[ConstraintSystem] Allow type variables for pack expansion patterns to bind

to noescape.

Author: hborla

lib/Sema/CSGen.cpp

@@ -3057,6 +3057,7 @@ namespace {
           CS.getConstraintLocator(expr, ConstraintLocator::PackExpansionPattern);
       auto patternTy = CS.createTypeVariable(patternLoc,
                                              TVO_CanBindToPack |
+                                             TVO_CanBindToNoEscape |
                                              TVO_CanBindToHole);
       auto elementResultType = CS.getType(expr->getPatternExpr());
       CS.addConstraint(ConstraintKind::PackElementOf, elementResultType,

test/Constraints/pack-expansion-expressions.swift

@@ -196,3 +196,9 @@ func test_pack_expansion_materialization_from_lvalue_base() {
     }
   }
 }
+
+func takesFunctionPack<each T, R>(functions: repeat ((each T) -> R)) {}
+
+func forwardFunctionPack<each T>(functions: repeat (each T) -> Bool) {
+  takesFunctionPack(functions: repeat each functions)
+}