Auto merge of #86995 - sexxi-goose:rewrite, r=nikomatsakis

2229: Rewrite/Refactor Closure Capture Analaysis

While handling all the differnet edge cases the code for the captur analysis got pretty compicated. Looking at the overall picture of the edge cases the rules can still be layed out simply.

Alogithm: https://hackmd.io/D3I_gwvuT-SPnJ22tgJumw

r? `@nikomatsakis`

Closes rust-lang/project-rfc-2229#52
Implementation part of rust-lang/project-rfc-2229#53

Author: bors

compiler/rustc_typeck/src/check/upvar.rs

@@ -22,8 +22,7 @@ fn big_box() {
     //~^ First Pass analysis includes:
     //~| Min Capture analysis includes:
         let p = t.0.0;
-        //~^ NOTE: Capturing t[(0, 0),Deref,(0, 0)] -> ImmBorrow
-        //~| NOTE: Capturing t[(0, 0)] -> ByValue
+        //~^ NOTE: Capturing t[(0, 0),Deref,(0, 0)] -> ByValue
         //~| NOTE: Min Capture t[(0, 0)] -> ByValue
         println!("{} {:?}", t.1, p);
         //~^ NOTE: Capturing t[(1, 0)] -> ImmBorrow

src/test/ui/closures/2229_closure_analysis/by_value.rs

@@ -19,18 +19,13 @@ LL | |
 LL | |     };
    | |_____^
    |
-note: Capturing t[(0, 0),Deref,(0, 0)] -> ImmBorrow
-  --> $DIR/by_value.rs:24:17
-   |
-LL |         let p = t.0.0;
-   |                 ^^^^^
-note: Capturing t[(0, 0)] -> ByValue
+note: Capturing t[(0, 0),Deref,(0, 0)] -> ByValue
   --> $DIR/by_value.rs:24:17
    |
 LL |         let p = t.0.0;
    |                 ^^^^^
 note: Capturing t[(1, 0)] -> ImmBorrow
-  --> $DIR/by_value.rs:28:29
+  --> $DIR/by_value.rs:27:29
    |
 LL |         println!("{} {:?}", t.1, p);
    |                             ^^^
@@ -53,7 +48,7 @@ note: Min Capture t[(0, 0)] -> ByValue
 LL |         let p = t.0.0;
    |                 ^^^^^
 note: Min Capture t[(1, 0)] -> ImmBorrow
-  --> $DIR/by_value.rs:28:29
+  --> $DIR/by_value.rs:27:29
    |
 LL |         println!("{} {:?}", t.1, p);
    |                             ^^^

src/test/ui/closures/2229_closure_analysis/by_value.stderr

@@ -16,7 +16,7 @@ fn simple_move_closure() {
     //~^ ERROR: First Pass analysis includes:
     //~| ERROR: Min Capture analysis includes:
         t.0.0 = "new S".into();
-        //~^ NOTE: Capturing t[(0, 0),(0, 0)] -> ByValue
+        //~^ NOTE: Capturing t[(0, 0),(0, 0)] -> MutBorrow
         //~| NOTE: Min Capture t[(0, 0),(0, 0)] -> ByValue
     };
     c();
@@ -78,7 +78,7 @@ fn struct_contains_ref_to_another_struct_2() {
     //~^ ERROR: First Pass analysis includes:
     //~| ERROR: Min Capture analysis includes:
         let _t = t.0.0;
-        //~^ NOTE: Capturing t[(0, 0),Deref] -> ImmBorrow
+        //~^ NOTE: Capturing t[(0, 0),Deref,(0, 0)] -> ImmBorrow
         //~| NOTE: Min Capture t[(0, 0),Deref] -> ImmBorrow
     };
 
@@ -100,8 +100,7 @@ fn struct_contains_ref_to_another_struct_3() {
     //~^ ERROR: First Pass analysis includes:
     //~| ERROR: Min Capture analysis includes:
         let _t = t.0.0;
-        //~^ NOTE: Capturing t[(0, 0),Deref] -> ImmBorrow
-        //~| NOTE: Capturing t[(0, 0)] -> ByValue
+        //~^ NOTE: Capturing t[(0, 0),Deref,(0, 0)] -> ByValue
         //~| NOTE: Min Capture t[(0, 0)] -> ByValue
     };
 
@@ -122,8 +121,7 @@ fn truncate_box_derefs() {
     //~^ ERROR: First Pass analysis includes:
     //~| ERROR: Min Capture analysis includes:
         let _t = b.0;
-        //~^ NOTE: Capturing b[Deref,(0, 0)] -> ByValue
-        //~| NOTE: Capturing b[] -> ByValue
+        //~^ NOTE: Capturing b[Deref,(0, 0)] -> ImmBorrow
         //~| NOTE: Min Capture b[] -> ByValue
     };
 
@@ -139,7 +137,7 @@ fn truncate_box_derefs() {
     //~^ ERROR: First Pass analysis includes:
     //~| ERROR: Min Capture analysis includes:
         println!("{}", b.0);
-        //~^ NOTE: Capturing b[Deref,(0, 0)] -> ByValue
+        //~^ NOTE: Capturing b[Deref,(0, 0)] -> ImmBorrow
         //~| NOTE: Min Capture b[] -> ByValue
     };
 
@@ -156,16 +154,54 @@ fn truncate_box_derefs() {
     //~^ ERROR: First Pass analysis includes:
     //~| ERROR: Min Capture analysis includes:
         println!("{}", t.1.0);
-        //~^ NOTE: Capturing t[(1, 0),Deref,(0, 0)] -> ByValue
+        //~^ NOTE: Capturing t[(1, 0),Deref,(0, 0)] -> ImmBorrow
         //~| NOTE: Min Capture t[(1, 0)] -> ByValue
     };
 }
 
+struct Foo { x: i32 }
+
+// Ensure that even in move closures, if the data is not owned by the root variable
+// then we don't truncate the derefs or a ByValue capture, rather do a reborrow
+fn box_mut_1() {
+    let mut foo = Foo { x: 0 } ;
+
+    let p_foo = &mut foo;
+    let box_p_foo = Box::new(p_foo);
+
+    let c = #[rustc_capture_analysis] move || box_p_foo.x += 10;
+    //~^ ERROR: attributes on expressions are experimental
+    //~| NOTE: see issue #15701 <https://github.com/rust-lang/rust/issues/15701>
+    //~| First Pass analysis includes:
+    //~| NOTE: Capturing box_p_foo[Deref,Deref,(0, 0)] -> UniqueImmBorrow
+    //~| Min Capture analysis includes:
+    //~| NOTE: Min Capture box_p_foo[Deref,Deref,(0, 0)] -> UniqueImmBorrow
+}
+
+// Ensure that even in move closures, if the data is not owned by the root variable
+// then we don't truncate the derefs or a ByValue capture, rather do a reborrow
+fn box_mut_2() {
+    let foo = Foo { x: 0 } ;
+
+    let mut box_foo = Box::new(foo);
+    let p_foo = &mut box_foo;
+
+    let c = #[rustc_capture_analysis] move || p_foo.x += 10;
+    //~^ ERROR: attributes on expressions are experimental
+    //~| NOTE: see issue #15701 <https://github.com/rust-lang/rust/issues/15701>
+    //~| First Pass analysis includes:
+    //~| NOTE: Capturing p_foo[Deref,Deref,(0, 0)] -> UniqueImmBorrow
+    //~| Min Capture analysis includes:
+    //~| NOTE: Min Capture p_foo[Deref,Deref,(0, 0)] -> UniqueImmBorrow
+}
+
 fn main() {
     simple_move_closure();
     simple_ref();
     struct_contains_ref_to_another_struct_1();
     struct_contains_ref_to_another_struct_2();
     struct_contains_ref_to_another_struct_3();
     truncate_box_derefs();
+    box_mut_2();
+    box_mut_1();
 }