swift

0588b6db - [Type checker] Basic ambiguity resolution + diagnostics for dynamic replacement.

[Type checker] Basic ambiguity resolution + diagnostics for dynamic replacement. We weren't doing much validation when dynamically replacing storage declarations, and has an assert() that should be an error. Clean up this area a bit, dealing with simple ambiguities (i.e., there are two properties or subscripts with different type signatures; pick the matching one) and reporting an error when there is a true ambiguity. Fixes rdar://problem/46737657. (cherry picked from commit 5d968621d7aee9ef05aec54cdac4a75fe1798833)