Auto merge of #2887 - Vanille-N:tb-mut-transmute, r=RalfJung

TB: more fail tests (mostly shared with SB)

Although it was not in the tests, `mem::transmute` works for `UnsafeCell -> &` as well.

Draft: will also introduce more test cases for cases that fail.
Draft: depends on the new error messages from #2888

src/tools/miri/tests/fail/stacked_borrows/alias_through_mutation.rs → src/tools/miri/tests/fail/both_borrows/alias_through_mutation.rs

@@ -1,3 +1,6 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
+
 // This makes a ref that was passed to us via &mut alias with things it should not alias with
 fn retarget(x: &mut &u32, target: &mut u32) {
     unsafe {
@@ -11,5 +14,7 @@ fn main() {
     retarget(&mut target_alias, target);
     // now `target_alias` points to the same thing as `target`
     *target = 13;
-    let _val = *target_alias; //~ ERROR: /read access .* tag does not exist in the borrow stack/
+    let _val = *target_alias;
+    //~[stack]^ ERROR: /read access .* tag does not exist in the borrow stack/
+    //~[tree]| ERROR: /read access through .* is forbidden/
 }

src/tools/miri/tests/fail/both_borrows/alias_through_mutation.tree.stderr

@@ -0,0 +1,32 @@
+error: Undefined Behavior: read access through <TAG> is forbidden
+  --> $DIR/alias_through_mutation.rs:LL:CC
+   |
+LL |     let _val = *target_alias;
+   |                ^^^^^^^^^^^^^ read access through <TAG> is forbidden
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: the accessed tag <TAG> is a child of the conflicting tag <TAG>
+   = help: the conflicting tag <TAG> has state Disabled which forbids child read accesses
+help: the accessed tag <TAG> was created here
+  --> $DIR/alias_through_mutation.rs:LL:CC
+   |
+LL |         *x = &mut *(target as *mut _);
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^
+help: the conflicting tag <TAG> was created here, in the initial state Reserved
+  --> $DIR/alias_through_mutation.rs:LL:CC
+   |
+LL |     retarget(&mut target_alias, target);
+   |                                 ^^^^^^
+help: the conflicting tag <TAG> later transitioned to Disabled due to a foreign write access at offsets [0x0..0x4]
+  --> $DIR/alias_through_mutation.rs:LL:CC
+   |
+LL |     *target = 13;
+   |     ^^^^^^^^^^^^
+   = help: this corresponds to a loss of read and write permissions
+   = note: BACKTRACE (of the first span):
+   = note: inside `main` at $DIR/alias_through_mutation.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+

src/tools/miri/tests/fail/stacked_borrows/aliasing_mut1.rs → src/tools/miri/tests/fail/both_borrows/aliasing_mut1.rs

@@ -1,6 +1,12 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
 use std::mem;
 
-pub fn safe(_x: &mut i32, _y: &mut i32) {} //~ ERROR: protect
+pub fn safe(x: &mut i32, y: &mut i32) {
+    //~[stack]^ ERROR: protect
+    *x = 1; //~[tree] ERROR: /write access through .* is forbidden/
+    *y = 2;
+}
 
 fn main() {
     let mut x = 0;

src/tools/miri/tests/fail/stacked_borrows/aliasing_mut1.stderr → src/tools/miri/tests/fail/both_borrows/aliasing_mut1.stack.stderr

@@ -1,8 +1,8 @@
 error: Undefined Behavior: not granting access to tag <TAG> because that would remove [Unique for <TAG>] which is strongly protected because it is an argument of call ID
   --> $DIR/aliasing_mut1.rs:LL:CC
    |
-LL | pub fn safe(_x: &mut i32, _y: &mut i32) {}
-   |                           ^^ not granting access to tag <TAG> because that would remove [Unique for <TAG>] which is strongly protected because it is an argument of call ID
+LL | pub fn safe(x: &mut i32, y: &mut i32) {
+   |                          ^ not granting access to tag <TAG> because that would remove [Unique for <TAG>] which is strongly protected because it is an argument of call ID
    |
    = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
    = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
@@ -14,8 +14,8 @@ LL |     let xraw: *mut i32 = unsafe { mem::transmute(&mut x) };
 help: <TAG> is this argument
   --> $DIR/aliasing_mut1.rs:LL:CC
    |
-LL | pub fn safe(_x: &mut i32, _y: &mut i32) {}
-   |             ^^
+LL | pub fn safe(x: &mut i32, y: &mut i32) {
+   |             ^
    = note: BACKTRACE (of the first span):
    = note: inside `safe` at $DIR/aliasing_mut1.rs:LL:CC
 note: inside `main`

src/tools/miri/tests/fail/both_borrows/aliasing_mut1.tree.stderr

@@ -0,0 +1,31 @@
+error: Undefined Behavior: write access through <TAG> is forbidden
+  --> $DIR/aliasing_mut1.rs:LL:CC
+   |
+LL |     *x = 1;
+   |     ^^^^^^ write access through <TAG> is forbidden
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: the accessed tag <TAG> has state Frozen which forbids child write accesses
+help: the accessed tag <TAG> was created here, in the initial state Reserved
+  --> $DIR/aliasing_mut1.rs:LL:CC
+   |
+LL | pub fn safe(x: &mut i32, y: &mut i32) {
+   |             ^
+help: the accessed tag <TAG> later transitioned to Frozen due to a foreign read access at offsets [0x0..0x4]
+  --> $DIR/aliasing_mut1.rs:LL:CC
+   |
+LL | pub fn safe(x: &mut i32, y: &mut i32) {
+   |                          ^
+   = help: this corresponds to a loss of write permissions
+   = note: BACKTRACE (of the first span):
+   = note: inside `safe` at $DIR/aliasing_mut1.rs:LL:CC
+note: inside `main`
+  --> $DIR/aliasing_mut1.rs:LL:CC
+   |
+LL |     safe_raw(xraw, xraw);
+   |     ^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+

src/tools/miri/tests/fail/stacked_borrows/aliasing_mut2.rs → src/tools/miri/tests/fail/both_borrows/aliasing_mut2.rs

@@ -1,6 +1,12 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
 use std::mem;
 
-pub fn safe(_x: &i32, _y: &mut i32) {} //~ ERROR: protect
+pub fn safe(x: &i32, y: &mut i32) {
+    //~[stack]^ ERROR: protect
+    let _v = *x;
+    *y = 2; //~[tree] ERROR: /write access through .* is forbidden/
+}
 
 fn main() {
     let mut x = 0;

src/tools/miri/tests/fail/stacked_borrows/aliasing_mut2.stderr → src/tools/miri/tests/fail/both_borrows/aliasing_mut2.stack.stderr

@@ -1,8 +1,8 @@
 error: Undefined Behavior: not granting access to tag <TAG> because that would remove [SharedReadOnly for <TAG>] which is strongly protected because it is an argument of call ID
   --> $DIR/aliasing_mut2.rs:LL:CC
    |
-LL | pub fn safe(_x: &i32, _y: &mut i32) {}
-   |                       ^^ not granting access to tag <TAG> because that would remove [SharedReadOnly for <TAG>] which is strongly protected because it is an argument of call ID
+LL | pub fn safe(x: &i32, y: &mut i32) {
+   |                      ^ not granting access to tag <TAG> because that would remove [SharedReadOnly for <TAG>] which is strongly protected because it is an argument of call ID
    |
    = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
    = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
@@ -14,8 +14,8 @@ LL |     let xref = &mut x;
 help: <TAG> is this argument
   --> $DIR/aliasing_mut2.rs:LL:CC
    |
-LL | pub fn safe(_x: &i32, _y: &mut i32) {}
-   |             ^^
+LL | pub fn safe(x: &i32, y: &mut i32) {
+   |             ^
    = note: BACKTRACE (of the first span):
    = note: inside `safe` at $DIR/aliasing_mut2.rs:LL:CC
 note: inside `main`

src/tools/miri/tests/fail/both_borrows/aliasing_mut2.tree.stderr

@@ -0,0 +1,31 @@
+error: Undefined Behavior: write access through <TAG> is forbidden
+  --> $DIR/aliasing_mut2.rs:LL:CC
+   |
+LL |     *y = 2;
+   |     ^^^^^^ write access through <TAG> is forbidden
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: the accessed tag <TAG> has state Frozen which forbids child write accesses
+help: the accessed tag <TAG> was created here, in the initial state Reserved
+  --> $DIR/aliasing_mut2.rs:LL:CC
+   |
+LL | pub fn safe(x: &i32, y: &mut i32) {
+   |                      ^
+help: the accessed tag <TAG> later transitioned to Frozen due to a foreign read access at offsets [0x0..0x4]
+  --> $DIR/aliasing_mut2.rs:LL:CC
+   |
+LL |     let _v = *x;
+   |              ^^
+   = help: this corresponds to a loss of write permissions
+   = note: BACKTRACE (of the first span):
+   = note: inside `safe` at $DIR/aliasing_mut2.rs:LL:CC
+note: inside `main`
+  --> $DIR/aliasing_mut2.rs:LL:CC
+   |
+LL |     safe_raw(xshr, xraw);
+   |     ^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+

src/tools/miri/tests/fail/stacked_borrows/aliasing_mut3.rs → src/tools/miri/tests/fail/both_borrows/aliasing_mut3.rs

@@ -1,6 +1,12 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
 use std::mem;
 
-pub fn safe(_x: &mut i32, _y: &i32) {} //~ ERROR: borrow stack
+pub fn safe(x: &mut i32, y: &i32) {
+    //~[stack]^ ERROR: borrow stack
+    *x = 1; //~[tree] ERROR: /write access through .* is forbidden/
+    let _v = *y;
+}
 
 fn main() {
     let mut x = 0;

src/tools/miri/tests/fail/stacked_borrows/aliasing_mut3.stderr → src/tools/miri/tests/fail/both_borrows/aliasing_mut3.stack.stderr

@@ -1,11 +1,11 @@
 error: Undefined Behavior: trying to retag from <TAG> for SharedReadOnly permission at ALLOC[0x0], but that tag does not exist in the borrow stack for this location
   --> $DIR/aliasing_mut3.rs:LL:CC
    |
-LL | pub fn safe(_x: &mut i32, _y: &i32) {}
-   |                           ^^
-   |                           |
-   |                           trying to retag from <TAG> for SharedReadOnly permission at ALLOC[0x0], but that tag does not exist in the borrow stack for this location
-   |                           this error occurs as part of function-entry retag at ALLOC[0x0..0x4]
+LL | pub fn safe(x: &mut i32, y: &i32) {
+   |                          ^
+   |                          |
+   |                          trying to retag from <TAG> for SharedReadOnly permission at ALLOC[0x0], but that tag does not exist in the borrow stack for this location
+   |                          this error occurs as part of function-entry retag at ALLOC[0x0..0x4]
    |
    = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
    = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information

src/tools/miri/tests/fail/both_borrows/aliasing_mut3.tree.stderr

@@ -0,0 +1,31 @@
+error: Undefined Behavior: write access through <TAG> is forbidden
+  --> $DIR/aliasing_mut3.rs:LL:CC
+   |
+LL |     *x = 1;
+   |     ^^^^^^ write access through <TAG> is forbidden
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: the accessed tag <TAG> has state Frozen which forbids child write accesses
+help: the accessed tag <TAG> was created here, in the initial state Reserved
+  --> $DIR/aliasing_mut3.rs:LL:CC
+   |
+LL | pub fn safe(x: &mut i32, y: &i32) {
+   |             ^
+help: the accessed tag <TAG> later transitioned to Frozen due to a foreign read access at offsets [0x0..0x4]
+  --> $DIR/aliasing_mut3.rs:LL:CC
+   |
+LL | pub fn safe(x: &mut i32, y: &i32) {
+   |                          ^
+   = help: this corresponds to a loss of write permissions
+   = note: BACKTRACE (of the first span):
+   = note: inside `safe` at $DIR/aliasing_mut3.rs:LL:CC
+note: inside `main`
+  --> $DIR/aliasing_mut3.rs:LL:CC
+   |
+LL |     safe_raw(xraw, xshr);
+   |     ^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+

src/tools/miri/tests/fail/stacked_borrows/aliasing_mut4.rs → src/tools/miri/tests/fail/both_borrows/aliasing_mut4.rs

@@ -1,8 +1,15 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
+//@[tree]error-in-other-file: /write access through .* is forbidden/
 use std::cell::Cell;
 use std::mem;
 
 // Make sure &mut UnsafeCell also is exclusive
-pub fn safe(_x: &i32, _y: &mut Cell<i32>) {} //~ ERROR: protect
+pub fn safe(x: &i32, y: &mut Cell<i32>) {
+    //~[stack]^ ERROR: protect
+    y.set(1);
+    let _ = *x;
+}
 
 fn main() {
     let mut x = 0;

src/tools/miri/tests/fail/stacked_borrows/aliasing_mut4.stderr → src/tools/miri/tests/fail/both_borrows/aliasing_mut4.stack.stderr

@@ -1,8 +1,8 @@
 error: Undefined Behavior: not granting access to tag <TAG> because that would remove [SharedReadOnly for <TAG>] which is strongly protected because it is an argument of call ID
   --> $DIR/aliasing_mut4.rs:LL:CC
    |
-LL | pub fn safe(_x: &i32, _y: &mut Cell<i32>) {}
-   |                       ^^ not granting access to tag <TAG> because that would remove [SharedReadOnly for <TAG>] which is strongly protected because it is an argument of call ID
+LL | pub fn safe(x: &i32, y: &mut Cell<i32>) {
+   |                      ^ not granting access to tag <TAG> because that would remove [SharedReadOnly for <TAG>] which is strongly protected because it is an argument of call ID
    |
    = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
    = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
@@ -14,8 +14,8 @@ LL |     let xref = &mut x;
 help: <TAG> is this argument
   --> $DIR/aliasing_mut4.rs:LL:CC
    |
-LL | pub fn safe(_x: &i32, _y: &mut Cell<i32>) {}
-   |             ^^
+LL | pub fn safe(x: &i32, y: &mut Cell<i32>) {
+   |             ^
    = note: BACKTRACE (of the first span):
    = note: inside `safe` at $DIR/aliasing_mut4.rs:LL:CC
 note: inside `main`

src/tools/miri/tests/fail/both_borrows/aliasing_mut4.tree.stderr

@@ -0,0 +1,39 @@
+error: Undefined Behavior: write access through <TAG> is forbidden
+  --> RUSTLIB/core/src/mem/mod.rs:LL:CC
+   |
+LL |         ptr::write(dest, src);
+   |         ^^^^^^^^^^^^^^^^^^^^^ write access through <TAG> is forbidden
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: the accessed tag <TAG> is foreign to the protected tag <TAG> (i.e., it is not a child)
+   = help: the access would cause the protected tag <TAG> to transition from Frozen to Disabled
+   = help: this is a loss of read permissions, which is not allowed for protected tags
+help: the accessed tag <TAG> was created here
+  --> $DIR/aliasing_mut4.rs:LL:CC
+   |
+LL |     y.set(1);
+   |     ^^^^^^^^
+help: the protected tag <TAG> was created here, in the initial state Frozen
+  --> $DIR/aliasing_mut4.rs:LL:CC
+   |
+LL | pub fn safe(x: &i32, y: &mut Cell<i32>) {
+   |             ^
+   = note: BACKTRACE (of the first span):
+   = note: inside `std::mem::replace::<i32>` at RUSTLIB/core/src/mem/mod.rs:LL:CC
+   = note: inside `std::cell::Cell::<i32>::replace` at RUSTLIB/core/src/cell.rs:LL:CC
+   = note: inside `std::cell::Cell::<i32>::set` at RUSTLIB/core/src/cell.rs:LL:CC
+note: inside `safe`
+  --> $DIR/aliasing_mut4.rs:LL:CC
+   |
+LL |     y.set(1);
+   |     ^^^^^^^^
+note: inside `main`
+  --> $DIR/aliasing_mut4.rs:LL:CC
+   |
+LL |     safe_raw(xshr, xraw as *mut _);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+

src/tools/miri/tests/fail/stacked_borrows/box_noalias_violation.rs → src/tools/miri/tests/fail/both_borrows/box_noalias_violation.rs

@@ -1,8 +1,13 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
+
 unsafe fn test(mut x: Box<i32>, y: *const i32) -> i32 {
     // We will call this in a way that x and y alias.
     *x = 5;
     std::mem::forget(x);
-    *y //~ERROR: weakly protected
+    *y
+    //~[stack]^ ERROR: weakly protected
+    //~[tree]| ERROR: /read access through .* is forbidden/
 }
 
 fn main() {

src/tools/miri/tests/fail/both_borrows/box_noalias_violation.tree.stderr

@@ -0,0 +1,38 @@
+error: Undefined Behavior: read access through <TAG> is forbidden
+  --> $DIR/box_noalias_violation.rs:LL:CC
+   |
+LL |     *y
+   |     ^^ read access through <TAG> is forbidden
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: the accessed tag <TAG> is foreign to the protected tag <TAG> (i.e., it is not a child)
+   = help: the access would cause the protected tag <TAG> to transition from Active to Frozen
+   = help: this is a loss of write permissions, which is not allowed for protected tags
+help: the accessed tag <TAG> was created here
+  --> $DIR/box_noalias_violation.rs:LL:CC
+   |
+LL |         let ptr = &mut v as *mut i32;
+   |                   ^^^^^^
+help: the protected tag <TAG> was created here, in the initial state Reserved
+  --> $DIR/box_noalias_violation.rs:LL:CC
+   |
+LL | unsafe fn test(mut x: Box<i32>, y: *const i32) -> i32 {
+   |                ^^^^^
+help: the protected tag <TAG> later transitioned to Active due to a child write access at offsets [0x0..0x4]
+  --> $DIR/box_noalias_violation.rs:LL:CC
+   |
+LL |     *x = 5;
+   |     ^^^^^^
+   = help: this corresponds to the first write to a 2-phase borrowed mutable reference
+   = note: BACKTRACE (of the first span):
+   = note: inside `test` at $DIR/box_noalias_violation.rs:LL:CC
+note: inside `main`
+  --> $DIR/box_noalias_violation.rs:LL:CC
+   |
+LL |         test(Box::from_raw(ptr), ptr);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+

src/tools/miri/tests/fail/stacked_borrows/buggy_as_mut_slice.rs → src/tools/miri/tests/fail/both_borrows/buggy_as_mut_slice.rs

@@ -1,3 +1,5 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
 mod safe {
     use std::slice::from_raw_parts_mut;
 
@@ -9,7 +11,9 @@ mod safe {
 fn main() {
     let v = vec![0, 1, 2];
     let v1 = safe::as_mut_slice(&v);
-    let _v2 = safe::as_mut_slice(&v);
+    let v2 = safe::as_mut_slice(&v);
     v1[1] = 5;
-    //~^ ERROR: /write access .* tag does not exist in the borrow stack/
+    //~[stack]^ ERROR: /write access .* tag does not exist in the borrow stack/
+    v2[1] = 7;
+    //~[tree]^ ERROR: /write access through .* is forbidden/
 }