Always generate Error::backtrace.

Author: Yamakaky

src/error_chain.rs

@@ -86,6 +86,11 @@ macro_rules! error_chain_processed {
             pub fn iter(&self) -> $crate::ErrorChainIter {
                 $crate::ErrorChainIter(Some(self))
             }
+
+            /// Returns the backtrace associated with this error.
+            pub fn backtrace(&self) -> Option<&$crate::Backtrace> {
+                self.state.backtrace()
+            }
         }
 
         impl ::std::error::Error for $error_name {
@@ -308,13 +313,6 @@ macro_rules! impl_error {
     ($error_name: ident
      $error_kind_name: ident
      $([$link_error_path: path, $(#[$meta_links: meta])*])*) => {
-        impl $error_name {
-            /// Returns the backtrace associated with this error.
-            pub fn backtrace(&self) -> Option<&$crate::Backtrace> {
-                self.state.backtrace.as_ref().map(|v| &**v)
-            }
-        }
-
         impl $crate::ChainedError for $error_name {
             type ErrorKind = $error_kind_name;
 

src/lib.rs

@@ -261,6 +261,9 @@ use std::sync::Arc;
 
 #[cfg(feature = "backtrace")]
 pub use backtrace::Backtrace;
+#[cfg(not(feature = "backtrace"))]
+/// Dummy type used when the `backtrace` feature is disabled.
+pub type Backtrace = ();
 
 #[macro_use]
 mod quick_error;
@@ -371,6 +374,17 @@ impl Default for State {
     }
 }
 
+impl State {
+    /// Returns the inner backtrace if present.
+    pub fn backtrace(&self) -> Option<&Backtrace> {
+        #[cfg(feature = "backtrace")]
+        let b = self.backtrace.as_ref().map(|v| &**v);
+        #[cfg(not(feature = "backtrace"))]
+        let b = None;
+        b
+    }
+}
+
 /// This modules show an example of code generated by the macro. IT MUST NOT BE
 /// USED OUTSIDE THIS CRATE.
 ///