Auto merge of #113677 - bryangarza:unevaluated-const-ice_issue-110892, r=davidtwco

Safe Transmute: Fix ICE (due to UnevaluatedConst)

This patch updates the code that looks at the `Assume` type when evaluating if transmutation is possible. An ICE was being triggered in the case that the `Assume` parameter contained an unevaluated const (in this test case, due to a function with missing parameter names).

Fixes #110892

2 files changed, 76 insertions, 0 deletions

diff --git a/tests/ui/transmutability/issue-110892.rs b/tests/ui/transmutability/issue-110892.rs
new file mode 100644
index 00000000000..ce926b39996
--- /dev/null
+++ b/tests/ui/transmutability/issue-110892.rs
@@ -0,0 +1,40 @@
+// check-fail
+#![feature(generic_const_exprs, transmutability)]
+#![allow(incomplete_features)]
+
+mod assert {
+    use std::mem::{Assume, BikeshedIntrinsicFrom};
+
+    pub fn is_transmutable<
+        Src,
+        Dst,
+        Context,
+        const ASSUME_ALIGNMENT: bool,
+        const ASSUME_LIFETIMES: bool,
+        const ASSUME_SAFETY: bool,
+        const ASSUME_VALIDITY: bool,
+    >()
+    where
+        Dst: BikeshedIntrinsicFrom<
+            Src,
+            Context,
+            { from_options(ASSUME_ALIGNMENT, ASSUME_LIFETIMES, ASSUME_SAFETY, ASSUME_VALIDITY) }
+        >,
+    {}
+
+    // This should not cause an ICE
+    const fn from_options(
+        , //~ ERROR expected parameter name, found `,`
+        , //~ ERROR expected parameter name, found `,`
+        , //~ ERROR expected parameter name, found `,`
+        , //~ ERROR expected parameter name, found `,`
+    ) -> Assume {} //~ ERROR mismatched types
+}
+
+fn main() {
+    struct Context;
+    #[repr(C)] struct Src;
+    #[repr(C)] struct Dst;
+
+    assert::is_transmutable::<Src, Dst, Context, false, false, { true }, false>();
+}
diff --git a/tests/ui/transmutability/issue-110892.stderr b/tests/ui/transmutability/issue-110892.stderr
new file mode 100644
index 00000000000..13654307aee
--- /dev/null
+++ b/tests/ui/transmutability/issue-110892.stderr
@@ -0,0 +1,36 @@
+error: expected parameter name, found `,`
+  --> $DIR/issue-110892.rs:27:9
+   |
+LL |         ,
+   |         ^ expected parameter name
+
+error: expected parameter name, found `,`
+  --> $DIR/issue-110892.rs:28:9
+   |
+LL |         ,
+   |         ^ expected parameter name
+
+error: expected parameter name, found `,`
+  --> $DIR/issue-110892.rs:29:9
+   |
+LL |         ,
+   |         ^ expected parameter name
+
+error: expected parameter name, found `,`
+  --> $DIR/issue-110892.rs:30:9
+   |
+LL |         ,
+   |         ^ expected parameter name
+
+error[E0308]: mismatched types
+  --> $DIR/issue-110892.rs:31:10
+   |
+LL |     const fn from_options(
+   |              ------------ implicitly returns `()` as its body has no tail or `return` expression
+...
+LL |     ) -> Assume {}
+   |          ^^^^^^ expected `Assume`, found `()`
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0308`.