Add assertion details to panic info.

de-vri-es · jakoschiko · commit 0df6e3394985 · 2021-10-20T21:22:18.000+02:00
The assertion details are added as a new enum field, allowing for future
extensions with different information for other sources of panics.
For example, `.unwrap()` could extend the enum to store a `&amp;dyn Error`
in the panic info.

The panic handler in `std` passes the additional info unmodified to the
panic hook.
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
@@ -41,7 +41,14 @@ macro_rules! assert_eq {
                     // The reborrows below are intentional. Without them, the stack slot for the
                     // borrow is initialized even before the values are compared, leading to a
                     // noticeable slow down.
-                    $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::None);
+                    $crate::panicking::assert_failed(
+                        kind,
+                        $crate::stringify!($left),
+                        &*left_val,
+                        $crate::stringify!($right),
+                        &*right_val,
+                        $crate::option::Option::None,
+                    );
                 }
             }
         }
@@ -54,7 +61,14 @@ macro_rules! assert_eq {
                     // The reborrows below are intentional. Without them, the stack slot for the
                     // borrow is initialized even before the values are compared, leading to a
                     // noticeable slow down.
-                    $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::Some($crate::format_args!($($arg)+)));
+                    $crate::panicking::assert_failed(
+                        kind,
+                        $crate::stringify!($left),
+                        &*left_val,
+                        $crate::stringify!($right),
+                        &*right_val,
+                        $crate::option::Option::Some($crate::format_args!($($arg)+)),
+                    );
                 }
             }
         }
@@ -90,7 +104,14 @@ macro_rules! assert_ne {
                     // The reborrows below are intentional. Without them, the stack slot for the
                     // borrow is initialized even before the values are compared, leading to a
                     // noticeable slow down.
-                    $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::None);
+                    $crate::panicking::assert_failed(
+                        kind,
+                        $crate::stringify!($left),
+                        &*left_val,
+                        $crate::stringify!($right),
+                        &*right_val,
+                        $crate::option::Option::None,
+                    );
                 }
             }
         }
@@ -103,7 +124,14 @@ macro_rules! assert_ne {
                     // The reborrows below are intentional. Without them, the stack slot for the
                     // borrow is initialized even before the values are compared, leading to a
                     // noticeable slow down.
-                    $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::Some($crate::format_args!($($arg)+)));
+                    $crate::panicking::assert_failed(
+                        kind,
+                        $crate::stringify!($left),
+                        &*left_val,
+                        $crate::stringify!($right),
+                        &*right_val,
+                        $crate::option::Option::Some($crate::format_args!($($arg)+)),
+                    );
                 }
             }
         }
@@ -145,6 +173,7 @@ pub macro assert_matches {
             $( $pattern )|+ $( if $guard )? => {}
             ref left_val => {
                 $crate::panicking::assert_matches_failed(
+                    $crate::stringify!($left),
                     left_val,
                     $crate::stringify!($($pattern)|+ $(if $guard)?),
                     $crate::option::Option::None
@@ -157,6 +186,7 @@ pub macro assert_matches {
             $( $pattern )|+ $( if $guard )? => {}
             ref left_val => {
                 $crate::panicking::assert_matches_failed(
+                    $crate::stringify!($left),
                     left_val,
                     $crate::stringify!($($pattern)|+ $(if $guard)?),
                     $crate::option::Option::Some($crate::format_args!($($arg)+))
diff --git a/library/core/src/panic.rs b/library/core/src/panic.rs
@@ -5,6 +5,20 @@
 mod location;
 mod panic_info;
 mod unwind_safe;
+#[unstable(
+    feature = "panic_internals",
+    reason = "internal details of the implementation of the `panic!` and related macros",
+    issue = "none"
+)]
+#[doc(hidden)]
+pub mod assert_info;
+#[unstable(
+    feature = "panic_internals",
+    reason = "internal details of the implementation of the `panic!` and related macros",
+    issue = "none"
+)]
+#[doc(hidden)]
+pub mod extra_info;
 
 use crate::any::Any;
 
@@ -36,7 +50,10 @@ pub macro panic_2015 {
         $crate::panicking::panic_display(&$arg)
     ),
     ($fmt:expr, $($arg:tt)+) => (
-        $crate::panicking::panic_fmt($crate::const_format_args!($fmt, $($arg)+))
+        $crate::panicking::panic_fmt(
+            $crate::const_format_args!($fmt, $($arg)+),
+            $crate::option::Option::None,
+        )
     ),
 }
 
@@ -54,7 +71,10 @@ pub macro panic_2021 {
         $crate::panicking::panic_display(&$arg)
     ),
     ($($t:tt)+) => (
-        $crate::panicking::panic_fmt($crate::const_format_args!($($t)+))
+        $crate::panicking::panic_fmt(
+            $crate::const_format_args!($($t)+),
+            $crate::option::Option::None,
+        )
     ),
 }
 
diff --git a/library/core/src/panic/assert_info.rs b/library/core/src/panic/assert_info.rs
@@ -0,0 +1,52 @@
+use crate::fmt::Debug;
+
+/// Information about a failed assertion.
+#[derive(Debug)]
+pub struct AssertInfo<'a> {
+    /// The assertion that failed.
+    pub assertion: Assertion<'a>,
+    /// Optional additional message to include in the failure report.
+    pub message: Option<crate::fmt::Arguments<'a>>,
+}
+
+#[derive(Debug)]
+pub enum Assertion<'a> {
+    /// The assertion is a boolean assertion.
+    Bool(BoolAssertion),
+    /// The assertion is a binary comparison assertion.
+    Binary(BinaryAssertion<'a>),
+}
+
+/// Information about a failed boolean assertion.
+#[derive(Debug)]
+pub struct BoolAssertion {
+    /// The expression that was evaluated.
+    pub expr: &'static str,
+}
+
+/// Information about a failed binary comparison assertion.
+#[derive(Debug)]
+pub struct BinaryAssertion<'a> {
+    /// The operator used to compare left and right.
+    pub op: &'static str,
+    /// The left expression as string.
+    pub left_expr: &'static str,
+    /// The right expression as string.
+    pub right_expr: &'static str,
+    /// The value of the left expression.
+    pub left_val: &'a dyn Debug,
+    /// The value of the right expression.
+    pub right_val: &'a dyn Debug,
+}
+
+impl<'a> From<BoolAssertion> for Assertion<'a> {
+    fn from(other: BoolAssertion) -> Self {
+        Self::Bool(other)
+    }
+}
+
+impl<'a> From<BinaryAssertion<'a>> for Assertion<'a> {
+    fn from(other: BinaryAssertion<'a>) -> Self {
+        Self::Binary(other)
+    }
+}
diff --git a/library/core/src/panic/extra_info.rs b/library/core/src/panic/extra_info.rs
@@ -0,0 +1,6 @@
+use crate::panic::assert_info::AssertInfo;
+
+#[derive(Debug, Copy, Clone)]
+pub enum ExtraInfo<'a> {
+    AssertInfo(&'a AssertInfo<'a>),
+}
diff --git a/library/core/src/panic/panic_info.rs b/library/core/src/panic/panic_info.rs
@@ -1,5 +1,7 @@
 use crate::any::Any;
 use crate::fmt;
+use crate::panic::assert_info::AssertInfo;
+use crate::panic::extra_info::ExtraInfo;
 use crate::panic::Location;
 
 /// A struct providing information about a panic.
@@ -31,6 +33,7 @@ pub struct PanicInfo<'a> {
     payload: &'a (dyn Any + Send),
     message: Option<&'a fmt::Arguments<'a>>,
     location: &'a Location<'a>,
+    extra_info: Option<ExtraInfo<'a>>,
 }
 
 impl<'a> PanicInfo<'a> {
@@ -46,7 +49,7 @@ impl<'a> PanicInfo<'a> {
         location: &'a Location<'a>,
     ) -> Self {
         struct NoPayload;
-        PanicInfo { location, message, payload: &NoPayload }
+        PanicInfo { location, message, payload: &NoPayload, extra_info: None }
     }
 
     #[unstable(
@@ -124,6 +127,40 @@ impl<'a> PanicInfo<'a> {
         // deal with that case in std::panicking::default_hook and core::panicking::panic_fmt.
         Some(&self.location)
     }
+
+    #[unstable(
+        feature = "panic_internals",
+        reason = "internal details of the implementation of the `panic!` and related macros",
+        issue = "none"
+    )]
+    #[doc(hidden)]
+    #[inline]
+    pub fn set_extra_info(&mut self, info: Option<ExtraInfo<'a>>) {
+        self.extra_info = info;
+    }
+
+    #[unstable(
+        feature = "panic_internals",
+        reason = "internal details of the implementation of the `panic!` and related macros",
+        issue = "none"
+    )]
+    #[doc(hidden)]
+    #[inline]
+    pub fn extra_info(&self) -> Option<ExtraInfo<'_>> {
+        self.extra_info
+    }
+
+    /// Get the information about the assertion that caused the panic.
+    ///
+    /// Returns `None` if the panic was not caused by an assertion.
+    #[unstable(
+        feature = "panic_internals",
+        reason = "internal details of the implementation of the `panic!` and related macros",
+        issue = "none"
+    )]
+    pub fn assert_info(&self) -> Option<&AssertInfo<'_>> {
+        if let Some(ExtraInfo::AssertInfo(x)) = &self.extra_info { Some(x) } else { None }
+    }
 }
 
 #[stable(feature = "panic_hook_display", since = "1.26.0")]
diff --git a/library/core/src/panicking.rs b/library/core/src/panicking.rs
diff --git a/library/std/src/panicking.rs b/library/std/src/panicking.rs
