Sema: Replace trivial FunctionType::getOld() with decomposeInput()

These usages of getOld() always pass in a ParenType or TupleType
as the input type, so there's no conceptual difficulty with
using the new representation instead.

Note that eventually we want to remove decomposeInput() too.
However until ApplyExpr and friends are redesigned to directly
hold multiple arguments instead of a single argument
sub-expression that is a ParenExpr or TupleExpr, we don't
have a good way to avoid building a tuple type and decomposing
it in this one case.

Instead just inline what getOld() does so we can move forward.

Author: slavapestov

lib/Sema/CSGen.cpp

@@ -1530,9 +1530,16 @@ namespace {
           CS.getConstraintLocator(expr, ConstraintLocator::RValueAdjustment));
 
         // The function/enum case must be callable with the given argument.
-        auto funcTy = FunctionType::getOld(CS.getType(arg), outputTy);
-        CS.addConstraint(ConstraintKind::ApplicableFunction, funcTy,
-          memberTy,
+
+        // FIXME: Redesign the AST so that an UnresolvedMemberExpr directly
+        // stores a list of arguments together with their inout-ness, instead of
+        // a single ParenExpr or TupleExpr argument.
+        SmallVector<AnyFunctionType::Param, 8> params;
+        AnyFunctionType::decomposeInput(CS.getType(arg), params);
+
+        CS.addConstraint(ConstraintKind::ApplicableFunction,
+                         FunctionType::get(params, outputTy),
+                         memberTy,
           CS.getConstraintLocator(expr, ConstraintLocator::ApplyFunction));
 
         return baseTy;
@@ -2530,11 +2537,15 @@ namespace {
       FunctionType::ExtInfo extInfo;
       if (isa<ClosureExpr>(fnExpr->getSemanticsProvidingExpr()))
         extInfo = extInfo.withNoEscape();
-      
-      auto funcTy = FunctionType::getOld(CS.getType(expr->getArg()), outputTy,
-                                         extInfo);
 
-      CS.addConstraint(ConstraintKind::ApplicableFunction, funcTy,
+      // FIXME: Redesign the AST so that an ApplyExpr directly stores a list of
+      // arguments together with their inout-ness, instead of a single
+      // ParenExpr or TupleExpr.
+      SmallVector<AnyFunctionType::Param, 8> params;
+      AnyFunctionType::decomposeInput(CS.getType(expr->getArg()), params);
+
+      CS.addConstraint(ConstraintKind::ApplicableFunction,
+                       FunctionType::get(params, outputTy, extInfo),
                        CS.getType(expr->getFn()),
         CS.getConstraintLocator(expr, ConstraintLocator::ApplyFunction));