[unittest/Sema] Add a helper method to infer bindings for a given type variable

This mimics what `determineBestBindings` does but without sorting.

Author: xedin

unittests/Sema/SemaFixture.cpp

@@ -22,6 +22,7 @@
 #include "swift/ClangImporter/ClangImporter.h"
 #include "swift/Serialization/SerializedModuleLoader.h"
 #include "swift/Subsystems.h"
+#include "llvm/ADT/DenseMap.h"
 
 using namespace swift;
 using namespace swift::unittest;
@@ -74,3 +75,27 @@ Type SemaTest::getStdlibType(StringRef name) const {
 
   return Type();
 }
+
+ConstraintSystem::PotentialBindings
+SemaTest::inferBindings(ConstraintSystem &cs, TypeVariableType *typeVar) {
+  llvm::SmallDenseMap<TypeVariableType *, ConstraintSystem::PotentialBindings>
+      cache;
+
+  for (auto *typeVar : cs.getTypeVariables()) {
+    if (!typeVar->getImpl().hasRepresentativeOrFixed())
+      cache.insert({typeVar, cs.inferBindingsFor(typeVar, /*finalize=*/false)});
+  }
+
+  for (auto *typeVar : cs.getTypeVariables()) {
+    auto cachedBindings = cache.find(typeVar);
+    if (cachedBindings == cache.end())
+      continue;
+
+    auto &bindings = cachedBindings->getSecond();
+    bindings.finalize(cs, cache);
+  }
+
+  auto result = cache.find(typeVar);
+  assert(result != cache.end());
+  return result->second;
+}

unittests/Sema/SemaFixture.h

@@ -18,13 +18,16 @@
 #include "swift/Basic/LangOptions.h"
 #include "swift/Basic/Platform.h"
 #include "swift/Basic/SourceManager.h"
-#include "llvm/ADT/StringRef.h"
+#include "swift/Sema/ConstraintSystem.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/Path.h"
 #include "gtest/gtest.h"
 #include <string>
 
+using namespace swift::constraints;
+
 namespace swift {
 namespace unittest {
 
@@ -62,6 +65,9 @@ class SemaTest : public SemaTestBase {
 
 protected:
   Type getStdlibType(StringRef name) const;
+
+  static ConstraintSystem::PotentialBindings
+  inferBindings(ConstraintSystem &cs, TypeVariableType *typeVar);
 };
 
 } // end namespace unittest