use new try_from methods

src/helpers.rs

@@ -501,35 +501,22 @@ fn bytes_to_os_str<'tcx, 'a>(bytes: &'a [u8]) -> InterpResult<'tcx, &'a OsStr> {
     Ok(&OsStr::new(s))
 }
 
-// FIXME: change `ImmTy::from_int` so it returns an `InterpResult` instead and remove this
-// function.
 pub fn immty_from_int_checked<'tcx>(
     int: impl Into<i128>,
     layout: TyLayout<'tcx>,
 ) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
     let int = int.into();
-    // If `int` does not fit in `size` bits, we error instead of letting
-    // `ImmTy::from_int` panic.
-    let size = layout.size;
-    let truncated = truncate(int as u128, size);
-    if sign_extend(truncated, size) as i128 != int {
-        throw_unsup_format!("Signed value {:#x} does not fit in {} bits", int, size.bits())
-    }
-    Ok(ImmTy::from_int(int, layout))
+    Ok(ImmTy::try_from_int(int, layout).ok_or_else(||
+        err_unsup_format!("Signed value {:#x} does not fit in {} bits", int, layout.size.bits())
+    )?)
 }
 
-// FIXME: change `ImmTy::from_uint` so it returns an `InterpResult` instead and remove this
-// function.
 pub fn immty_from_uint_checked<'tcx>(
     int: impl Into<u128>,
     layout: TyLayout<'tcx>,
 ) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
     let int = int.into();
-    // If `int` does not fit in `size` bits, we error instead of letting
-    // `ImmTy::from_int` panic.
-    let size = layout.size;
-    if truncate(int, size) != int {
-        throw_unsup_format!("Unsigned value {:#x} does not fit in {} bits", int, size.bits())
-    }
-    Ok(ImmTy::from_uint(int, layout))
+    Ok(ImmTy::try_from_uint(int, layout).ok_or_else(||
+        err_unsup_format!("Signed value {:#x} does not fit in {} bits", int, layout.size.bits())
+    )?)
 }