Switch to custom Not trait instead of '!' operator

src/ensure.rs

@@ -815,24 +815,24 @@ macro_rules! __fancy_ensure {
 #[macro_export]
 macro_rules! __fallback_ensure {
     ($cond:expr $(,)?) => {
-        if !$cond {
+        if $crate::__private::not($cond) {
             return $crate::__private::Err($crate::Error::msg(
                 $crate::__private::concat!("Condition failed: `", $crate::__private::stringify!($cond), "`")
             ));
         }
     };
     ($cond:expr, $msg:literal $(,)?) => {
-        if !$cond {
+        if $crate::__private::not($cond) {
             return $crate::__private::Err($crate::__anyhow!($msg));
         }
     };
     ($cond:expr, $err:expr $(,)?) => {
-        if !$cond {
+        if $crate::__private::not($cond) {
             return $crate::__private::Err($crate::__anyhow!($err));
         }
     };
     ($cond:expr, $fmt:expr, $($arg:tt)*) => {
-        if !$cond {
+        if $crate::__private::not($cond) {
             return $crate::__private::Err($crate::__anyhow!($fmt, $($arg)*));
         }
     };

src/lib.rs

@@ -651,6 +651,7 @@ pub fn Ok<T>(t: T) -> Result<T> {
 // Not public API. Referenced by macro-generated code.
 #[doc(hidden)]
 pub mod __private {
+    use self::not::Bool;
     use crate::Error;
     use alloc::fmt;
     use core::fmt::Arguments;
@@ -699,4 +700,31 @@ pub mod __private {
     pub fn must_use(error: Error) -> Error {
         error
     }
+
+    #[doc(hidden)]
+    #[inline]
+    pub fn not(cond: impl Bool) -> bool {
+        cond.not()
+    }
+
+    mod not {
+        #[doc(hidden)]
+        pub trait Bool {
+            fn not(self) -> bool;
+        }
+
+        impl Bool for bool {
+            #[inline]
+            fn not(self) -> bool {
+                !self
+            }
+        }
+
+        impl Bool for &bool {
+            #[inline]
+            fn not(self) -> bool {
+                !*self
+            }
+        }
+    }
 }

tests/test_macros.rs

@@ -15,7 +15,6 @@ use self::common::*;
 use anyhow::{anyhow, ensure, Result};
 use std::cell::Cell;
 use std::future;
-use std::ops::Not;
 
 #[test]
 fn test_messages() {
@@ -61,20 +60,11 @@ fn test_ensure_nonbool() -> Result<()> {
         condition: bool,
     }
 
-    impl Not for Struct {
-        type Output = bool;
-        fn not(self) -> Self::Output {
-            !self.condition
-        }
-    }
-
     let s = Struct { condition: true };
     match &s {
         Struct { condition } => ensure!(condition), // &bool
     }
 
-    ensure!(s);
-
     Ok(())
 }
 

tests/ui/ensure-nonbool.rs

@@ -1,17 +1,26 @@
 use anyhow::{ensure, Result};
-use std::ops::Deref;
+use std::ops::{Deref, Not};
 
 struct Bool(bool);
 
 struct DerefBool(bool);
 
+struct NotBool(bool);
+
 impl Deref for DerefBool {
     type Target = bool;
     fn deref(&self) -> &Self::Target {
         &self.0
     }
 }
 
+impl Not for NotBool {
+    type Output = bool;
+    fn not(self) -> Self::Output {
+        !self.0
+    }
+}
+
 fn main() -> Result<()> {
     ensure!("...");
 
@@ -24,5 +33,8 @@ fn main() -> Result<()> {
     ensure!(db);
     ensure!(&db);
 
+    let nb = NotBool(true);
+    ensure!(nb);
+
     Ok(())
 }

tests/ui/ensure-nonbool.stderr

@@ -1,41 +1,91 @@
-error[E0600]: cannot apply unary operator `!` to type `&'static str`
-  --> tests/ui/ensure-nonbool.rs:16:5
+error[E0277]: the trait bound `&str: __private::not::Bool` is not satisfied
+  --> tests/ui/ensure-nonbool.rs:25:13
    |
-16 |     ensure!("...");
-   |     ^^^^^^^^^^^^^^ cannot apply unary operator `!`
+25 |     ensure!("...");
+   |     --------^^^^^-
+   |     |       |
+   |     |       the trait `__private::not::Bool` is not implemented for `&str`
+   |     required by a bound introduced by this call
    |
-   = note: this error originates in the macro `$crate::__fallback_ensure` which comes from the expansion of the macro `ensure` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = help: the following other types implement trait `__private::not::Bool`:
+             &bool
+             bool
+note: required by a bound in `anyhow::__private::not`
+  --> src/lib.rs
+   |
+   |     pub fn not(cond: impl Bool) -> bool {
+   |                           ^^^^ required by this bound in `not`
 
-error[E0600]: cannot apply unary operator `!` to type `&mut bool`
-  --> tests/ui/ensure-nonbool.rs:20:23
+error[E0277]: the trait bound `&mut bool: __private::not::Bool` is not satisfied
+  --> tests/ui/ensure-nonbool.rs:29:31
+   |
+29 |         Bool(cond) => ensure!(cond),
+   |                       --------^^^^-
+   |                       |       |
+   |                       |       the trait `__private::not::Bool` is not implemented for `&mut bool`
+   |                       required by a bound introduced by this call
    |
-20 |         Bool(cond) => ensure!(cond),
-   |                       ^^^^^^^^^^^^^ cannot apply unary operator `!`
+   = help: the following other types implement trait `__private::not::Bool`:
+             &bool
+             bool
+   = note: `__private::not::Bool` is implemented for `&bool`, but not for `&mut bool`
+note: required by a bound in `anyhow::__private::not`
+  --> src/lib.rs
    |
-   = note: this error originates in the macro `$crate::__fallback_ensure` which comes from the expansion of the macro `ensure` (in Nightly builds, run with -Z macro-backtrace for more info)
+   |     pub fn not(cond: impl Bool) -> bool {
+   |                           ^^^^ required by this bound in `not`
 
-error[E0600]: cannot apply unary operator `!` to type `DerefBool`
-  --> tests/ui/ensure-nonbool.rs:24:5
+error[E0277]: the trait bound `DerefBool: __private::not::Bool` is not satisfied
+  --> tests/ui/ensure-nonbool.rs:33:13
    |
-24 |     ensure!(db);
-   |     ^^^^^^^^^^^ cannot apply unary operator `!`
+33 |     ensure!(db);
+   |     --------^^-
+   |     |       |
+   |     |       the trait `__private::not::Bool` is not implemented for `DerefBool`
+   |     required by a bound introduced by this call
    |
-note: an implementation of `Not` might be missing for `DerefBool`
-  --> tests/ui/ensure-nonbool.rs:6:1
+   = help: the following other types implement trait `__private::not::Bool`:
+             &bool
+             bool
+note: required by a bound in `anyhow::__private::not`
+  --> src/lib.rs
+   |
+   |     pub fn not(cond: impl Bool) -> bool {
+   |                           ^^^^ required by this bound in `not`
+
+error[E0277]: the trait bound `&DerefBool: __private::not::Bool` is not satisfied
+  --> tests/ui/ensure-nonbool.rs:34:13
    |
-6  | struct DerefBool(bool);
-   | ^^^^^^^^^^^^^^^^ must implement `Not`
-note: the trait `Not` must be implemented
-  --> $RUST/core/src/ops/bit.rs
+34 |     ensure!(&db);
+   |     --------^^^-
+   |     |       |
+   |     |       the trait `__private::not::Bool` is not implemented for `&DerefBool`
+   |     required by a bound introduced by this call
    |
-   | pub trait Not {
-   | ^^^^^^^^^^^^^
-   = note: this error originates in the macro `$crate::__fallback_ensure` which comes from the expansion of the macro `ensure` (in Nightly builds, run with -Z macro-backtrace for more info)
+note: required by a bound in `anyhow::__private::not`
+  --> src/lib.rs
+   |
+   |     pub fn not(cond: impl Bool) -> bool {
+   |                           ^^^^ required by this bound in `not`
+help: consider dereferencing here
+   |
+34 |     ensure!(&*db);
+   |              +
 
-error[E0600]: cannot apply unary operator `!` to type `&DerefBool`
-  --> tests/ui/ensure-nonbool.rs:25:5
+error[E0277]: the trait bound `NotBool: __private::not::Bool` is not satisfied
+  --> tests/ui/ensure-nonbool.rs:37:13
+   |
+37 |     ensure!(nb);
+   |     --------^^-
+   |     |       |
+   |     |       the trait `__private::not::Bool` is not implemented for `NotBool`
+   |     required by a bound introduced by this call
    |
-25 |     ensure!(&db);
-   |     ^^^^^^^^^^^^ cannot apply unary operator `!`
+   = help: the following other types implement trait `__private::not::Bool`:
+             &bool
+             bool
+note: required by a bound in `anyhow::__private::not`
+  --> src/lib.rs
    |
-   = note: this error originates in the macro `$crate::__fallback_ensure` which comes from the expansion of the macro `ensure` (in Nightly builds, run with -Z macro-backtrace for more info)
+   |     pub fn not(cond: impl Bool) -> bool {
+   |                           ^^^^ required by this bound in `not`