swift-demangle: fix a crash for invalid input

When fed with invalid input, the swift-demangle tool crashed.

rdar://148754959

Author: eeckstein

lib/Demangling/NodePrinter.cpp

@@ -1265,6 +1265,8 @@ void NodePrinter::printFunctionSigSpecializationParams(NodePointer Node,
       break;
     case FunctionSigSpecializationParamKind::ConstantPropFunction:
     case FunctionSigSpecializationParamKind::ConstantPropGlobal: {
+      if (Idx + 2 > End)
+        return;
       Printer << "[";
       print(Node->getChild(Idx++), depth + 1);
       Printer << " : ";
@@ -1280,13 +1282,17 @@ void NodePrinter::printFunctionSigSpecializationParams(NodePointer Node,
     }
     case FunctionSigSpecializationParamKind::ConstantPropInteger:
     case FunctionSigSpecializationParamKind::ConstantPropFloat:
+      if (Idx + 2 > End)
+        return;
       Printer << "[";
       print(Node->getChild(Idx++), depth + 1);
       Printer << " : ";
       print(Node->getChild(Idx++), depth + 1);
       Printer << "]";
       break;
     case FunctionSigSpecializationParamKind::ConstantPropString:
+      if (Idx + 3 > End)
+        return;
       Printer << "[";
       print(Node->getChild(Idx++), depth + 1);
       Printer << " : ";
@@ -1297,6 +1303,8 @@ void NodePrinter::printFunctionSigSpecializationParams(NodePointer Node,
       Printer << "]";
       break;
     case FunctionSigSpecializationParamKind::ConstantPropKeyPath:
+      if (Idx + 4 > End)
+        return;
       Printer << "[";
       print(Node->getChild(Idx++), depth + 1);
       Printer << " : ";
@@ -1308,6 +1316,8 @@ void NodePrinter::printFunctionSigSpecializationParams(NodePointer Node,
       Printer << ">]";
       break;
     case FunctionSigSpecializationParamKind::ClosureProp:
+      if (Idx + 2 > End)
+        return;
       Printer << "[";
       print(Node->getChild(Idx++), depth + 1);
       Printer << " : ";

test/Demangle/Inputs/manglings.txt

@@ -420,6 +420,7 @@ $s4test3fooyyS2f_SfYkztYjrXEF ---> test.foo(@differentiable(reverse) (Swift.Floa
 $s4test3fooyyS2f_SfYkntYjrXEF ---> test.foo(@differentiable(reverse) (Swift.Float, __owned @noDerivative Swift.Float) -> Swift.Float) -> ()
 $s4test3fooyyS2f_SfYktYjrXEF ---> test.foo(@differentiable(reverse) (Swift.Float, @noDerivative Swift.Float) -> Swift.Float) -> ()
 $s4test3fooyyS2f_SfYktYaYbYjrXEF ---> test.foo(@differentiable(reverse) @Sendable (Swift.Float, @noDerivative Swift.Float) async -> Swift.Float) -> ()
+$SSSTf4pd44444_pf ---> function signature specialization <Arg[0] = [Constant Propagated Float : 44444], Return = > of Swift.String
 $sScA ---> Swift.Actor
 $sScGySiG ---> Swift.TaskGroup<Swift.Int>
 $s4test10returnsOptyxycSgxyScMYccSglF ---> test.returnsOpt<A>((@Swift.MainActor () -> A)?) -> (() -> A)?