1 files changed, 55 insertions, 0 deletions
diff --git a/src/macros.rs b/src/macros.rs
new file mode 100644
index 00000000..6aab95cf
--- /dev/null
+++ b/src/macros.rs
@@ -0,0 +1,55 @@
+//! Error handling.
+
+/// Create an error type.
+macro_rules! error_type {
+    (   // The variable used instead of self in functions
+        // followed by the error type things are happening on.
+        $var:ident: $err:ident,
+        // Optionally the name of a result type to generate.
+        $(res: $res:ident,)*
+        // A `Display` and `Debug` implementation.
+        show: $f:ident => $show:expr,
+        // Optionally a `source` function for the `std::error::Error` trait.
+        $(source: $source:expr,)*
+        // Any number of `From` implementations.
+        $(from: ($from:path, $conv:expr),)*
+    ) => {
+        // Possibly create a result type.
+        $(type $res<T> = std::result::Result<T, $err>;)*
+
+        impl std::fmt::Display for $err {
+            fn fmt(&self, $f: &mut std::fmt::Formatter) -> std::fmt::Result {
+                let $var = self;
+                $show
+            }
+        }
+
+        debug_display!($err);
+
+        impl std::error::Error for $err {
+            // The source method is only generated if an implementation was given.
+            $(fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+                let $var = self;
+                $source
+            })*
+        }
+
+        // Create any number of from implementations.
+        $(impl From<$from> for $err {
+            fn from($var: $from) -> $err {
+                $conv
+            }
+        })*
+    };
+}
+
+/// Create a `Debug` implementation from a display implementation.
+macro_rules! debug_display {
+    ($type:ident) => {
+        impl std::fmt::Debug for $type {
+            fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+                std::fmt::Display::fmt(self, f)
+            }
+        }
+    };
+}