Prevent deprecation warning for items deprecated in the future

Author: varkor

src/librustc/middle/stability.rs

@@ -559,9 +559,41 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         // Deprecated attributes apply in-crate and cross-crate.
         if let Some(id) = id {
             if let Some(depr_entry) = self.lookup_deprecation_entry(def_id) {
+                fn deprecation_in_effect(since: Option<&str>, rustc: Option<&str>) -> bool {
+                    fn parse_version(ver: &str) -> Vec<u32> {
+                        // We ignore non-integer components of the version (e.g. "nightly").
+                        ver.split(|c| c == '.' || c == '-').flat_map(|s| s.parse()).collect()
+                    }
+
+                    if since.is_none() || rustc.is_none() {
+                        // By default, a deprecation warning applies to
+                        // the current version of the compiler.
+                        true
+                    } else {
+                        let since: Vec<u32> = parse_version(since.unwrap());
+                        let rustc: Vec<u32> = parse_version(rustc.unwrap());
+                        // We simply treat invalid `since` attributes as relating to a previous
+                        // Rust version, thus always displaying the warning.
+                        if since.len() != 3 {
+                            return true;
+                        }
+                        since <= rustc
+                    }
+                }
+
+                // If the deprecation is scheduled for a future Rust
+                // version, then we should display no warning message.
+                let deprecated_in_future_version = if let Some(sym) = depr_entry.attr.since {
+                    let since = sym.as_str();
+                    !deprecation_in_effect(Some(since.as_ref()), option_env!("CFG_RELEASE"))
+                } else {
+                    false
+                };
+
                 let parent_def_id = self.hir.local_def_id(self.hir.get_parent(id));
-                let skip = self.lookup_deprecation_entry(parent_def_id)
-                    .map_or(false, |parent_depr| parent_depr.same_origin(&depr_entry));
+                let skip = deprecated_in_future_version ||
+                           self.lookup_deprecation_entry(parent_def_id)
+                               .map_or(false, |parent_depr| parent_depr.same_origin(&depr_entry));
                 if !skip {
                     lint_deprecated(def_id, id, depr_entry.attr.note);
                 }