Demangler: Add option to omit closure signatures (#73331)

include/swift/Demangling/Demangle.h

@@ -63,6 +63,7 @@ struct DemangleOptions {
   bool DisplayObjCModule = true;
   bool PrintForTypeName = false;
   bool ShowAsyncResumePartial = true;
+  bool ShowClosureSignature = true;
 
   /// If this is nonempty, entities in this module name will not be qualified.
   llvm::StringRef HidingCurrentModule;

lib/Demangling/NodePrinter.cpp

@@ -1348,6 +1348,23 @@ static bool needSpaceBeforeType(NodePointer Type) {
   }
 }
 
+/// Determine whether to print an entity's type.
+static bool shouldShowEntityType(Node::Kind EntityKind,
+                                 const DemangleOptions &Options) {
+  switch (EntityKind) {
+  case Node::Kind::ExplicitClosure:
+  case Node::Kind::ImplicitClosure:
+    /// The signature of a closure (its `Type` node) can optionally be omitted.
+    /// Unlike functions which can have overloads, the signature of a closure is
+    /// not needed to be uniquely identified. A closure is uniquely identified
+    /// by its index and parent. Omitting the signature improves the readability
+    /// when long type names are in use.
+    return Options.ShowClosureSignature;
+  default:
+    return true;
+  }
+}
+
 NodePointer NodePrinter::print(NodePointer Node, unsigned depth,
                                bool asPrefixContext) {
   if (depth > NodePrinter::MaxDepth) {
@@ -3484,7 +3501,7 @@ NodePointer NodePrinter::printEntity(NodePointer Entity, unsigned depth,
         Printer << " : ";
         printEntityType(Entity, type, genericFunctionTypeList, depth);
       }
-    } else {
+    } else if (shouldShowEntityType(Entity->getKind(), Options)) {
       assert(TypePr == TypePrinting::FunctionStyle);
       if (MultiWordName || needSpaceBeforeType(type))
         Printer << ' ';

test/Demangle/demangle-special-options.test

@@ -16,3 +16,6 @@ LOCAL: ByteBuffer #1 in closure #6
 
 RUN: swift-demangle -display-local-name-contexts=false s1a4mainyyFySRys5UInt8VGXEfU4_10ByteBufferL_aD | %FileCheck %s --check-prefix=NOLOCAL
 NOLOCAL: {{ ByteBuffer$}}
+
+RUN: swift-demangle -show-closure-signature=false s4mainySiXEfU_ySiXEfU_ | %FileCheck %s --check-prefix=CLOSURE
+CLOSURE: closure #1 in closure #1 in main

tools/swift-demangle/swift-demangle.cpp

@@ -94,6 +94,11 @@ static llvm::cl::opt<std::string> HidingModule(
     "hiding-module",
     llvm::cl::desc("Don't qualify types originating from this module"),
     llvm::cl::Hidden);
+
+static llvm::cl::opt<bool>
+    ShowClosureSignature("show-closure-signature", llvm::cl::init(true),
+                         llvm::cl::desc("Show type signature of closures"),
+                         llvm::cl::Hidden);
 /// \}
 
 
@@ -390,6 +395,7 @@ int main(int argc, char **argv) {
   options.DisplayObjCModule = DisplayObjCModule;
   options.HidingCurrentModule = HidingModule;
   options.DisplayLocalNameContexts = DisplayLocalNameContexts;
+  options.ShowClosureSignature = ShowClosureSignature;
 
   if (InputNames.empty()) {
     CompactMode = true;