Add unittests for the remangler, particularly to cover error handling.

We currently don't have any tests for remangler error handling, because in
asserts builds it asserts. This patch adds a flag that only exists in !NDEBUG
builds to turn off assertions when inside the unit tests.

include/swift/Demangling/Demangler.h

@@ -80,6 +80,10 @@ class NodeFactory {
 #endif
 
 public:
+#ifndef NDEBUG
+  /// Enabled only by the unit tests to test the failure paths.
+  bool disableAssertionsForUnitTest = false;
+#endif
 
   NodeFactory() {
 #ifdef NODE_FACTORY_DEBUGGING

lib/Demangling/DemanglerAssert.h

@@ -22,9 +22,9 @@
 #include "swift/Demangling/Demangle.h"
 #include "swift/Demangling/NamespaceMacros.h"
 
-#if SWIFT_RUNTIME || defined(NDEBUG)
+#if defined(NDEBUG) || defined (SWIFT_RUNTIME)
 
-// In the runtime and non-asserts builds, DEMANGLER_ASSERT() returns an error
+// In the runtime and non-asserts builds, DEMANGLER_ASSERT() returns an error.
 #define DEMANGLER_ASSERT(expr, node)                                           \
   do {                                                                         \
     if (!(expr))                                                               \
@@ -33,14 +33,19 @@
 
 #else
 
-// Except in the runtime, assert builds cause DEMANGLER_ASSERT() to assert()
+// Except in unittests, assert builds cause DEMANGLER_ASSERT() to assert()
 #define DEMANGLER_ASSERT(expr, node)                                           \
   do {                                                                         \
-    if (!(expr))                                                               \
-      swift::Demangle::failAssert(__FILE__, __LINE__, node, #expr);            \
+    if (!(expr)) {                                                             \
+      if (Factory.disableAssertionsForUnitTest)                                \
+        return ManglingError(ManglingError::AssertionFailed, (node),           \
+                             __LINE__);                                        \
+      else                                                                     \
+        swift::Demangle::failAssert(__FILE__, __LINE__, node, #expr);          \
+    }                                                                          \
   } while (0)
 
-#endif // SWIFT_RUNTIME || defined(NDEBUG)
+#endif
 
 // DEMANGLER_ALWAYS_ASSERT() *always* fails the program, even in the runtime
 #define DEMANGLER_ALWAYS_ASSERT(expr, node)                                    \

unittests/CMakeLists.txt

@@ -13,10 +13,12 @@ if(SWIFT_INCLUDE_TOOLS)
   add_subdirectory(Localization)
   add_subdirectory(IDE)
   add_subdirectory(Parse)
+  add_subdirectory(Remangler)
   add_subdirectory(Sema)
   add_subdirectory(SIL)
   add_subdirectory(SwiftDemangle)
   add_subdirectory(Syntax)
+
   if(SWIFT_BUILD_SYNTAXPARSERLIB)
     add_subdirectory(SyntaxParser)
   endif()

unittests/Remangler/CMakeLists.txt

@@ -0,0 +1,10 @@
+add_swift_unittest(SwiftRemangleTests
+  RemangleTest.cpp
+  )
+
+target_link_libraries(SwiftRemangleTests
+  PRIVATE
+  swiftBasic
+  swiftDemangling
+  LLVMTestingSupport
+  )

unittests/Remangler/RemangleTest.cpp

@@ -0,0 +1,127 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/Demangling/Demangle.h"
+#include "swift/Demangling/Demangler.h"
+#include "swift/Strings.h"
+#include "llvm/ADT/StringRef.h"
+
+#include "gtest/gtest.h"
+
+/// Helper class to conveniently construct demangle tree hierarchies.
+class NodeBuilder {
+  using NodePointer = swift::Demangle::NodePointer;
+  using Kind = swift::Demangle::Node::Kind;
+  
+  swift::Demangle::Demangler &m_dem;
+
+public:
+  NodeBuilder(swift::Demangle::Demangler &dem) : m_dem(dem) {
+#ifndef NDEBUG
+    m_dem.disableAssertionsForUnitTest = true;
+#endif
+  }
+  NodePointer Node(Kind kind, StringRef text) {
+    return m_dem.createNode(kind, text);
+  }
+  NodePointer NodeWithIndex(Kind kind, swift::Demangle::Node::IndexType index) {
+    return m_dem.createNode(kind, index);
+  }
+  NodePointer Node(Kind kind, NodePointer child0 = nullptr,
+                   NodePointer child1 = nullptr,
+                   NodePointer child2 = nullptr,
+                   NodePointer child3 = nullptr) {
+    NodePointer node = m_dem.createNode(kind);
+
+    if (child0)
+      node->addChild(child0, m_dem);
+    if (child1)
+      node->addChild(child1, m_dem);
+    if (child2)
+      node->addChild(child2, m_dem);
+    if (child3)
+      node->addChild(child3, m_dem);
+    return node;
+  }
+  NodePointer IntType() {
+    return Node(Node::Kind::Type,
+                Node(Node::Kind::Structure,
+                     Node(Node::Kind::Module, swift::STDLIB_NAME),
+                     Node(Node::Kind::Identifier, "Int")));
+  }
+  NodePointer GlobalTypeMangling(NodePointer type) {
+    assert(type && type->getKind() == Node::Kind::Type);
+    return Node(Node::Kind::Global, Node(Node::Kind::TypeMangling, type));
+  }
+  NodePointer GlobalType(NodePointer type) {
+    assert(type && type->getKind() != Node::Kind::Type &&
+           type->getKind() != Node::Kind::TypeMangling &&
+           type->getKind() != Node::Kind::Global);
+    return GlobalTypeMangling(Node(Node::Kind::Type, type));
+  }
+
+  ManglingErrorOr<StringRef> remangle(NodePointer node) {
+    return mangleNode(
+        node,
+        [](SymbolicReferenceKind, const void *) -> NodePointer {
+          return nullptr;
+        },
+        m_dem);
+  }
+  std::string remangleResult(NodePointer node) {
+    return remangle(node).result().str();
+  }
+  bool remangleSuccess(NodePointer node) {
+    return remangle(node).isSuccess();
+  }
+};
+
+TEST(TestSwiftRemangler, DependentGenericConformanceRequirement) {
+  using namespace swift::Demangle;
+  using Kind = swift::Demangle::Node::Kind;
+  Demangler dem;
+  NodeBuilder b(dem);
+  {
+    // Well-formed.
+    NodePointer n = b.GlobalType(b.Node(
+        Kind::DependentGenericType,
+        b.Node(Kind::DependentGenericType,
+               b.Node(Kind::DependentGenericSignature,
+                      b.NodeWithIndex(Kind::DependentGenericParamCount, 1),
+                      b.Node(Kind::DependentGenericConformanceRequirement,
+                             b.Node(Kind::Type,
+                                    b.Node(Kind::DependentGenericParamType,
+                                           b.NodeWithIndex(Kind::Index, 0),
+                                           b.NodeWithIndex(Kind::Index, 0))),
+                             b.Node(Kind::Type,
+                                    b.Node(Kind::Protocol,
+                                           b.Node(Kind::Module, "M"),
+                                           b.Node(Kind::Identifier, "B"))))),
+               b.IntType())));
+    ASSERT_EQ(b.remangleResult(n), "$sSi1M1BRzluuD");
+  }
+  {
+    // Malformed.
+    NodePointer n = b.GlobalType(b.Node(
+        Kind::DependentGenericType,
+        b.Node(Kind::DependentGenericType,
+               b.Node(Kind::DependentGenericSignature,
+                      b.NodeWithIndex(Kind::DependentGenericParamCount, 1),
+                      b.Node(Kind::DependentGenericConformanceRequirement,
+                             b.Node(Kind::Type,
+                                    b.Node(Kind::DependentGenericParamType,
+                                           b.NodeWithIndex(Kind::Index, 0),
+                                           b.NodeWithIndex(Kind::Index, 0))))),
+               b.IntType())));
+    ASSERT_FALSE(b.remangleSuccess(n));
+  }
+}