openpgp: Move destructures_to macro to macros.rs

1 files changed, 20 insertions, 0 deletions

diff --git a/openpgp/src/macros.rs b/openpgp/src/macros.rs
index 20aaa6e5..50be3afa 100644
--- a/openpgp/src/macros.rs
+++ b/openpgp/src/macros.rs
@@ -1,5 +1,25 @@
 use std::cmp;
 
+// Turns an `if let` into an expression so that it is possible to do
+// things like:
+//
+// ```rust,nocompile
+// if destructures_to(Foo::Bar(_) = value)
+//    || destructures_to(Foo::Bam(_) = value) { ... }
+// ```
+macro_rules! destructures_to {
+    ( $error: pat = $expr:expr ) => {
+        {
+            let x = $expr;
+            if let $error = x {
+                true
+            } else {
+                false
+            }
+        }
+    };
+}
+
 macro_rules! trace {
     ( $TRACE:expr, $fmt:expr, $($pargs:expr),* ) => {
         if $TRACE {