Resolve some review comments

src/librustc/middle/limits.rs

@@ -18,7 +18,7 @@ use rustc_data_structures::sync::Once;
 // `ensure_sufficient_stack`.
 const RED_ZONE: usize = 100 * 1024; // 100k
 
-// Ony the first stack that is pushed, grows exponentially (2^n * STACK_PER_RECURSION) from then
+// Only the first stack that is pushed, grows exponentially (2^n * STACK_PER_RECURSION) from then
 // on. This flag has performance relevant characteristics. Don't set it too high.
 const STACK_PER_RECURSION: usize = 1 * 1024 * 1024; // 1MB
 
@@ -27,7 +27,7 @@ const STACK_PER_RECURSION: usize = 1 * 1024 * 1024; // 1MB
 /// from this.
 ///
 /// Should not be sprinkled around carelessly, as it causes a little bit of overhead.
-pub fn ensure_sufficient_stack<R, F: FnOnce() -> R>(f: F) -> R {
+pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R {
     stacker::maybe_grow(RED_ZONE, STACK_PER_RECURSION, f)
 }
 

src/librustc_ast_lowering/expr.rs

@@ -1,7 +1,7 @@
 use super::{ImplTraitContext, LoweringContext, ParamMode, ParenthesizedGenericArgs};
 
-use rustc::bug;
 use rustc::middle::limits::ensure_sufficient_stack;
+use rustc::{bug, span_bug};
 use rustc_ast::ast::*;
 use rustc_ast::attr;
 use rustc_ast::ptr::P as AstP;
@@ -210,9 +210,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
             ExprKind::Yield(ref opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
             ExprKind::Err => hir::ExprKind::Err,
             ExprKind::Try(ref sub_expr) => self.lower_expr_try(e.span, sub_expr),
-
             ExprKind::ForLoop(..) | ExprKind::Paren(_) => {
-                span_bug!(e.span, "Should be handled by `lower_expr`")
+                span_bug!(e.span, "Should have been handled by `lower_expr`")
             }
             ExprKind::MacCall(_) => span_bug!(e.span, "Shouldn't exist here"),
         }

src/librustc_ast_lowering/pat.rs

@@ -85,7 +85,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 // If we reach here the `..` pattern is not semantically allowed.
                 self.ban_illegal_rest_pat(p.span)
             }
-            PatKind::Paren(_) => span_bug!(p.span, "Should be handled by `lower_pat`"),
+            PatKind::Paren(_) => span_bug!(p.span, "Should have been handled by `lower_pat`"),
             PatKind::MacCall(_) => span_bug!(p.span, "Shouldn't exist here"),
         }
     }