Add qualif smoke tests for const loops

src/test/ui/consts/control-flow/drop-failure.rs

@@ -1,4 +1,5 @@
 #![feature(const_if_match)]
+#![feature(const_loop)]
 
 // `x` is *not* always moved into the final value may be dropped inside the initializer.
 const _: Option<Vec<i32>> = {
@@ -32,4 +33,27 @@ const _: Vec<i32> = {
     }
 };
 
+const _: Option<Vec<i32>> = {
+    let mut some = Some(Vec::new());
+    let mut tmp = None;
+    //~^ ERROR destructors cannot be evaluated at compile-time
+
+    let mut i = 0;
+    while i < 10 {
+        tmp = some;
+        some = None;
+
+        if i > 100 {
+            break;
+        }
+
+        some = tmp;
+        tmp = None;
+
+        i += 1;
+    }
+
+    some
+};
+
 fn main() {}

src/test/ui/consts/control-flow/drop-success.rs

@@ -1,6 +1,7 @@
 // run-pass
 
 #![feature(const_if_match)]
+#![feature(const_loop)]
 
 // `x` is always moved into the final value and is not dropped inside the initializer.
 const _: Option<Vec<i32>> = {
@@ -21,4 +22,24 @@ const _: Option<Vec<i32>> = {
     }
 };
 
+const _: Option<Vec<i32>> = {
+    let mut some = Some(Vec::new());
+    let mut tmp = None;
+
+    let mut i = 0;
+    while i < 10 {
+        tmp = some;
+        some = None;
+
+        // We can never exit the loop with `Some` in `tmp`.
+
+        some = tmp;
+        tmp = None;
+
+        i += 1;
+    }
+
+    some
+};
+
 fn main() {}

src/test/ui/consts/control-flow/interior-mutability.rs

@@ -2,6 +2,7 @@
 // disqualifies it from promotion.
 
 #![feature(const_if_match)]
+#![feature(const_loop)]
 
 use std::cell::Cell;
 
@@ -21,7 +22,22 @@ const Y: Option<Cell<i32>> = {
     y
 };
 
+const Z: Option<Cell<i32>> = {
+    let mut z = None;
+    let mut i = 0;
+    while i < 10 {
+        if i == 8 {
+            z = Some(Cell::new(4));
+        }
+
+        i += 1;
+    }
+    z
+};
+
+
 fn main() {
     let x: &'static _ = &X; //~ ERROR temporary value dropped while borrowed
     let y: &'static _ = &Y; //~ ERROR temporary value dropped while borrowed
+    let z: &'static _ = &Z; //~ ERROR temporary value dropped while borrowed
 }