feature guard rather than option

src/codegen/mod.rs

@@ -2111,7 +2111,7 @@ impl MethodCodegen for Method {
 #[derive(Copy, Clone)]
 enum EnumVariation {
     Rust,
-    Bitfield { use_associated_consts: bool },
+    Bitfield,
     Consts,
     ModuleConsts
 }
@@ -2153,7 +2153,6 @@ enum EnumBuilder<'a> {
     Bitfield {
         codegen_depth: usize,
         canonical_name: &'a str,
-        use_associated_consts: bool,
         tokens: quote::Tokens,
     },
     Consts {
@@ -2190,11 +2189,10 @@ impl<'a> EnumBuilder<'a> {
         let ident = quote::Ident::new(name);
 
         match enum_variation {
-            EnumVariation::Bitfield { use_associated_consts, .. } => {
+            EnumVariation::Bitfield => {
                 EnumBuilder::Bitfield {
                     codegen_depth: enum_codegen_depth,
                     canonical_name: name,
-                    use_associated_consts,
                     tokens: quote! {
                         #( #attrs )*
                         pub struct #ident (pub #repr);
@@ -2280,8 +2278,8 @@ impl<'a> EnumBuilder<'a> {
                 }
             }
 
-            EnumBuilder::Bitfield { canonical_name, use_associated_consts, .. } => {
-                if use_associated_consts {
+            EnumBuilder::Bitfield { canonical_name, .. } => {
+                if ctx.options().rust_features().associated_const {
                     let enum_ident = ctx.rust_ident(canonical_name);
                     let variant_ident = ctx.rust_ident(variant_name);
                     result.push(quote! {
@@ -2493,9 +2491,7 @@ impl CodeGenerator for Enum {
         let variation = if self.is_constified_enum_module(ctx, item) {
             EnumVariation::ModuleConsts
         } else if self.is_bitfield(ctx, item) {
-            EnumVariation::Bitfield {
-                use_associated_consts: ctx.options().use_associated_consts
-            }
+            EnumVariation::Bitfield
         } else if self.is_rustified_enum(ctx, item) {
             EnumVariation::Rust
         } else {

src/features.rs

@@ -90,6 +90,8 @@ macro_rules! rust_target_base {
             => Stable_1_0 => 1.0;
             /// Rust stable 1.19
             => Stable_1_19 => 1.19;
+            /// Rust stable 1.20
+            => Stable_1_20 => 1.20;
             /// Rust stable 1.21
             => Stable_1_21 => 1.21;
             /// Rust stable 1.25
@@ -142,6 +144,8 @@ rust_feature_def!(
     => builtin_clone_impls;
     /// repr(align) https://github.com/rust-lang/rust/pull/47006
     => repr_align;
+    /// associated constants https://github.com/rust-lang/rust/issues/29646
+    => associated_const;
 );
 
 impl From<RustTarget> for RustFeatures {
@@ -152,6 +156,10 @@ impl From<RustTarget> for RustFeatures {
             features.untagged_union = true;
         }
 
+        if rust_target >= RustTarget::Stable_1_20 {
+            features.associated_const = true;
+        }
+
         if rust_target >= RustTarget::Stable_1_21 {
             features.builtin_clone_impls = true;
         }

src/lib.rs

@@ -1235,12 +1235,6 @@ impl Builder {
         self.options.no_hash_types.insert(arg.into());
         self
     }
-
-    /// Use associated constants for bitfields.
-    pub fn use_associated_consts(mut self, doIt: bool) -> Builder {
-        self.options.use_associated_consts = doIt;
-        self
-    }
 }
 
 /// Configuration options for generated bindings.
@@ -1437,9 +1431,6 @@ struct BindgenOptions {
 
     /// The set of types that we should not derive `Hash` for.
     no_hash_types: RegexSet,
-
-    /// Whether to generated associated constants for bitfields.
-    use_associated_consts: bool,
 }
 
 /// TODO(emilio): This is sort of a lie (see the error message that results from
@@ -1534,7 +1525,6 @@ impl Default for BindgenOptions {
             no_partialeq_types: Default::default(),
             no_copy_types: Default::default(),
             no_hash_types: Default::default(),
-            use_associated_consts: false,
         }
     }
 }