Fix <rdar://problem/22000564> Crash on Subscript taking a tuple argument list

by changing buildSubscriptIndexReference to work solely in terms of the parameter
pattern of the subscript, instead of trying to walk the index type in parallel to
extract parameter labels.

Author: lattner

lib/Sema/CodeSynthesis.cpp

@@ -448,18 +448,20 @@ static Expr *buildTupleExpr(ASTContext &ctx, ArrayRef<Expr*> args) {
 
 
 static Expr *buildTupleForwardingRefExpr(ASTContext &ctx,
-                                         ArrayRef<TuplePatternElt> params,
-                                    ArrayRef<TupleTypeElt> formalIndexTypes) {
-  assert(params.size() == formalIndexTypes.size());
-
+                                         ArrayRef<TuplePatternElt> params) {
   SmallVector<Identifier, 4> labels;
   SmallVector<SourceLoc, 4> labelLocs;
   SmallVector<Expr *, 4> args;
 
   for (unsigned i = 0, e = params.size(); i != e; ++i) {
     const Pattern *param = params[i].getPattern();
     args.push_back(param->buildForwardingRefExpr(ctx));
-    labels.push_back(formalIndexTypes[i].getName());
+    // If this parameter pattern has a name, extract it.
+    if (auto *np =dyn_cast<NamedPattern>(param->getSemanticsProvidingPattern()))
+      labels.push_back(np->getBoundName());
+    else
+      labels.push_back(Identifier());
+    
     labelLocs.push_back(SourceLoc());
   }
 
@@ -497,14 +499,7 @@ static Expr *buildSubscriptIndexReference(ASTContext &ctx, FuncDecl *accessor) {
   if (accessorKind == AccessorKind::IsMaterializeForSet)
     params = params.slice(1);
 
-  // Look for formal subscript labels.
-  auto subscript = cast<SubscriptDecl>(accessor->getAccessorStorageDecl());
-  auto indexType = subscript->getIndicesType();
-  if (auto indexTuple = indexType->getAs<TupleType>()) {
-    return buildTupleForwardingRefExpr(ctx, params, indexTuple->getElements());
-  } else {
-    return buildTupleForwardingRefExpr(ctx, params, TupleTypeElt(indexType));
-  }
+  return buildTupleForwardingRefExpr(ctx, params);
 }
 
 enum class SelfAccessKind {

test/SILGen/crashers_silgen.swift

@@ -0,0 +1,17 @@
+// RUN: %target-swift-frontend -emit-silgen -o /dev/null %s
+
+// <rdar://22000564> Crash on Subscript taking a tuple argument list
+class r22000564 {
+  subscript (position: (Int, Int)) -> Int {
+    get { return 32 }
+    set {}
+  }
+  subscript(native native: Int) -> Int {
+    get { return native }
+    set {}
+  }
+  subscript (position position: (Int, Int)) -> Int {
+    get { return 32 }
+    set {}
+  }
+}