add test for super let in non-extending if blocks

Author: dianne

tests/ui/borrowck/super-let-in-if-block.rs

@@ -0,0 +1,29 @@
+//! Test that `super let` bindings in `if` expressions' blocks have the same scope as the result
+//! of the block.
+#![feature(super_let)]
+
+fn main() {
+    // For `super let` in an extending `if`, the binding `temp` should live in the scope of the
+    // outer `let` statement.
+    let x = if true {
+        super let temp = ();
+        &temp
+    } else {
+        super let temp = ();
+        &temp
+    };
+    x;
+
+    // For `super let` in non-extending `if`, the binding `temp` should live in the temporary scope
+    // the `if` expression is in.
+    // TODO: make this not an error
+    std::convert::identity(if true {
+        super let temp = ();
+        &temp
+        //~^ ERROR `temp` does not live long enough
+    } else {
+        super let temp = ();
+        &temp
+        //~^ ERROR `temp` does not live long enough
+    });
+}

tests/ui/borrowck/super-let-in-if-block.stderr

@@ -0,0 +1,30 @@
+error[E0597]: `temp` does not live long enough
+  --> $DIR/super-let-in-if-block.rs:22:9
+   |
+LL |     std::convert::identity(if true {
+   |     ---------------------- borrow later used by call
+LL |         super let temp = ();
+   |                   ---- binding `temp` declared here
+LL |         &temp
+   |         ^^^^^ borrowed value does not live long enough
+LL |
+LL |     } else {
+   |     - `temp` dropped here while still borrowed
+
+error[E0597]: `temp` does not live long enough
+  --> $DIR/super-let-in-if-block.rs:26:9
+   |
+LL |     std::convert::identity(if true {
+   |     ---------------------- borrow later used by call
+...
+LL |         super let temp = ();
+   |                   ---- binding `temp` declared here
+LL |         &temp
+   |         ^^^^^ borrowed value does not live long enough
+LL |
+LL |     });
+   |     - `temp` dropped here while still borrowed
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0597`.