[Sema]: Add Codable synthesis for enums with associated values (swiftlang#34855)

* [Sema]: Add Codable synthesis for enums with associated values

* Incorporate review feedback for enum Codable synthesis

* Implement enum specific versions of existing Codable tests

* Encode parameterless enum cases as

* Add test for overloaded case identifiers

* Align code generation with latest proposal revision

* Put enum codable derivation behind flag

* clang-format sources

* Address review feedback and fix tests

* Add diagnostic for conflicting parameter identifiers

* Restructure code after rebase

Author: drexin

include/swift/AST/Decl.h

@@ -6531,7 +6531,7 @@ class EnumElementDecl : public DeclContext, public ValueDecl {
   bool isIndirect() const {
     return getAttrs().hasAttribute<IndirectAttr>();
   }
-  
+
   /// Do not call this!
   /// It exists to let the AST walkers get the raw value without forcing a request.
   LiteralExpr *getRawValueUnchecked() const { return RawValueExpr; }

include/swift/AST/DiagnosticsSema.def

@@ -2917,6 +2917,13 @@ NOTE(decodable_suggest_overriding_init_here,none,
      "did you mean to override 'init(from:)'?", ())
 NOTE(codable_suggest_overriding_init_here,none,
      "did you mean to override 'init(from:)' and 'encode(to:)'?", ())
+NOTE(codable_enum_duplicate_case_name_here,none,
+     "cannot automatically synthesize %0 because %1 has duplicate "
+     "case name %2", (Type, Type, Identifier))
+NOTE(codable_enum_duplicate_parameter_name_here,none,
+     "cannot automatically synthesize %0 for %1 because "
+     "user defined parameter name %2 in %3 conflicts with "
+     "automatically generated parameter name", (Type, Type, Identifier, Identifier))
 
 WARNING(decodable_property_will_not_be_decoded, none,
         "immutable property will not be decoded because it is declared with "

include/swift/AST/KnownIdentifiers.def

@@ -24,6 +24,7 @@
 
 IDENTIFIER(AllCases)
 IDENTIFIER(allCases)
+IDENTIFIER(allKeys)
 IDENTIFIER(alloc)
 IDENTIFIER(allocWithZone)
 IDENTIFIER(allZeros)
@@ -43,16 +44,20 @@ IDENTIFIER(callAsFunction)
 IDENTIFIER(Change)
 IDENTIFIER_WITH_NAME(code_, "_code")
 IDENTIFIER(CodingKeys)
+IDENTIFIER(codingPath)
 IDENTIFIER(combine)
 IDENTIFIER_(Concurrency)
 IDENTIFIER(container)
+IDENTIFIER(Context)
 IDENTIFIER(CoreGraphics)
 IDENTIFIER(CoreMedia)
 IDENTIFIER(CGFloat)
 IDENTIFIER(CoreFoundation)
+IDENTIFIER(count)
 IDENTIFIER(CVarArg)
 IDENTIFIER(Darwin)
 IDENTIFIER(dealloc)
+IDENTIFIER(debugDescription)
 IDENTIFIER(Decodable)
 IDENTIFIER(decode)
 IDENTIFIER(decodeIfPresent)
@@ -82,18 +87,21 @@ IDENTIFIER(fromRaw)
 IDENTIFIER(hash)
 IDENTIFIER(hasher)
 IDENTIFIER(hashValue)
+IDENTIFIER(init)
 IDENTIFIER(initialize)
 IDENTIFIER(initStorage)
 IDENTIFIER(initialValue)
 IDENTIFIER(into)
 IDENTIFIER(intValue)
+IDENTIFIER(invalidValue)
 IDENTIFIER(Key)
 IDENTIFIER(KeyedDecodingContainer)
 IDENTIFIER(KeyedEncodingContainer)
 IDENTIFIER(keyedBy)
 IDENTIFIER(keyPath)
 IDENTIFIER(makeIterator)
 IDENTIFIER(makeAsyncIterator)
+IDENTIFIER(nestedContainer)
 IDENTIFIER(Iterator)
 IDENTIFIER(AsyncIterator)
 IDENTIFIER(load)
@@ -134,6 +142,8 @@ IDENTIFIER(to)
 IDENTIFIER(toRaw)
 IDENTIFIER(Type)
 IDENTIFIER(type)
+IDENTIFIER(typeMismatch)
+IDENTIFIER(underlyingError)
 IDENTIFIER(Value)
 IDENTIFIER(value)
 IDENTIFIER_WITH_NAME(value_, "_value")

include/swift/AST/KnownStdlibTypes.def

@@ -90,6 +90,8 @@ KNOWN_STDLIB_TYPE_DECL(Decoder, ProtocolDecl, 1)
 KNOWN_STDLIB_TYPE_DECL(KeyedEncodingContainer, NominalTypeDecl, 1)
 KNOWN_STDLIB_TYPE_DECL(KeyedDecodingContainer, NominalTypeDecl, 1)
 KNOWN_STDLIB_TYPE_DECL(RangeReplaceableCollection, ProtocolDecl, 1)
+KNOWN_STDLIB_TYPE_DECL(EncodingError, NominalTypeDecl, 0)
+KNOWN_STDLIB_TYPE_DECL(DecodingError, NominalTypeDecl, 0)
 
 KNOWN_STDLIB_TYPE_DECL(Result, NominalTypeDecl, 2)
 

include/swift/Basic/LangOptions.h

@@ -247,6 +247,9 @@ namespace swift {
     /// Enable experimental flow-sensitive concurrent captures.
     bool EnableExperimentalFlowSensitiveConcurrentCaptures = false;
 
+    /// Enable experimental derivation of `Codable` for enums.
+    bool EnableExperimentalEnumCodableDerivation = false;
+
     /// Disable the implicit import of the _Concurrency module.
     bool DisableImplicitConcurrencyModuleImport = false;
 

include/swift/Option/FrontendOptions.td

@@ -222,6 +222,10 @@ def enable_experimental_flow_sensitive_concurrent_captures :
   Flag<["-"], "enable-experimental-flow-sensitive-concurrent-captures">,
   HelpText<"Enable flow-sensitive concurrent captures">;
 
+def enable_experimental_enum_codable_derivation :
+  Flag<["-"], "enable-experimental-enum-codable-derivation">,
+  HelpText<"Enable experimental derivation of Codable for enums">;
+
 def enable_resilience : Flag<["-"], "enable-resilience">,
      HelpText<"Deprecated, use -enable-library-evolution instead">;
 }

lib/Frontend/CompilerInvocation.cpp

@@ -388,6 +388,9 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.EnableExperimentalFlowSensitiveConcurrentCaptures |=
     Args.hasArg(OPT_enable_experimental_flow_sensitive_concurrent_captures);
 
+  Opts.EnableExperimentalEnumCodableDerivation |=
+      Args.hasArg(OPT_enable_experimental_enum_codable_derivation);
+
   Opts.DisableImplicitConcurrencyModuleImport |=
     Args.hasArg(OPT_disable_implicit_concurrency_module_import);