Auto merge of #67524 - LukasKalbertodt:improve-into-iter-lint, r=matthewjasper

bors · bors · commit ed33453a37d6 · 2019-12-25T10:20:48.000Z
Generalize `array_into_iter` lint to also lint for boxed arrays `Box` is special in that a method call on a box can move the value out of the box. Thus, the same backwards-compatibility problem can arise for boxed arrays as for simple arrays. --- CC #66145 r? @matthewjasper (as you reviewed the first PR)
diff --git a/src/librustc_lint/array_into_iter.rs b/src/librustc_lint/array_into_iter.rs
@@ -44,14 +44,26 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ArrayIntoIter {
             // argument.
             let receiver_arg = &args[0];
 
-            // Test if the original `self` type is an array type.
-            match cx.tables.expr_ty(receiver_arg).kind {
-                ty::Array(..) => {}
-                _ => return,
+            // Peel all `Box<_>` layers. We have to special case `Box` here as
+            // `Box` is the only thing that values can be moved out of via
+            // method call. `Box::new([1]).into_iter()` should trigger this
+            // lint.
+            let mut recv_ty = cx.tables.expr_ty(receiver_arg);
+            let mut num_box_derefs = 0;
+            while recv_ty.is_box() {
+                num_box_derefs += 1;
+                recv_ty = recv_ty.boxed_ty();
+            }
+
+            // Make sure we found an array after peeling the boxes.
+            if !matches!(recv_ty.kind, ty::Array(..)) {
+                return;
             }
 
-            // Make sure that the first adjustment is an autoref coercion.
-            match cx.tables.expr_adjustments(receiver_arg).get(0) {
+            // Make sure that there is an autoref coercion at the expected
+            // position. The first `num_box_derefs` adjustments are the derefs
+            // of the box.
+            match cx.tables.expr_adjustments(receiver_arg).get(num_box_derefs) {
                 Some(Adjustment { kind: Adjust::Borrow(_), .. }) => {}
                 _ => return,
             }
diff --git a/src/test/ui/iterators/into-iter-on-arrays-lint.fixed b/src/test/ui/iterators/into-iter-on-arrays-lint.fixed
@@ -19,6 +19,31 @@ fn main() {
     //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
     //~| WARNING this was previously accepted by the compiler but is being phased out
 
+    Box::new(small).iter();
+    //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new([1, 2]).iter();
+    //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new(big).iter();
+    //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new([0u8; 33]).iter();
+    //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+
+    Box::new(Box::new(small)).iter();
+    //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new(Box::new([1, 2])).iter();
+    //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new(Box::new(big)).iter();
+    //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new(Box::new([0u8; 33])).iter();
+    //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
 
     // Expressions that should not
     (&[1, 2]).into_iter();
diff --git a/src/test/ui/iterators/into-iter-on-arrays-lint.rs b/src/test/ui/iterators/into-iter-on-arrays-lint.rs
@@ -19,6 +19,31 @@ fn main() {
     //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
     //~| WARNING this was previously accepted by the compiler but is being phased out
 
+    Box::new(small).into_iter();
+    //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new([1, 2]).into_iter();
+    //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new(big).into_iter();
+    //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new([0u8; 33]).into_iter();
+    //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+
+    Box::new(Box::new(small)).into_iter();
+    //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new(Box::new([1, 2])).into_iter();
+    //~^ WARNING this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new(Box::new(big)).into_iter();
+    //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
+    Box::new(Box::new([0u8; 33])).into_iter();
+    //~^ WARNING this method call currently resolves to `<&[T] as IntoIterator>::into_iter`
+    //~| WARNING this was previously accepted by the compiler but is being phased out
 
     // Expressions that should not
     (&[1, 2]).into_iter();
diff --git a/src/test/ui/iterators/into-iter-on-arrays-lint.stderr b/src/test/ui/iterators/into-iter-on-arrays-lint.stderr
@@ -35,3 +35,75 @@ LL |     [0u8; 33].into_iter();
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
 
+warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
+  --> $DIR/into-iter-on-arrays-lint.rs:22:21
+   |
+LL |     Box::new(small).into_iter();
+   |                     ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+
+warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
+  --> $DIR/into-iter-on-arrays-lint.rs:25:22
+   |
+LL |     Box::new([1, 2]).into_iter();
+   |                      ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+
+warning: this method call currently resolves to `<&[T] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
+  --> $DIR/into-iter-on-arrays-lint.rs:28:19
+   |
+LL |     Box::new(big).into_iter();
+   |                   ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+
+warning: this method call currently resolves to `<&[T] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
+  --> $DIR/into-iter-on-arrays-lint.rs:31:25
+   |
+LL |     Box::new([0u8; 33]).into_iter();
+   |                         ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+
+warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
+  --> $DIR/into-iter-on-arrays-lint.rs:35:31
+   |
+LL |     Box::new(Box::new(small)).into_iter();
+   |                               ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+
+warning: this method call currently resolves to `<&[T; N] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
+  --> $DIR/into-iter-on-arrays-lint.rs:38:32
+   |
+LL |     Box::new(Box::new([1, 2])).into_iter();
+   |                                ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+
+warning: this method call currently resolves to `<&[T] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
+  --> $DIR/into-iter-on-arrays-lint.rs:41:29
+   |
+LL |     Box::new(Box::new(big)).into_iter();
+   |                             ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+
+warning: this method call currently resolves to `<&[T] as IntoIterator>::into_iter` (due to autoref coercions), but that might change in the future when `IntoIterator` impls for arrays are added.
+  --> $DIR/into-iter-on-arrays-lint.rs:44:35
+   |
+LL |     Box::new(Box::new([0u8; 33])).into_iter();
+   |                                   ^^^^^^^^^ help: use `.iter()` instead of `.into_iter()` to avoid ambiguity: `iter`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+
