Test the borrowck behavior of if-let guards

Author: LeSeulArtichaut

src/test/ui/borrowck/borrowck-drop-from-guard.rs

@@ -1,3 +1,5 @@
+#![feature(if_let_guard)]
+
 fn foo(_:String) {}
 
 fn main()
@@ -8,4 +10,11 @@ fn main()
  Some(_) => {}
  None => { foo(my_str); } //~ ERROR [E0382]
  }
+
+ let my_str = "hello".to_owned();
+ match Some(42) {
+ Some(_) if let Some(()) = { drop(my_str); None } => {}
+ Some(_) => {}
+ None => { foo(my_str); } //~ ERROR [E0382]
+ }
 }

src/test/ui/borrowck/borrowck-drop-from-guard.stderr

@@ -1,5 +1,5 @@
 error[E0382]: use of moved value: `my_str`
- --> $DIR/borrowck-drop-from-guard.rs:9:23
+ --> $DIR/borrowck-drop-from-guard.rs:11:23
  |
 LL | let my_str = "hello".to_owned();
  | ------ move occurs because `my_str` has type `String`, which does not implement the `Copy` trait
@@ -15,6 +15,23 @@ help: consider cloning the value if the performance cost is acceptable
 LL | Some(_) if { drop(my_str.clone()); false } => {}
  | ++++++++
 
-error: aborting due to previous error
+error[E0382]: use of moved value: `my_str`
+ --> $DIR/borrowck-drop-from-guard.rs:18:23
+ |
+LL | let my_str = "hello".to_owned();
+ | ------ move occurs because `my_str` has type `String`, which does not implement the `Copy` trait
+LL | match Some(42) {
+LL | Some(_) if let Some(()) = { drop(my_str); None } => {}
+ | ------ value moved here
+LL | Some(_) => {}
+LL | None => { foo(my_str); }
+ | ^^^^^^ value used here after move
+ |
+help: consider cloning the value if the performance cost is acceptable
+ |
+LL | Some(_) if let Some(()) = { drop(my_str.clone()); None } => {}
+ | ++++++++
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0382`.

src/test/ui/borrowck/borrowck-mutate-in-guard.rs

@@ -1,9 +1,11 @@
+#![feature(if_let_guard)]
+
 enum Enum<'a> {
  A(&'a isize),
  B(bool),
 }
 
-fn foo() -> isize {
+fn if_guard() -> isize {
  let mut n = 42;
  let mut x = Enum::A(&mut n);
  match x {
@@ -16,6 +18,17 @@ fn foo() -> isize {
  }
 }
 
-fn main() {
- foo();
+fn if_let_guard() -> isize {
+ let mut n = 42;
+ let mut x = Enum::A(&mut n);
+ match x {
+ Enum::A(_) if let Some(()) = { x = Enum::B(false); None } => 1,
+ //~^ ERROR cannot assign `x` in match guard
+ Enum::A(_) if let Some(()) = { let y = &mut x; *y = Enum::B(false); None } => 1,
+ //~^ ERROR cannot mutably borrow `x` in match guard
+ Enum::A(p) => *p,
+ Enum::B(_) => 2,
+ }
 }
+
+fn main() {}

src/test/ui/borrowck/borrowck-mutate-in-guard.stderr

@@ -1,20 +1,37 @@
 error[E0510]: cannot assign `x` in match guard
- --> $DIR/borrowck-mutate-in-guard.rs:10:25
+ --> $DIR/borrowck-mutate-in-guard.rs:12:25
  |
 LL | match x {
  | - value is immutable in match guard
 LL | Enum::A(_) if { x = Enum::B(false); false } => 1,
  | ^^^^^^^^^^^^^^^^^^ cannot assign
 
 error[E0510]: cannot mutably borrow `x` in match guard
- --> $DIR/borrowck-mutate-in-guard.rs:12:33
+ --> $DIR/borrowck-mutate-in-guard.rs:14:33
  |
 LL | match x {
  | - value is immutable in match guard
 ...
 LL | Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
  | ^^^^^^ cannot mutably borrow
 
-error: aborting due to 2 previous errors
+error[E0510]: cannot assign `x` in match guard
+ --> $DIR/borrowck-mutate-in-guard.rs:25:40
+ |
+LL | match x {
+ | - value is immutable in match guard
+LL | Enum::A(_) if let Some(()) = { x = Enum::B(false); None } => 1,
+ | ^^^^^^^^^^^^^^^^^^ cannot assign
+
+error[E0510]: cannot mutably borrow `x` in match guard
+ --> $DIR/borrowck-mutate-in-guard.rs:27:48
+ |
+LL | match x {
+ | - value is immutable in match guard
+...
+LL | Enum::A(_) if let Some(()) = { let y = &mut x; *y = Enum::B(false); None } => 1,
+ | ^^^^^^ cannot mutably borrow
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0510`.

src/test/ui/borrowck/issue-31287-drop-in-guard.rs

@@ -1,8 +1,15 @@
+#![feature(if_let_guard)]
+
 fn main() {
  let a = Some("...".to_owned());
  let b = match a {
  Some(_) if { drop(a); false } => None,
  x => x, //~ ERROR use of moved value: `a`
  };
- println!("{:?}", b);
+
+ let a = Some("...".to_owned());
+ let b = match a {
+ Some(_) if let Some(()) = { drop(a); None } => None,
+ x => x, //~ ERROR use of moved value: `a`
+ };
 }

src/test/ui/borrowck/issue-31287-drop-in-guard.stderr

@@ -1,5 +1,5 @@
 error[E0382]: use of moved value: `a`
- --> $DIR/issue-31287-drop-in-guard.rs:5:9
+ --> $DIR/issue-31287-drop-in-guard.rs:7:9
  |
 LL | let a = Some("...".to_owned());
  | - move occurs because `a` has type `Option<String>`, which does not implement the `Copy` trait
@@ -14,6 +14,22 @@ help: consider cloning the value if the performance cost is acceptable
 LL | Some(_) if { drop(a.clone()); false } => None,
  | ++++++++
 
-error: aborting due to previous error
+error[E0382]: use of moved value: `a`
+ --> $DIR/issue-31287-drop-in-guard.rs:13:9
+ |
+LL | let a = Some("...".to_owned());
+ | - move occurs because `a` has type `Option<String>`, which does not implement the `Copy` trait
+LL | let b = match a {
+LL | Some(_) if let Some(()) = { drop(a); None } => None,
+ | - value moved here
+LL | x => x,
+ | ^ value used here after move
+ |
+help: consider cloning the value if the performance cost is acceptable
+ |
+LL | Some(_) if let Some(()) = { drop(a.clone()); None } => None,
+ | ++++++++
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0382`.

src/test/ui/issues/issue-29723.rs

@@ -1,5 +1,7 @@
 // test for https://github.com/rust-lang/rust/issues/29723
 
+#![feature(if_let_guard)]
+
 fn main() {
  let s = String::new();
  let _s = match 0 {
@@ -11,4 +13,10 @@ fn main() {
  //~^ ERROR use of moved value: `s`
  }
  };
+
+ let s = String::new();
+ let _s = match 0 {
+ 0 if let Some(()) = { drop(s); None } => String::from("oops"),
+ _ => s //~ ERROR use of moved value: `s`
+ };
 }

src/test/ui/issues/issue-29723.stderr

@@ -1,5 +1,5 @@
 error[E0382]: use of moved value: `s`
- --> $DIR/issue-29723.rs:10:13
+ --> $DIR/issue-29723.rs:12:13
  |
 LL | let s = String::new();
  | - move occurs because `s` has type `String`, which does not implement the `Copy` trait
@@ -15,6 +15,22 @@ help: consider cloning the value if the performance cost is acceptable
 LL | 0 if { drop(s.clone()); false } => String::from("oops"),
  | ++++++++
 
-error: aborting due to previous error
+error[E0382]: use of moved value: `s`
+ --> $DIR/issue-29723.rs:20:14
+ |
+LL | let s = String::new();
+ | - move occurs because `s` has type `String`, which does not implement the `Copy` trait
+LL | let _s = match 0 {
+LL | 0 if let Some(()) = { drop(s); None } => String::from("oops"),
+ | - value moved here
+LL | _ => s
+ | ^ value used here after move
+ |
+help: consider cloning the value if the performance cost is acceptable
+ |
+LL | 0 if let Some(()) = { drop(s.clone()); None } => String::from("oops"),
+ | ++++++++
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0382`.

src/test/ui/nll/issue-24535-allow-mutable-borrow-in-match-guard.rs

@@ -5,6 +5,8 @@
 // See further discussion on rust-lang/rust#24535,
 // rust-lang/rfcs#1006, and rust-lang/rfcs#107
 
+#![feature(if_let_guard)]
+
 fn main() {
  rust_issue_24535();
  rfcs_issue_1006_1();
@@ -23,6 +25,12 @@ fn rust_issue_24535() {
  3 if compare(&a, &mut 3) => (),
  _ => panic!("nope"),
  }
+
+ match a {
+ 0 => panic!("nope"),
+ 3 if let true = compare(&a, &mut 3) => (),
+ _ => panic!("nope"),
+ }
 }
 
 fn rfcs_issue_1006_1() {

src/test/ui/nll/issue-27282-move-match-input-into-guard.rs

@@ -7,6 +7,8 @@
 // reaches the panic code when executed, despite the compiler warning
 // about that match arm being unreachable.
 
+#![feature(if_let_guard)]
+
 fn main() {
  let b = &mut true;
  match b {
@@ -17,4 +19,16 @@ fn main() {
  &mut true => { println!("You might think we should get here"); },
  _ => panic!("surely we could never get here, since rustc warns it is unreachable."),
  }
+
+ let b = &mut true;
+ match b {
+ //~^ ERROR use of moved value: `b` [E0382]
+ &mut false => {}
+ _ if let Some(()) = {
+ (|| { let bar = b; *bar = false; })();
+ None
+ } => {}
+ &mut true => {}
+ _ => {}
+ }
 }