[NFC] Rename isPackExpansion -> isOrigPackExpansion for clarity

Author: rjmccall

include/swift/SIL/AbstractionPatternGenerators.h

@@ -51,7 +51,7 @@ class FunctionParamGenerator {
   unsigned substParamIndex = 0;
 
   /// The number of subst parameters corresponding to the current
-  /// subst parameter.
+  /// orig parameter.
   unsigned numSubstParamsForOrigParam;
 
   /// Whether the orig function type is opaque, i.e. does not permit us to
@@ -125,7 +125,7 @@ class FunctionParamGenerator {
   }
 
   /// Return whether the current orig parameter type is a pack expansion.
-  bool isPackExpansion() const {
+  bool isOrigPackExpansion() const {
     assert(!isFinished());
     return origParamIsExpansion;
   }

lib/SIL/IR/AbstractionPattern.cpp

@@ -2236,7 +2236,7 @@ class SubstFunctionTypePatternVisitor
 
     pattern.forEachFunctionParam(func.getParams(), /*ignore self*/ false,
                                  [&](FunctionParamGenerator &param) {
-      if (!param.isPackExpansion()) {
+      if (!param.isOrigPackExpansion()) {
         auto newParamTy = visit(param.getSubstParams()[0].getParameterType(),
                                 param.getOrigType());
         addParam(param.getOrigFlags(), newParamTy);

lib/SIL/IR/SILFunctionType.cpp

@@ -1576,7 +1576,7 @@ class DestructureInputs {
       // If the parameter is not a pack expansion, just pull off the
       // next parameter and destructure it in parallel with the abstraction
       // pattern for the type.
-      if (!param.isPackExpansion()) {
+      if (!param.isOrigPackExpansion()) {
         visit(param.getOrigType(), param.getSubstParams()[0],
               /*forSelf*/false);
         return;

lib/SILGen/FunctionInputGenerator.h

@@ -89,7 +89,7 @@ class FunctionInputGenerator {
   /// Ready the current orig parameter.
   void readyOrigParameter() {
     substParamIndex = 0;
-    if (origParam.isPackExpansion()) {
+    if (origParam.isOrigPackExpansion()) {
       // The pack value exists in the lowered parameters and must be
       // claimed whether it contains formal parameters or not.
       packValue = inputs.claimNext();
@@ -125,7 +125,7 @@ class FunctionInputGenerator {
   }
 
   bool isOrigPackExpansion() const {
-    return origParam.isPackExpansion();
+    return origParam.isOrigPackExpansion();
   }
 
   AbstractionPattern getOrigType() const {

lib/SILGen/SILGenPoly.cpp

@@ -1094,7 +1094,7 @@ class TranslateArguments {
       // output type, it corresponds to N formal parameters in the
       // substituted output type.  translateToPackParam will pull off
       // N substituted formal parameters from the input type.
-      if (outputParams.isPackExpansion()) {
+      if (outputParams.isOrigPackExpansion()) {
         auto outputPackParam = claimNextOutputType();
         auto output =
           translateToPackParam(inputParams,