expected identifier, found keyword `for`
+}

src/test/ui/issues/issue-57198.stderr

@@ -0,0 +1,8 @@
+error: expected identifier, found keyword `for`
+  --> $DIR/issue-57198.rs:6:8
+   |
+LL |     m::for();
+   |        ^^^ expected identifier, found keyword
+
+error: aborting due to previous error
+