detect when suggested paths enter extern crates more rigorously

src/test/ui/resolve/auxiliary/issue-80079.rs

@@ -0,0 +1,18 @@
+#![crate_type = "lib"]
+
+pub mod public {
+    use private_import;
+
+    // should not be suggested since it is private
+    struct Foo;
+
+    mod private_module {
+        // should not be suggested since it is private
+        pub struct Foo;
+    }
+}
+
+mod private_import {
+    // should not be suggested since it is private
+    pub struct Foo;
+}

src/test/ui/resolve/issue-80079.rs

@@ -0,0 +1,12 @@
+// aux-build:issue-80079.rs
+
+// using a module from another crate should not cause errors to suggest private
+// items in that module
+
+extern crate issue_80079;
+
+use issue_80079::public;
+
+fn main() {
+    let _ = Foo; //~ ERROR cannot find value `Foo` in this scope
+}

src/test/ui/resolve/issue-80079.stderr

@@ -0,0 +1,9 @@
+error[E0425]: cannot find value `Foo` in this scope
+  --> $DIR/issue-80079.rs:11:13
+   |
+LL |     let _ = Foo;
+   |             ^^^ not found in this scope
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0425`.