Add test checking various assignments are accepted in Polonius

Author: lqd

src/test/ui/nll/polonius/assignment-kills-loans.rs

@@ -0,0 +1,88 @@
+#![allow(dead_code)]
+
+// This tests the various kinds of assignments there are. Polonius used to generate `killed`
+// facts only on simple assigments, but not projections, incorrectly causing errors to be emitted
+// for code accepted by NLL. They are all variations from example code in the NLL RFC.
+
+// check-pass
+// compile-flags: -Z borrowck=mir -Z polonius
+// ignore-compare-mode-nll
+
+struct List<T> {
+    value: T,
+    next: Option<Box<List<T>>>,
+}
+
+// Assignment to a local: the `list` assignment should clear the existing
+// borrows of `list.value` and `list.next`
+fn assignment_to_local<T>(mut list: &mut List<T>) -> Vec<&mut T> {
+    let mut result = vec![];
+    loop {
+        result.push(&mut list.value);
+        if let Some(n) = list.next.as_mut() {
+            list = n;
+        } else {
+            return result;
+        }
+    }
+}
+
+// Assignment to a deref projection: the `*list` assignment should clear the existing
+// borrows of `list.value` and `list.next`
+fn assignment_to_deref_projection<T>(mut list: Box<&mut List<T>>) -> Vec<&mut T> {
+    let mut result = vec![];
+    loop {
+        result.push(&mut list.value);
+        if let Some(n) = list.next.as_mut() {
+            *list = n;
+        } else {
+            return result;
+        }
+    }
+}
+
+// Assignment to a field projection: the `list.0` assignment should clear the existing
+// borrows of `list.0.value` and `list.0.next`
+fn assignment_to_field_projection<T>(mut list: (&mut List<T>,)) -> Vec<&mut T> {
+    let mut result = vec![];
+    loop {
+        result.push(&mut list.0.value);
+        if let Some(n) = list.0.next.as_mut() {
+            list.0 = n;
+        } else {
+            return result;
+        }
+    }
+}
+
+// Assignment to a deref field projection: the `*list.0` assignment should clear the existing
+// borrows of `list.0.value` and `list.0.next`
+fn assignment_to_deref_field_projection<T>(mut list: (Box<&mut List<T>>,)) -> Vec<&mut T> {
+    let mut result = vec![];
+    loop {
+        result.push(&mut list.0.value);
+        if let Some(n) = list.0.next.as_mut() {
+            *list.0 = n;
+        } else {
+            return result;
+        }
+    }
+}
+
+// Similar to `assignment_to_deref_field_projection` but through a longer projection chain
+fn assignment_through_projection_chain<T>(
+    mut list: (((((Box<&mut List<T>>,),),),),),
+) -> Vec<&mut T> {
+    let mut result = vec![];
+    loop {
+        result.push(&mut ((((list.0).0).0).0).0.value);
+        if let Some(n) = ((((list.0).0).0).0).0.next.as_mut() {
+            *((((list.0).0).0).0).0 = n;
+        } else {
+            return result;
+        }
+    }
+}
+
+fn main() {
+}