Parse @_semantics

Author: CodaFi

Sources/SwiftParser/Attributes.swift

@@ -55,6 +55,8 @@ extension Parser {
       return RawSyntax(self.parseSPIAttribute())
     case ._implements:
       return RawSyntax(self.parseImplementsAttribute())
+    case ._semantics:
+      return RawSyntax(self.parseSemanticsAttribute())
     default:
       break
     }
@@ -737,6 +739,28 @@ extension Parser {
   }
 }
 
+extension Parser {
+  mutating func parseSemanticsAttribute() -> RawAttributeSyntax {
+    let (unexpectedBeforeAtSign, atSign) = self.expect(.atSign)
+    let (unexpectedBeforeSemanticsToken, semanticsToken) = self.expectContextualKeyword("_semantics")
+    let (unexpectedBeforeLeftParen, leftParen) = self.expect(.leftParen)
+    let label = self.parseStringLiteral()
+    let (unexpectedBeforeRightParen, rightParen) = self.expect(.rightParen)
+    return RawAttributeSyntax(
+      unexpectedBeforeAtSign,
+      atSignToken: atSign,
+      unexpectedBeforeSemanticsToken,
+      attributeName: semanticsToken,
+      unexpectedBeforeLeftParen,
+      leftParen: leftParen,
+      argument: RawSyntax(label),
+      unexpectedBeforeRightParen,
+      rightParen: rightParen,
+      tokenList: nil,
+      arena: self.arena)
+  }
+}
+
 // MARK: Lookahead
 
 extension Parser.Lookahead {

Tests/SwiftParserTest/Attributes.swift

@@ -192,4 +192,19 @@ final class AttributeTests: XCTestCase {
       }
       """)
   }
+
+  func testSemanticsAttribute() throws {
+    AssertParse(
+      """
+      @_semantics("constant_evaluable")
+      func testRecursion(_ a: Int) -> Int {
+        return a <= 0 ? 0 : testRecursion(a-1)
+      }
+
+      @_semantics("test_driver")
+      internal func interpretRecursion() -> Int {
+        return testRecursion(10)
+      }
+      """)
+  }
 }