swift

669a2ce9 - [CS] Sink placeholder handling logic into `Solution::simplifyType`

[CS] Sink placeholder handling logic into `Solution::simplifyType` Move the logic from `FailureDiagnostic::resolveType` into `Solution::simplifyType` to allow completion to use it too. While here, also handle cases where the placeholder is from a different member of the equivalence class to the generic parameter.