Use assert_usize instead of unwrap_usize in several places

Author: varkor

src/librustc_codegen_llvm/debuginfo/metadata.rs

@@ -342,9 +342,7 @@ fn fixed_vec_metadata(
     let (size, align) = cx.size_and_align_of(array_or_slice_type);
 
     let upper_bound = match array_or_slice_type.sty {
-        ty::Array(_, len) => {
-            len.unwrap_usize(cx.tcx) as c_longlong
-        }
+        ty::Array(_, len) => len.unwrap_usize(cx.tcx) as c_longlong,
         _ => -1
     };
 

src/librustc_mir/borrow_check/places_conflict.rs

@@ -332,8 +332,8 @@ fn place_base_conflict<'a, 'gcx: 'tcx, 'tcx>(
                 },
                 (StaticKind::Promoted(promoted_1), StaticKind::Promoted(promoted_2)) => {
                     if promoted_1 == promoted_2 {
-                        if let ty::Array(_, size) = s1.ty.sty {
-                            if size.unwrap_usize(tcx) == 0 {
+                        if let ty::Array(_, len) = s1.ty.sty {
+                            if let Some(0) = len.assert_usize(tcx) {
                                 // Ignore conflicts with promoted [T; 0].
                                 debug!("place_element_conflict: IGNORE-LEN-0-PROMOTED");
                                 return Overlap::Disjoint;