Rollup merge of #126159 - RalfJung:scalarint-size-mismatch, r=oli-obk

ScalarInt: size mismatches are a bug, do not delay the panic

Cc [Zulip](https://rust-lang.zulipchat.com/#narrow/stream/146212-t-compiler.2Fconst-eval/topic/Why.20are.20ScalarInt.20to.20iN.2FuN.20methods.20fallible.3F)

r? ``@oli-obk``

src/intrinsics/simd.rs

@@ -645,8 +645,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 for i in 0..dest_len {
                     let src_index: u64 = index[usize::try_from(i).unwrap()]
                         .unwrap_leaf()
-                        .try_to_u32()
-                        .unwrap()
+                        .to_u32()
                         .into();
                     let dest = this.project_index(&dest, i)?;
 

src/shims/unix/socket.rs

@@ -51,9 +51,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         let fds = &mut this.machine.fds;
         let sv0 = fds.insert_fd(FileDescriptor::new(SocketPair));
-        let sv0 = Scalar::try_from_int(sv0, sv.layout.size).unwrap();
+        let sv0 = Scalar::from_int(sv0, sv.layout.size);
         let sv1 = fds.insert_fd(FileDescriptor::new(SocketPair));
-        let sv1 = Scalar::try_from_int(sv1, sv.layout.size).unwrap();
+        let sv1 = Scalar::from_int(sv1, sv.layout.size);
 
         this.write_scalar(sv0, &sv)?;
         this.write_scalar(sv1, &sv.offset(sv.layout.size, sv.layout, this)?)?;