swift234

IRGen: Collect/emit nested generic substitutions.

Alter CalleeSource and Callee to keep their own internal vector of substitutions and concatentate multiple SpecializationExpr substitutions. Update EmitPolymorphicArguments::emit to emit arguments out of the substitution list based on the generic parameters of the current function type instead of assuming that the substitution list and generic parameter list match up.

Swift SVN r3937