[SE-0206][Sema] Update Hashable synthesizer to support hash(into:)

This removes the default implementation of hash(into:), and replaces it with automatic synthesis built into the compiler. Hashable can now be implemented by defining either hashValue or hash(into:) -- the compiler supplies the missing half automatically, in all cases.

To determine which hash(into:) implementation to generate, the synthesizer resolves hashValue -- if it finds a synthesized definition for it, then the generated hash(into:) body implements hashing from scratch, feeding components into the hasher. Otherwise, the body implements hash(into:) in terms of hashValue.

Author: lorentey

include/swift/AST/ASTContext.h

@@ -471,12 +471,8 @@ class ASTContext {
   /// Retrieve the declaration of Swift.==(Int, Int) -> Bool.
   FuncDecl *getEqualIntDecl() const;
 
-  /// Retrieve the declaration of
-  /// Swift._combineHashValues(Int, Int) -> Int.
-  FuncDecl *getCombineHashValuesDecl() const;
-
-  /// Retrieve the declaration of Swift._mixInt(Int) -> Int.
-  FuncDecl *getMixIntDecl() const;
+  /// Retrieve the declaration of Swift._hashValue<H>(for: H) -> Int.
+  FuncDecl *getHashValueForDecl() const;
 
   /// Retrieve the declaration of Array.append(element:)
   FuncDecl *getArrayAppendElementDecl() const;

include/swift/AST/DiagnosticsSema.def

@@ -2161,6 +2161,8 @@ ERROR(broken_equatable_requirement,none,
       "Equatable protocol is broken: unexpected requirement", ())
 ERROR(broken_hashable_requirement,none,
       "Hashable protocol is broken: unexpected requirement", ())
+ERROR(broken_hashable_no_hasher,none,
+      "Hashable protocol is broken: Hasher type not found", ())
 ERROR(broken_errortype_requirement,none,
       "Error protocol is broken: unexpected requirement", ())
 ERROR(broken_int_hashable_conformance,none,

include/swift/AST/KnownIdentifiers.def

@@ -33,6 +33,7 @@ IDENTIFIER(atIndexedSubscript)
 IDENTIFIER_(bridgeToObjectiveC)
 IDENTIFIER_WITH_NAME(code_, "_code")
 IDENTIFIER(CodingKeys)
+IDENTIFIER(combine)
 IDENTIFIER(container)
 IDENTIFIER(CoreGraphics)
 IDENTIFIER(CoreMedia)
@@ -57,13 +58,17 @@ IDENTIFIER(error)
 IDENTIFIER(errorDomain)
 IDENTIFIER(forKeyedSubscript)
 IDENTIFIER(Foundation)
+IDENTIFIER(for)
 IDENTIFIER(forKey)
 IDENTIFIER(from)
 IDENTIFIER(fromRaw)
+IDENTIFIER(hash)
+IDENTIFIER(hasher)
 IDENTIFIER(hashValue)
 IDENTIFIER(initialize)
 IDENTIFIER(initStorage)
 IDENTIFIER(initialValue)
+IDENTIFIER(into)
 IDENTIFIER(intValue)
 IDENTIFIER(Key)
 IDENTIFIER(KeyedDecodingContainer)

include/swift/AST/KnownStdlibTypes.def

@@ -50,6 +50,7 @@ KNOWN_STDLIB_TYPE_DECL(Sequence, NominalTypeDecl, 1)
 KNOWN_STDLIB_TYPE_DECL(Dictionary, NominalTypeDecl, 2)
 KNOWN_STDLIB_TYPE_DECL(AnyHashable, NominalTypeDecl, 0)
 KNOWN_STDLIB_TYPE_DECL(MutableCollection, ProtocolDecl, 1)
+KNOWN_STDLIB_TYPE_DECL(Hasher, NominalTypeDecl, 0)
 
 KNOWN_STDLIB_TYPE_DECL(AnyKeyPath, NominalTypeDecl, 0)
 KNOWN_STDLIB_TYPE_DECL(PartialKeyPath, NominalTypeDecl, 1)

lib/AST/ASTContext.cpp

@@ -188,12 +188,9 @@ FOR_KNOWN_FOUNDATION_TYPES(CACHE_FOUNDATION_DECL)
   /// func ==(Int, Int) -> Bool
   FuncDecl *EqualIntDecl = nullptr;
 
-  /// func _combineHashValues(Int, Int) -> Int
-  FuncDecl *CombineHashValuesDecl = nullptr;
+  /// func _hashValue<H: Hashable>(for: H) -> Int
+  FuncDecl *HashValueForDecl = nullptr;
 
-  /// func _mixInt(Int) -> Int
-  FuncDecl *MixIntDecl = nullptr;
-  
   /// func append(Element) -> void
   FuncDecl *ArrayAppendElementDecl = nullptr;
 
@@ -989,44 +986,29 @@ FuncDecl *ASTContext::getGetBoolDecl(LazyResolver *resolver) const {
   return decl;
 }
 
-FuncDecl *ASTContext::getCombineHashValuesDecl() const {
-  if (Impl.CombineHashValuesDecl)
-    return Impl.CombineHashValuesDecl;
-
-  auto resolver = getLazyResolver();
-  auto intType = getIntDecl()->getDeclaredType();
-
-  auto callback = [&](Type inputType, Type resultType) {
-    // Look for the signature (Int, Int) -> Int
-    auto tupleType = dyn_cast<TupleType>(inputType.getPointer());
-    assert(tupleType);
-    return tupleType->getNumElements() == 2 &&
-        tupleType->getElementType(0)->isEqual(intType) &&
-        tupleType->getElementType(1)->isEqual(intType) &&
-        resultType->isEqual(intType);
-  };
-
-  auto decl = lookupLibraryIntrinsicFunc(
-      *this, "_combineHashValues", resolver, callback);
-  Impl.CombineHashValuesDecl = decl;
-  return decl;
-}
-
-FuncDecl *ASTContext::getMixIntDecl() const {
-  if (Impl.MixIntDecl)
-    return Impl.MixIntDecl;
+FuncDecl *ASTContext::getHashValueForDecl() const {
+  if (Impl.HashValueForDecl)
+    return Impl.HashValueForDecl;
 
-  auto resolver = getLazyResolver();
-  auto intType = getIntDecl()->getDeclaredType();
-
-  auto callback = [&](Type inputType, Type resultType) {
-    // Look for the signature (Int) -> Int
-    return inputType->isEqual(intType) && resultType->isEqual(intType);
-  };
-
-  auto decl = lookupLibraryIntrinsicFunc(*this, "_mixInt", resolver, callback);
-  Impl.MixIntDecl = decl;
-  return decl;
+  SmallVector<ValueDecl *, 1> results;
+  lookupInSwiftModule("_hashValue", results);
+  for (auto result : results) {
+    auto *fd = dyn_cast<FuncDecl>(result);
+    if (!fd)
+      continue;
+    auto paramLists = fd->getParameterLists();
+    if (paramLists.size() != 1 || paramLists[0]->size() != 1)
+      continue;
+    auto paramDecl = paramLists[0]->get(0);
+    if (paramDecl->getArgumentName() != Id_for)
+      continue;
+    auto genericParams = fd->getGenericParams();
+    if (!genericParams || genericParams->size() != 1)
+      continue;
+    Impl.HashValueForDecl = fd;
+    return fd;
+  }
+  return nullptr;
 }
 
 FuncDecl *ASTContext::getArrayAppendElementDecl() const {