Add a demangler option to hide a current module.

This is analogous to ASTPrinter's FullyQualifiedTypesIfAmbiguous option.

This part of a series of patches to bring ASTPrinter and Swift Demangler to
feature parity, which is needed by LLDB, which depends on using the strings
produced by either interchangibly.

rdar://problem/63700540

Author: adrian-prantl

include/swift/Demangling/Demangle.h

@@ -59,6 +59,9 @@ struct DemangleOptions {
   bool DisplayDebuggerGeneratedModule = true;
   bool DisplayStdlibModule = true;
   bool DisplayObjCModule = true;
+  /// If this is nonempty, entities in this module name will not be qualified.
+  llvm::StringRef HidingCurrentModule;
+  /// A function to render generic parameter names.
   std::function<std::string(uint64_t, uint64_t)> GenericParameterName =
       genericParameterName;
 

lib/Demangling/NodePrinter.cpp

@@ -248,6 +248,8 @@ class NodePrinter {
         return Options.DisplayStdlibModule;
       if (Context->getText() == swift::MANGLING_MODULE_OBJC)
         return Options.DisplayObjCModule;
+      if (Context->getText() == Options.HidingCurrentModule)
+        return false;
       if (Context->getText().startswith(LLDB_EXPRESSIONS_MODULE_NAME_PREFIX))
         return Options.DisplayDebuggerGeneratedModule;
     }

test/Demangle/demangle-special-options.test

@@ -7,3 +7,6 @@ RUN: swift-demangle -display-objc-module=true sSo6CGRectVD | %FileCheck %s --che
 OBJC-CGRECT: {{ __C.CGRect$}}
 RUN: swift-demangle -display-objc-module=false sSo6CGRectVD | %FileCheck %s --check-prefix=CGRECT
 CGRECT: {{ CGRect$}}
+
+RUN: swift-demangle -hiding-module=foo _TtC3foo3bar | %FileCheck %s --check-prefix=BAR
+BAR: {{ bar$}}

tools/swift-demangle/swift-demangle.cpp

@@ -85,6 +85,11 @@ static llvm::cl::opt<bool> DisplayObjCModule(
     "display-objc-module", llvm::cl::init(true),
     llvm::cl::desc("Qualify types originating from the __ObjC module"),
     llvm::cl::Hidden);
+
+static llvm::cl::opt<std::string> HidingModule(
+    "hiding-module",
+    llvm::cl::desc("Don't qualify types originating from this module"),
+    llvm::cl::Hidden);
 /// \}
 
 
@@ -249,6 +254,7 @@ int main(int argc, char **argv) {
     options = swift::Demangle::DemangleOptions::SimplifiedUIDemangleOptions();
   options.DisplayStdlibModule = DisplayStdlibModule;
   options.DisplayObjCModule = DisplayObjCModule;
+  options.HidingCurrentModule = HidingModule;
 
   if (InputNames.empty()) {
     CompactMode = true;