[Demangler] Fix incorrect assertions in OldRemangler and NodePrinter.

There can be, currently, up to eight child nodes for a FunctionType.
OldRemangler seemed to think there could only be three, while NodePrinter
plumped for six.

rdar://82252704

Author: al45tair

lib/Demangling/NodePrinter.cpp

@@ -772,7 +772,7 @@ class NodePrinter {
   }
 
   void printFunctionType(NodePointer LabelList, NodePointer node) {
-    if (node->getNumChildren() < 2 || node->getNumChildren() > 6) {
+    if (node->getNumChildren() < 2) {
       setInvalid();
       return;
     }
@@ -811,9 +811,14 @@ class NodePrinter {
       assert(false && "Unhandled function type in printFunctionType!");
     }
 
+    unsigned argIndex = node->getNumChildren() - 2;
     unsigned startIndex = 0;
     bool isSendable = false, isAsync = false, isThrows = false;
     auto diffKind = MangledDifferentiabilityKind::NonDifferentiable;
+    if (node->getChild(startIndex)->getKind() == Node::Kind::ClangType) {
+      // handled earlier
+      ++startIndex;
+    }
     if (node->getChild(startIndex)->getKind() ==
           Node::Kind::GlobalActorFunctionType) {
       print(node->getChild(startIndex));
@@ -825,10 +830,6 @@ class NodePrinter {
           (MangledDifferentiabilityKind)node->getChild(startIndex)->getIndex();
       ++startIndex;
     }
-    if (node->getChild(startIndex)->getKind() == Node::Kind::ClangType) {
-      // handled earlier
-      ++startIndex;
-    }
     if (node->getChild(startIndex)->getKind() == Node::Kind::ThrowsAnnotation) {
       ++startIndex;
       isThrows = true;
@@ -863,7 +864,7 @@ class NodePrinter {
     if (isSendable)
       Printer << "@Sendable ";
 
-    printFunctionParameters(LabelList, node->getChild(startIndex),
+    printFunctionParameters(LabelList, node->getChild(argIndex),
                             Options.ShowFunctionArgumentTypes);
 
     if (!Options.ShowFunctionArgumentTypes)
@@ -875,7 +876,7 @@ class NodePrinter {
     if (isThrows)
       Printer << " throws";
 
-    print(node->getChild(startIndex + 1));
+    print(node->getChild(argIndex + 1));
   }
 
   void printImplFunctionType(NodePointer fn) {

lib/Demangling/OldRemangler.cpp

@@ -1098,8 +1098,8 @@ void Remangler::mangleEntityType(Node *node, EntityContext &ctx) {
              node->getKind() == Node::Kind::NoEscapeFunctionType)
                 ? 'F'
                 : 'f');
+    assert(node->getNumChildren() >= 2);
     unsigned inputIndex = node->getNumChildren() - 2;
-    assert(inputIndex <= 1);
     for (unsigned i = 0; i <= inputIndex; ++i)
       mangle(node->begin()[i]);
     auto returnType = node->begin()[inputIndex+1];

test/Demangle/rdar-82252704.swift

@@ -0,0 +1,10 @@
+// rdar://82252704 - [SR-15070]: Declaring a class inside a async throws
+//                   function crashes compiler
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -c %s -o %t/test.o
+
+@available(SwiftStdlib 5.5, *)
+func MyFunction() async throws {
+    class MyClass {}
+}