new RFC: static_lifetime_in_statics

text/0000-static.md

@@ -0,0 +1,70 @@
+- Feature Name: static_lifetime_in_statics
+- Start Date: 2016-05-20
+- RFC PR: (leave this empty)
+- Rust Issue: (leave this empty)
+
+# Summary
+[summary]: #summary
+
+Let's default lifetimes in static and const declarations to `'static`.
+
+# Motivation
+[motivation]: #motivation
+
+Currently, having references in `static` and `const` declarations is cumbersome 
+due to having to explicitly write `&'static ..`. On the other hand anything but 
+static is likely either useless, unsound or both. Also the long lifetime name 
+causes substantial rightwards drift, which makes it hard to format the code 
+to be visually appealing.
+
+For example, having a `'static` default for lifetimes would turn this:
+```
+static my_awesome_tables: &'static [&'static HashMap<Cow<'static, str>, u32>] = ..
+```
+into this:
+```
+static my_awesome_table: &[&HashMap<Cow<str>, u32>] = ..
+```
+
+The type declaration still causes some rightwards drift, but at least all the
+contained information is useful.
+
+# Detailed design
+[design]: #detailed-design
+
+The same default that RFC #599 sets up for trait object is to be used for 
+statics and const declarations. In those declarations, the compiler will assume 
+`'static` when a lifetime is not explicitly given in both refs and generics.
+
+Note that this RFC does not forbid writing the lifetimes, it only sets a 
+default when no is given. Thus the change is unlikely to cause any breakage and 
+should be deemed backwards-compatible. It's also very unlikely that 
+implementing this RFC will restrict our design space for `static` and `const` 
+definitions down the road.
+
+# Drawbacks
+[drawbacks]: #drawbacks
+
+There are no known drawbacks to this change.
+
+# Alternatives
+[alternatives]: #alternatives
+
+* Leave everything as it is. Everyone using static references is annoyed by 
+having to add `'static` without any value to readability. People will resort to 
+writing macros if they have many resources.
+* Write the aforementioned macro. This is inferior in terms of UX. Depending on
+the implementation it may or may not be possible to default lifetimes in
+generics.
+* Infer types for statics. The absence of types makes it harder to reason about
+the code, so even if type inference for statics was to be implemented, 
+defaulting lifetimes would have the benefit of pulling the cost-benefit 
+relation in the direction of more explicit code. Thus it is advisable to 
+implement this change even with the possibility of implementing type inference 
+later.
+
+# Unresolved questions
+[unresolved]: #unresolved-questions
+
+* Does this change requires changing the grammar?
+* Are there other Rust-code handling programs that need to be updated?