Rollup merge of #79337 - LingMan:map, r=jyn514

Use Option::map instead of open coding it

r?  `@jonas-schievink` since you're frequently sniping these minor cleanups anyway.
`@rustbot` modify labels +C-cleanup  +T-compiler

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -1152,10 +1152,7 @@ impl<'ll> MemberDescription<'ll> {
                 self.size.bits(),
                 self.align.bits() as u32,
                 self.offset.bits(),
-                match self.discriminant {
-                    None => None,
-                    Some(value) => Some(cx.const_u64(value)),
-                },
+                self.discriminant.map(|v| cx.const_u64(v)),
                 self.flags,
                 self.type_metadata,
             )

compiler/rustc_middle/src/ty/sty.rs

@@ -1106,10 +1106,7 @@ impl<T> Binder<T> {
 
 impl<T> Binder<Option<T>> {
     pub fn transpose(self) -> Option<Binder<T>> {
-        match self.0 {
-            Some(v) => Some(Binder(v)),
-            None => None,
-        }
+        self.0.map(Binder)
     }
 }
 

compiler/rustc_typeck/src/check/demand.rs

@@ -810,10 +810,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // can be given the suggestion "u32::from(x) > y" rather than
                 // "x > y.try_into().unwrap()".
                 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
-                    match self.tcx.sess.source_map().span_to_snippet(expr.span).ok() {
-                        Some(src) => Some((expr, src)),
-                        None => None,
-                    }
+                    self.tcx
+                        .sess
+                        .source_map()
+                        .span_to_snippet(expr.span)
+                        .ok()
+                        .map(|src| (expr, src))
                 });
                 let (span, msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
                     (lhs_expr_and_src, exp_to_found_is_fallible)