codegen/statics: forward #[cfg] attributes

fixes #110

macros/src/codegen.rs

@@ -1808,14 +1808,17 @@ fn mk_locals(locals: &HashMap<Ident, Static>, once: bool) -> proc_macro2::TokenS
         .iter()
         .map(|(name, static_)| {
             let attrs = &static_.attrs;
+            let cfgs = &static_.cfgs;
             let expr = &static_.expr;
             let ident = name;
             let ty = &static_.ty;
 
             quote!(
                 #[allow(non_snake_case)]
+                #(#cfgs)*
                 let #ident: &#lt mut #ty = {
                     #(#attrs)*
+                    #(#cfgs)*
                     static mut #ident: #ty = #expr;
 
                     unsafe { &mut #ident }

macros/src/syntax.rs

@@ -1003,6 +1003,9 @@ fn parse_args(input: ParseStream, accept_capacity: bool) -> parse::Result<TaskAr
 }
 
 pub struct Static {
+    /// `#[cfg]` attributes
+    pub cfgs: Vec<Attribute>,
+    /// Attributes that are not `#[cfg]`
     pub attrs: Vec<Attribute>,
     pub ty: Box<Type>,
     pub expr: Box<Expr>,
@@ -1020,10 +1023,13 @@ impl Static {
                 ));
             }
 
+            let (cfgs, attrs) = extract_cfgs(item.attrs);
+
             statics.insert(
                 item.ident,
                 Static {
-                    attrs: item.attrs,
+                    cfgs,
+                    attrs,
                     ty: item.ty,
                     expr: item.expr,
                 },
@@ -1150,6 +1156,21 @@ fn eq(attr: &Attribute, name: &str) -> bool {
     }
 }
 
+fn extract_cfgs(attrs: Vec<Attribute>) -> (Vec<Attribute>, Vec<Attribute>) {
+    let mut cfgs = vec![];
+    let mut not_cfgs = vec![];
+
+    for attr in attrs {
+        if eq(&attr, "cfg") {
+            cfgs.push(attr);
+        } else {
+            not_cfgs.push(attr);
+        }
+    }
+
+    (cfgs, not_cfgs)
+}
+
 /// Extracts `static mut` vars from the beginning of the given statements
 fn extract_statics(stmts: Vec<Stmt>) -> (Statics, Vec<Stmt>) {
     let mut istmts = stmts.into_iter();