feat: add deserializer-static-generics conditional compilation macro

2 files changed, 61 insertions, 2 deletions

diff --git a/src/deserializer/mod.rs b/src/deserializer/mod.rs
index 918136f..6a512dc 100644
--- a/src/deserializer/mod.rs
+++ b/src/deserializer/mod.rs
@@ -2,7 +2,7 @@
 use std::convert::Infallible;
 
 use crate::tagged::TagStart;
-use crate::util::trait_alias;
+use crate::util::{feature_alternate, trait_alias};
 use crate::DeserializeTagged;
 
 pub mod buffered;
@@ -278,3 +278,45 @@ macro_rules! impl_from_deserializer_error {
         }
     };
 }
+
+feature_alternate!(
+    feature = "deserializer-static-generics",
+    /// Conditional compilation based on whether or not the `deserializer-static-generics`
+    /// feature is enabled.
+    ///
+    /// # Examples
+    /// ```
+    /// use std::io::Cursor;
+    ///
+    /// use xml_stinks::xml_stinks_if_deserializer_static_generics;
+    /// use xml_stinks::deserializer::buffered::Buffered as BufferedDeserializer;
+    /// use xml_stinks::deserializer::Deserializer;
+    ///
+    /// fn do_something(bytes: &[u8])
+    /// {
+    ///     let deserializer = xml_stinks_if_deserializer_static_generics!(then {
+    ///         BufferedDeserializer::new(Cursor::new(bytes.to_vec()));
+    ///     } else {
+    ///         // This wouldn't compile if the deserializer-static-generics feature was
+    ///         // enabled
+    ///         BufferedDeserializer::new(bytes);
+    ///     });
+    ///
+    ///     // ...
+    /// }
+    /// ```
+    when_enabled =
+        #[macro_export]
+        macro_rules! xml_stinks_if_deserializer_static_generics {
+            (then { $($then: tt)* }$(else { $($else: tt)* })?) => {
+                $($then)*
+            };
+        },
+    when_disabled =
+        #[macro_export]
+        macro_rules! xml_stinks_if_deserializer_static_generics {
+            (then { $($then: tt)* }$(else { $($else: tt)* })?) => {
+                $($($else)*)?
+            };
+        }
+);
diff --git a/src/util.rs b/src/util.rs
index 78d2cd4..5c9ffb8 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -10,4 +10,21 @@ macro_rules! trait_alias {
     };
 }
 
-pub(crate) use trait_alias;
+macro_rules! feature_alternate {
+    (
+        feature = $feature: literal,
+        $(#[doc = $doc: literal])*
+        when_enabled = $when_enabled: item,
+        when_disabled = $when_disabled: item
+    ) => {
+        $(#[doc = $doc])*
+        #[cfg(feature = $feature)]
+        $when_enabled
+
+        $(#[doc = $doc])*
+        #[cfg(not(feature = $feature))]
+        $when_disabled
+    };
+}
+
+pub(crate) use {feature_alternate, trait_alias};