3 files changed, 81 insertions, 28 deletions

diff --git a/tests/ui/closures/closure-capture-after-clone.rs b/tests/ui/closures/closure-capture-after-clone.rs
index 6e07895f1d3..29fba147909 100644
--- a/tests/ui/closures/closure-capture-after-clone.rs
+++ b/tests/ui/closures/closure-capture-after-clone.rs
@@ -1,13 +1,39 @@
-//@ run-pass
+//! Regression test for issue #1399
+//!
+//! This tests that when a variable is used (via clone) and then later
+//! captured by a closure, the last-use analysis doesn't incorrectly optimize
+//! the earlier use as a "last use" and perform an invalid move.
+//!
+//! The sequence being tested:
+//! 1. Create variable `k`
+//! 2. Use `k.clone()` for some purpose
+//! 3. Later capture `k` in a closure
+//!
+//! The analysis must not treat step 2 as the "last use" since step 3 needs `k`.
+//!
+//! See: https://github.com/rust-lang/rust/issues/1399
 
-#![allow(dead_code)]
-// Make sure #1399 stays fixed
+//@ run-pass
 
-struct A { a: Box<isize> }
+struct A {
+    _a: Box<isize>,
+}
 
 pub fn main() {
-    fn invoke<F>(f: F) where F: FnOnce() { f(); }
+    fn invoke<F>(f: F)
+    where
+        F: FnOnce(),
+    {
+        f();
+    }
+
     let k: Box<_> = 22.into();
-    let _u = A {a: k.clone()};
-    invoke(|| println!("{}", k.clone()) )
+
+    // This clone should NOT be treated as "last use" of k
+    // even though k is not used again until the closure
+    let _u = A { _a: k.clone() };
+
+    // Here k is actually captured by the closure
+    // The last-use analyzer must have accounted for this when processing the clone above
+    invoke(|| println!("{}", k.clone()));
 }
diff --git a/tests/ui/closures/closure-last-use-move.rs b/tests/ui/closures/closure-last-use-move.rs
index 4a166b97bda..f5b99d87f09 100644
--- a/tests/ui/closures/closure-last-use-move.rs
+++ b/tests/ui/closures/closure-last-use-move.rs
@@ -1,21 +1,33 @@
-//@ run-pass
-
-#![allow(dead_code)]
-#![allow(unused_parens)]
-// Issue #1818
+//! Regression test for issue #1818
+//! last-use analysis in closures should allow moves instead of requiring copies.
+//!
+//! The original issue was that the compiler incorrectly flagged certain return values
+//! in anonymous functions/closures as requiring copies of non-copyable values, when
+//! they should have been treated as moves (since they were the last use of the value).
+//!
+//! See: https://github.com/rust-lang/rust/issues/1818
 
+//@ run-pass
 
-fn lp<T, F>(s: String, mut f: F) -> T where F: FnMut(String) -> T {
-    while false {
-        let r = f(s);
-        return (r);
+fn apply<T, F>(s: String, mut f: F) -> T
+where
+    F: FnMut(String) -> T
+{
+    fn g<T, F>(s: String, mut f: F) -> T
+    where
+        F: FnMut(String) -> T
+    {
+        f(s)
     }
-    panic!();
-}
 
-fn apply<T, F>(s: String, mut f: F) -> T where F: FnMut(String) -> T {
-    fn g<T, F>(s: String, mut f: F) -> T where F: FnMut(String) -> T {f(s)}
-    g(s, |v| { let r = f(v); r })
+    g(s, |v| {
+        let r = f(v);
+        r // This should be a move, not requiring copy
+    })
 }
 
-pub fn main() {}
+pub fn main() {
+    // Actually test the functionality
+    let result = apply(String::from("test"), |s| s.len());
+    assert_eq!(result, 4);
+}
diff --git a/tests/ui/closures/closure-upvar-last-use-analysis.rs b/tests/ui/closures/closure-upvar-last-use-analysis.rs
index 23c263c9805..2c3e349437d 100644
--- a/tests/ui/closures/closure-upvar-last-use-analysis.rs
+++ b/tests/ui/closures/closure-upvar-last-use-analysis.rs
@@ -1,14 +1,29 @@
-//@ run-pass
+//! Regression test for issue #1399
+//!
+//! This tests that the compiler's last-use analysis correctly handles variables
+//! that are captured by closures (upvars). The original issue was that the analysis
+//! would incorrectly optimize variable usage as "last use" and perform moves, even when
+//! the variable was later needed by a closure that captured it.
+//!
+//! See: https://github.com/rust-lang/rust/issues/1399
 
-#![allow(dead_code)]
-// Make sure #1399 stays fixed
+//@ run-pass
 
-struct A { a: Box<isize> }
+struct A {
+    _a: Box<isize>,
+}
 
 fn foo() -> Box<dyn FnMut() -> isize + 'static> {
     let k: Box<_> = Box::new(22);
-    let _u = A {a: k.clone()};
-    let result  = || 22;
+
+    // This use of k.clone() should not be treated as a "last use"
+    // even though the closure below doesn't actually capture k
+    let _u = A { _a: k.clone() };
+
+    // The closure doesn't actually use k, but the analyzer needs to handle
+    // the potential capture scenario correctly
+    let result = || 22;
+
     Box::new(result)
 }