From fe08d9e2d270d97be5a33a2d505d4a9ea56d258a Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sat, 3 Aug 2019 20:35:52 +0200
Subject: [PATCH 1/4] also add macros for free-form error messages

---
 src/librustc/mir/interpret/mod.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/librustc/mir/interpret/mod.rs b/src/librustc/mir/interpret/mod.rs
index 65f4c9c47d0a9..1ec95c29a4a6f 100644
--- a/src/librustc/mir/interpret/mod.rs
+++ b/src/librustc/mir/interpret/mod.rs
@@ -9,6 +9,11 @@ macro_rules! err_unsup {
     };
 }
 
+#[macro_export]
+macro_rules! err_unsup_format {
+    ($($tt:tt)*) => { err_unsup!(Unsupported(format!($($tt)*))) };
+}
+
 #[macro_export]
 macro_rules! err_inval {
     ($($tt:tt)*) => {
@@ -27,6 +32,11 @@ macro_rules! err_ub {
     };
 }
 
+#[macro_export]
+macro_rules! err_ub_format {
+    ($($tt:tt)*) => { err_ub!(Ub(format!($($tt)*))) };
+}
+
 #[macro_export]
 macro_rules! err_panic {
     ($($tt:tt)*) => {

From 89a370db0f6caef02b34cd42a151ef21613a8b44 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sat, 3 Aug 2019 20:36:05 +0200
Subject: [PATCH 2/4] add variant for experimental UB (like Stacked Borrows)

---
 src/librustc/mir/interpret/error.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/librustc/mir/interpret/error.rs b/src/librustc/mir/interpret/error.rs
index 6a8cd9b46ae4a..5d60108f37c1d 100644
--- a/src/librustc/mir/interpret/error.rs
+++ b/src/librustc/mir/interpret/error.rs
@@ -342,8 +342,10 @@ impl fmt::Debug for InvalidProgramInfo<'tcx> {
 
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub enum UndefinedBehaviorInfo {
-    /// Handle cases which for which we do not have a fixed variant.
+    /// Free-form case. Only for errors that are never caught!
     Ub(String),
+    /// Free-form case for experimental UB. Only for errors that are never caught!
+    UbExperimental(String),
     /// Unreachable code was executed.
     Unreachable,
 }
@@ -352,7 +354,7 @@ impl fmt::Debug for UndefinedBehaviorInfo {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use UndefinedBehaviorInfo::*;
         match self {
-            Ub(ref msg) =>
+            Ub(msg) | UbExperimental(msg) =>
                 write!(f, "{}", msg),
             Unreachable =>
                 write!(f, "entered unreachable code"),
@@ -362,7 +364,7 @@ impl fmt::Debug for UndefinedBehaviorInfo {
 
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub enum UnsupportedOpInfo<'tcx> {
-    /// Handle cases which for which we do not have a fixed variant.
+    /// Free-form case. Only for errors that are never caught!
     Unsupported(String),
 
     // -- Everything below is not classified yet --

From 18daa766f058217e0b2f53d34e02c8a64b341141 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 4 Aug 2019 11:21:41 +0200
Subject: [PATCH 3/4] move AssumptionNotHeld to UB

---
 src/librustc/mir/interpret/error.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/librustc/mir/interpret/error.rs b/src/librustc/mir/interpret/error.rs
index 5d60108f37c1d..f1baebd34a40c 100644
--- a/src/librustc/mir/interpret/error.rs
+++ b/src/librustc/mir/interpret/error.rs
@@ -348,6 +348,8 @@ pub enum UndefinedBehaviorInfo {
     UbExperimental(String),
     /// Unreachable code was executed.
     Unreachable,
+    /// An `assume` was run on a `false` condition,
+    AssumptionNotHeld,
 }
 
 impl fmt::Debug for UndefinedBehaviorInfo {
@@ -358,6 +360,8 @@ impl fmt::Debug for UndefinedBehaviorInfo {
                 write!(f, "{}", msg),
             Unreachable =>
                 write!(f, "entered unreachable code"),
+            AssumptionNotHeld =>
+                write!(f, "`assume` argument was false"),
         }
     }
 }
@@ -408,7 +412,6 @@ pub enum UnsupportedOpInfo<'tcx> {
     VtableForArgumentlessMethod,
     ModifiedConstantMemory,
     ModifiedStatic,
-    AssumptionNotHeld,
     TypeNotPrimitive(Ty<'tcx>),
     ReallocatedWrongMemoryKind(String, String),
     DeallocatedWrongMemoryKind(String, String),
@@ -507,8 +510,6 @@ impl fmt::Debug for UnsupportedOpInfo<'tcx> {
             ModifiedStatic =>
                 write!(f, "tried to modify a static's initial value from another static's \
                     initializer"),
-            AssumptionNotHeld =>
-                write!(f, "`assume` argument was false"),
             ReallocateNonBasePtr =>
                 write!(f, "tried to reallocate with a pointer not to the beginning of an \
                     existing object"),

From b9d4c759f3022c2f7c4334ef7b727044aee03915 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 4 Aug 2019 11:59:14 +0200
Subject: [PATCH 4/4] AssumptionNotHeld is used only once in Miri and never
 caught... remove from enum

---
 src/librustc/mir/interpret/error.rs | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/src/librustc/mir/interpret/error.rs b/src/librustc/mir/interpret/error.rs
index f1baebd34a40c..aa36b55ae376e 100644
--- a/src/librustc/mir/interpret/error.rs
+++ b/src/librustc/mir/interpret/error.rs
@@ -348,8 +348,6 @@ pub enum UndefinedBehaviorInfo {
     UbExperimental(String),
     /// Unreachable code was executed.
     Unreachable,
-    /// An `assume` was run on a `false` condition,
-    AssumptionNotHeld,
 }
 
 impl fmt::Debug for UndefinedBehaviorInfo {
@@ -360,8 +358,6 @@ impl fmt::Debug for UndefinedBehaviorInfo {
                 write!(f, "{}", msg),
             Unreachable =>
                 write!(f, "entered unreachable code"),
-            AssumptionNotHeld =>
-                write!(f, "`assume` argument was false"),
         }
     }
 }