[Compile Time Constant Extraction] Extract Nil Values for Optionals

Author: Venkatesh Sriram

include/swift/AST/ConstTypeInfo.h

@@ -43,6 +43,7 @@ class CompileTimeValue {
     StaticFunctionCall,
     MemberReference,
     InterpolatedString,
+    NilLiteral,
     Runtime
   };
 
@@ -72,6 +73,22 @@ class RawLiteralValue : public CompileTimeValue {
   std::string Value;
 };
 
+/// A representation of an Optional<Wrapped> value declared as nil
+/// or left undeclared.
+///
+/// Nil values were previously represented as RawLiteralValue with
+/// value "nil". This caused ambiguous values when extracting values,
+/// such as an Optional<String> of value "nil".
+
+class NilLiteralValue : public CompileTimeValue {
+public:
+  NilLiteralValue() : CompileTimeValue(ValueKind::NilLiteral) {}
+
+  static bool classof(const CompileTimeValue *T) {
+    return T->getKind() == ValueKind::NilLiteral;
+  }
+};
+
 struct FunctionParameter {
   std::string Label;
   swift::Type Type;

lib/ConstExtract/ConstExtract.cpp

@@ -198,8 +198,7 @@ static std::optional<std::string> extractRawLiteral(Expr *expr) {
     switch (expr->getKind()) {
     case ExprKind::BooleanLiteral:
     case ExprKind::FloatLiteral:
-    case ExprKind::IntegerLiteral:
-    case ExprKind::NilLiteral: {
+    case ExprKind::IntegerLiteral: {
       std::string literalOutput;
       llvm::raw_string_ostream OutputStream(literalOutput);
       expr->printConstExprValue(&OutputStream, nullptr);
@@ -230,7 +229,6 @@ static std::shared_ptr<CompileTimeValue> extractCompileTimeValue(Expr *expr) {
     case ExprKind::BooleanLiteral:
     case ExprKind::FloatLiteral:
     case ExprKind::IntegerLiteral:
-    case ExprKind::NilLiteral:
     case ExprKind::StringLiteral: {
       auto rawLiteral = extractRawLiteral(expr);
       if (rawLiteral.has_value()) {
@@ -240,6 +238,10 @@ static std::shared_ptr<CompileTimeValue> extractCompileTimeValue(Expr *expr) {
       break;
     }
 
+    case ExprKind::NilLiteral: {
+      return std::make_shared<NilLiteralValue>();
+    }
+
     case ExprKind::Array: {
       auto arrayExpr = cast<ArrayExpr>(expr);
       std::vector<std::shared_ptr<CompileTimeValue>> elementValues;
@@ -710,6 +712,11 @@ void writeValue(llvm::json::OStream &JSON,
     break;
   }
 
+  case CompileTimeValue::ValueKind::NilLiteral: {
+    JSON.attribute("valueKind", "NilLiteral");
+    break;
+  }
+
   case CompileTimeValue::ValueKind::InitCall: {
     auto initCallValue = cast<InitCallValue>(value);
 

test/ConstExtraction/ExtractFromObjcImplementationExtension.swift

@@ -24,7 +24,7 @@ extension ImplClass: MyProto {
 
 // CHECK:   "label": "defaultNilProperty",
 // CHECK:   "type": "Swift.Optional<AnyObject>",
-// CHECK:   "value": "nil"
+// CHECK:   "valueKind": "NilLiteral"
 
 // CHECK:   "label": "notStoredProperty",
 // CHECK:   "type": "Swift.Bool",

test/ConstExtraction/ExtractLiterals.swift

@@ -94,6 +94,12 @@ public struct PropertyWrappers : MyProto {
      var projectedValue: (V, V?) { (self.value, self.lastValue) }
 }
 
+public struct Optionals: MyProto {
+    let int1: Bool? = nil
+    let string1: String?
+    static var float1: Float?
+}
+
 // CHECK: [
 // CHECK-NEXT:  {
 // CHECK-NEXT:    "typeName": "ExtractLiterals.Bools",
@@ -131,8 +137,7 @@ public struct PropertyWrappers : MyProto {
 // CHECK-NEXT:        "isComputed": "false",
 // CHECK-NEXT:        "file": "{{.*}}test{{/|\\\\}}ConstExtraction{{/|\\\\}}ExtractLiterals.swift",
 // CHECK-NEXT:        "line": 11,
-// CHECK-NEXT:        "valueKind": "RawLiteral",
-// CHECK-NEXT:        "value": "nil"
+// CHECK-NEXT:        "valueKind": "NilLiteral"
 // CHECK-NEXT:      }
 // CHECK-NEXT:    ]
 // CHECK-NEXT:  },
@@ -617,5 +622,54 @@ public struct PropertyWrappers : MyProto {
 // CHECK-NEXT:        "valueKind": "Runtime"
 // CHECK-NEXT:      } 
 // CHECK-NEXT:    ]
+// CHECK-NEXT:  },
+// CHECK-NEXT:  {
+// CHECK-NEXT:    "typeName": "ExtractLiterals.Optionals",
+// CHECK-NEXT:    "mangledTypeName": "15ExtractLiterals9OptionalsV",
+// CHECK-NEXT:    "kind": "struct",
+// CHECK-NEXT:    "file": "{{.*}}test{{/|\\\\}}ConstExtraction{{/|\\\\}}ExtractLiterals.swift",
+// CHECK-NEXT:    "line": 97,
+// CHECK-NEXT:    "conformances": [
+// CHECK-NEXT:      "ExtractLiterals.MyProto"
+// CHECK-NEXT:    ],
+// CHECK-NEXT:    "allConformances": [
+// CHECK-NEXT:      {
+// CHECK-NEXT:        "protocolName": "ExtractLiterals.MyProto",
+// CHECK-NEXT:        "conformanceDefiningModule": "ExtractLiterals"
+// CHECK-NEXT:      }
+// CHECK-NEXT:    ],
+// CHECK-NEXT:    "associatedTypeAliases": [],
+// CHECK-NEXT:    "properties": [
+// CHECK-NEXT:      {
+// CHECK-NEXT:        "label": "int1",
+// CHECK-NEXT:        "type": "Swift.Optional<Swift.Bool>",
+// CHECK-NEXT:        "mangledTypeName": "n/a - deprecated",
+// CHECK-NEXT:        "isStatic": "false",
+// CHECK-NEXT:        "isComputed": "false",
+// CHECK-NEXT:        "file": "{{.*}}test{{/|\\\\}}ConstExtraction{{/|\\\\}}ExtractLiterals.swift",
+// CHECK-NEXT:        "line": 98,
+// CHECK-NEXT:        "valueKind": "NilLiteral"
+// CHECK-NEXT:      },
+// CHECK-NEXT:      {
+// CHECK-NEXT:        "label": "string1",
+// CHECK-NEXT:        "type": "Swift.Optional<Swift.String>",
+// CHECK-NEXT:        "mangledTypeName": "n/a - deprecated",
+// CHECK-NEXT:        "isStatic": "false",
+// CHECK-NEXT:        "isComputed": "false",
+// CHECK-NEXT:        "file": "{{.*}}test{{/|\\\\}}ConstExtraction{{/|\\\\}}ExtractLiterals.swift",
+// CHECK-NEXT:        "line": 99,
+// CHECK-NEXT:        "valueKind": "Runtime"
+// CHECK-NEXT:      },
+// CHECK-NEXT:      {
+// CHECK-NEXT:        "label": "float1",
+// CHECK-NEXT:        "type": "Swift.Optional<Swift.Float>",
+// CHECK-NEXT:        "mangledTypeName": "n/a - deprecated",
+// CHECK-NEXT:        "isStatic": "true",
+// CHECK-NEXT:        "isComputed": "false",
+// CHECK-NEXT:        "file": "{{.*}}test{{/|\\\\}}ConstExtraction{{/|\\\\}}ExtractLiterals.swift",
+// CHECK-NEXT:       "line": 100,
+// CHECK-NEXT:        "valueKind": "NilLiteral"
+// CHECK-NEXT:      }
+// CHECK-NEXT:    ]
 // CHECK-NEXT:  }
 // CHECK-NEXT:]