Merge pull request #1373 from akoshelev/step-index

Extend the compact gate implementation to provide `index` method

ipa-step-derive/src/lib.rs

@@ -165,6 +165,18 @@ fn derive_gate_impl(ast: &DeriveInput) -> TokenStream {
                 <Self as ::std::fmt::Display>::fmt(self, f)
             }
         }
+
+        impl #name {
+            /// Returns the current index. It matches the index of the latest step
+            /// this gate has been narrowed to.
+            ///
+            /// If gate hasn't been narrowed yet, it returns the index of the default value.
+            #[must_use]
+            pub fn index(&self) -> ::ipa_step::CompactGateIndex {
+                self.0
+            }
+        }
+
     };
 
     // This environment variable is set by build scripts,

ipa-step-test/src/lib.rs

@@ -17,22 +17,35 @@ mod tests {
 
     #[test]
     fn narrows() {
+        assert_eq!(ComplexGate::default().index(), 0);
         assert_eq!(ComplexGate::default().as_ref(), "/");
         assert_eq!(
             ComplexGate::default().narrow(&ComplexStep::One).as_ref(),
             "/one"
         );
+        assert_eq!(ComplexGate::default().narrow(&ComplexStep::One).index(), 1,);
         assert_eq!(
             ComplexGate::default().narrow(&ComplexStep::Two(2)).as_ref(),
             "/two2"
         );
+        assert_eq!(
+            ComplexGate::default().narrow(&ComplexStep::Two(2)).index(),
+            10,
+        );
         assert_eq!(
             ComplexGate::default()
                 .narrow(&ComplexStep::Two(2))
                 .narrow(&BasicStep::One)
                 .as_ref(),
             "/two2/one"
         );
+        assert_eq!(
+            ComplexGate::default()
+                .narrow(&ComplexStep::Two(2))
+                .narrow(&BasicStep::One)
+                .index(),
+            11,
+        );
         assert_eq!(
             ComplexGate::from("/two2/one"),
             ComplexGate::default()