fix typos in comments

Author: GoodDaisy

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -1010,7 +1010,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             // Just make this an efficient immediate.
             // Note that not calling `layout_of` here does have one real consequence:
             // if the type is too big, we'll only notice this when the local is actually initialized,
-            // which is a bit too late -- we should ideally notice this alreayd here, when the memory
+            // which is a bit too late -- we should ideally notice this already here, when the memory
             // is conceptually allocated. But given how rare that error is and that this is a hot function,
             // we accept this downside for now.
             Operand::Immediate(Immediate::Uninit)

library/core/src/num/mod.rs

@@ -114,7 +114,7 @@ macro_rules! midpoint_impl {
                       without modifying the original"]
         #[inline]
         pub const fn midpoint(self, rhs: $SelfT) -> $SelfT {
-            // Use the well known branchless algorthim from Hacker's Delight to compute
+            // Use the well known branchless algorithm from Hacker's Delight to compute
             // `(a + b) / 2` without overflowing: `((a ^ b) >> 1) + (a & b)`.
             ((self ^ rhs) >> 1) + (self & rhs)
         }

src/doc/unstable-book/src/compiler-flags/check-cfg.md

@@ -123,7 +123,7 @@ rustc --check-cfg 'cfg(is_embedded, has_feathers, values(any()))' \
 fn do_embedded() {}         // and because names exhaustiveness was not disabled
 
 #[cfg(has_feathers)]        // This is expected as "has_feathers" was provided in cfg()
-fn do_features() {}         // and because names exhaustiveness was not disbaled
+fn do_features() {}         // and because names exhaustiveness was not disabled
 
 #[cfg(has_feathers = "zapping")] // This is expected as "has_feathers" was provided in cfg()
                                  // and because no value checking was enable for "has_feathers"