Test validity of pattern types

Author: oli-obk

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -4,6 +4,7 @@
 //! That's useful because it means other passes (e.g. promotion) can rely on `const`s
 //! to be const-safe.
 
+use std::assert_matches::assert_matches;
 use std::borrow::Cow;
 use std::fmt::Write;
 use std::hash::Hash;
@@ -1240,6 +1241,17 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
                     self.visit_field(val, 0, &self.ecx.project_index(val, 0)?)?;
                 }
             }
+            ty::Pat(_base, pat) => {
+                // When you extend this match, make sure to also add tests to
+                // tests/ui/type/pattern_types/validity.rs((
+                match **pat {
+                    // Range patterns are precisely reflected into `valid_range` and thus
+                    // handled fully by `visit_scalar` (called below).
+                    ty::PatternKind::Range { .. } => {
+                        assert_matches!(val.layout.backend_repr, BackendRepr::Scalar(_));
+                    },
+                }
+            }
             _ => {
                 // default handler
                 try_validation!(

tests/ui/type/pattern_types/validity.rs

@@ -0,0 +1,27 @@
+//! Check that pattern types have their validity checked
+
+#![feature(pattern_types)]
+#![feature(pattern_type_macro)]
+
+use std::pat::pattern_type;
+
+const BAD: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(0) };
+//~^ ERROR: it is undefined behavior to use this value
+
+const BAD_UNINIT: pattern_type!(u32 is 1..) =
+    //~^ ERROR: evaluation of constant value failed
+    unsafe { std::mem::transmute(std::mem::MaybeUninit::<u32>::uninit()) };
+
+const BAD_PTR: pattern_type!(usize is 1..) = unsafe { std::mem::transmute(&42) };
+//~^ ERROR: evaluation of constant value failed
+
+const BAD_AGGREGATE: (pattern_type!(u32 is 1..), u32) = (unsafe { std::mem::transmute(0) }, 0);
+//~^ ERROR: it is undefined behavior to use this value
+
+struct Foo(Bar);
+struct Bar(pattern_type!(u32 is 1..));
+
+const BAD_FOO: Foo = Foo(Bar(unsafe { std::mem::transmute(0) }));
+//~^ ERROR: it is undefined behavior to use this value
+
+fn main() {}

tests/ui/type/pattern_types/validity.stderr

@@ -0,0 +1,51 @@
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/validity.rs:8:1
+   |
+LL | const BAD: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(0) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0, but expected something greater or equal to 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.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               00 00 00 00                                     │ ....
+           }
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/validity.rs:11:1
+   |
+LL | const BAD_UNINIT: pattern_type!(u32 is 1..) =
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ using uninitialized data, but this operation requires initialized memory
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/validity.rs:15:1
+   |
+LL | const BAD_PTR: pattern_type!(usize is 1..) = unsafe { std::mem::transmute(&42) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unable to turn pointer into integer
+   |
+   = help: this code performed an operation that depends on the underlying bytes representing a pointer
+   = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/validity.rs:18:1
+   |
+LL | const BAD_AGGREGATE: (pattern_type!(u32 is 1..), u32) = (unsafe { std::mem::transmute(0) }, 0);
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .0: encountered 0, but expected something greater or equal to 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.
+   = note: the raw bytes of the constant (size: 8, align: 4) {
+               00 00 00 00 00 00 00 00                         │ ........
+           }
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/validity.rs:24:1
+   |
+LL | const BAD_FOO: Foo = Foo(Bar(unsafe { std::mem::transmute(0) }));
+   | ^^^^^^^^^^^^^^^^^^ constructing invalid value at .0.0: encountered 0, but expected something greater or equal to 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.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               00 00 00 00                                     │ ....
+           }
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0080`.