Use if-let guards in the codebase

compiler/rustc_parse/src/validate_attr.rs

@@ -24,16 +24,15 @@ pub fn check_meta(sess: &ParseSess, attr: &Attribute) {
         Some((name, _, template, _)) if name != sym::rustc_dummy => {
             check_builtin_attribute(sess, attr, name, template)
         }
-        _ => {
-            if let MacArgs::Eq(..) = attr.get_normal_item().args {
-                // All key-value attributes are restricted to meta-item syntax.
-                parse_meta(sess, attr)
-                    .map_err(|mut err| {
-                        err.emit();
-                    })
-                    .ok();
-            }
+        _ if let MacArgs::Eq(..) = attr.get_normal_item().args => {
+            // All key-value attributes are restricted to meta-item syntax.
+            parse_meta(sess, attr)
+                .map_err(|mut err| {
+                    err.emit();
+                })
+                .ok();
         }
+        _ => {}
     }
 }