From 9ee4d1aadc7f4151193a7f53d1fcbb4fddf40ece Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Wed, 15 Apr 2020 12:18:20 +0200
Subject: [PATCH] reword Miri validity errors: undefined -> uninitialized

---
 src/librustc_mir/interpret/validity.rs          | 17 +++++++++++------
 .../ui/consts/const-eval/ub-wide-ptr.stderr     |  4 ++--
 src/test/ui/consts/const-eval/union-ice.stderr  |  2 +-
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/src/librustc_mir/interpret/validity.rs b/src/librustc_mir/interpret/validity.rs
index 701e394415b..d60f6f38d07 100644
--- a/src/librustc_mir/interpret/validity.rs
+++ b/src/librustc_mir/interpret/validity.rs
@@ -322,7 +322,11 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
         let value = self.ecx.read_immediate(value)?;
         // Handle wide pointers.
         // Check metadata early, for better diagnostics
-        let place = try_validation!(self.ecx.ref_to_mplace(value), "undefined pointer", self.path);
+        let place = try_validation!(
+            self.ecx.ref_to_mplace(value),
+            format_args!("uninitialized {}", kind),
+            self.path
+        );
         if place.layout.is_unsized() {
             self.check_wide_ptr_meta(place.meta, place.layout)?;
         }
@@ -334,7 +338,7 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
                     format_args!("invalid {} metadata: {}", kind, msg),
                     self.path
                 ),
-                _ => bug!("Unexpected error during ptr size_and_align_of: {}", err),
+                _ => bug!("unexpected error during ptr size_and_align_of: {}", err),
             },
         };
         let (size, align) = size_and_align
@@ -477,10 +481,11 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
             }
             ty::RawPtr(..) => {
                 // We are conservative with undef for integers, but try to
-                // actually enforce our current rules for raw pointers.
+                // actually enforce the strict rules for raw pointers (mostly because
+                // that lets us re-use `ref_to_mplace`).
                 let place = try_validation!(
                     self.ecx.ref_to_mplace(self.ecx.read_immediate(value)?),
-                    "undefined pointer",
+                    "uninitialized raw pointer",
                     self.path
                 );
                 if place.layout.is_unsized() {
@@ -776,14 +781,14 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                         // For some errors we might be able to provide extra information
                         match err.kind {
                             err_ub!(InvalidUndefBytes(Some(ptr))) => {
-                                // Some byte was undefined, determine which
+                                // Some byte was uninitialized, determine which
                                 // element that byte belongs to so we can
                                 // provide an index.
                                 let i = usize::try_from(ptr.offset.bytes() / layout.size.bytes())
                                     .unwrap();
                                 self.path.push(PathElem::ArrayElem(i));
 
-                                throw_validation_failure!("undefined bytes", self.path)
+                                throw_validation_failure!("uninitialized value", self.path)
                             }
                             // Other errors shouldn't be possible
                             _ => return Err(err),
diff --git a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
index 80e60dbb58a..f12753e5dca 100644
--- a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
+++ b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
@@ -62,7 +62,7 @@ LL | |
 LL | |     let uninit_len = MaybeUninit::<usize> { uninit: () };
 LL | |     mem::transmute((42, uninit_len))
 LL | | };
-   | |__^ type validation failed: encountered undefined pointer
+   | |__^ type validation failed: encountered uninitialized reference
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -130,7 +130,7 @@ LL | |
 LL | |     let uninit_len = MaybeUninit::<usize> { uninit: () };
 LL | |     mem::transmute((42, uninit_len))
 LL | | };
-   | |__^ type validation failed: encountered undefined pointer
+   | |__^ type validation failed: encountered uninitialized raw pointer
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/union-ice.stderr b/src/test/ui/consts/const-eval/union-ice.stderr
index 476f3651740..946c375ced7 100644
--- a/src/test/ui/consts/const-eval/union-ice.stderr
+++ b/src/test/ui/consts/const-eval/union-ice.stderr
@@ -27,7 +27,7 @@ LL | |         unsafe { UNION.field3 },
 ...  |
 LL | |     a: 42,
 LL | | };
-   | |__^ type validation failed: encountered undefined bytes at .b[1]
+   | |__^ type validation failed: encountered uninitialized value at .b[1]
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.