Merge pull request #183 from JasperDeSutter/patch-1

Make ensure! macro work with opaque error types

src/lib.rs

@@ -151,7 +151,7 @@ use std::error;
 macro_rules! ensure {
     ($predicate:expr, $context_selector:expr) => {
         if !$predicate {
-            return $context_selector.fail();
+            return $context_selector.fail().map_err(core::convert::Into::into);
         }
     };
 }

tests/opaque.rs

@@ -1,5 +1,5 @@
 mod inner {
-    use snafu::Snafu;
+    use snafu::{ensure, Snafu};
 
     #[derive(Debug, Snafu)]
     pub struct Error(InnerError);
@@ -8,6 +8,16 @@ mod inner {
         Ok(a()? + b()?)
     }
 
+    pub fn not_positive(value: i32) -> Result<i32, Error> {
+        ensure!(value < 1, TooBig { count: value });
+        Ok(value)
+    }
+
+    pub fn boxed_inner(value: i32) -> Result<i32, Box<dyn std::error::Error>> {
+        ensure!(value < 1, TooBig { count: value });
+        Ok(value)
+    }
+
     #[derive(Debug, Snafu)]
     enum InnerError {
         #[snafu(display = r#"("The value {} is too big", count)"#)]
@@ -30,3 +40,19 @@ fn implements_error() {
     let e = inner::api().unwrap_err();
     assert!(e.to_string().contains("too big"));
 }
+
+#[test]
+fn ensure_opaque() {
+    assert!(inner::not_positive(-1).is_ok());
+
+    let e = inner::not_positive(2).unwrap_err();
+    assert!(e.to_string().contains("too big"));
+}
+
+#[test]
+fn ensure_boxed() {
+    assert!(inner::boxed_inner(-1).is_ok());
+
+    let e = inner::boxed_inner(2).unwrap_err();
+    assert!(e.to_string().contains("too big"));
+}