All refutable patterns and function parameters marked with 'var'
is now an error.
- Using explicit 'let' keyword on function parameters causes a warning.
- Don't suggest making function parameters mutable
- Remove uses in the standard library
- Update tests
rdar://problem/23378003
The culprit happened to be a type representation cloner for tuple type
representations that didn't actually clone anything. Introduce an
AST-level verifier that makes sure we catch any archetypes that slip
into interface types earlier in the future.
Fixes rdar://problem/18796397 and the three dupes I've found so far.
Swift SVN r28080