Remove special handling of the -experimental-lazy-typecheck flag.

For now, the flag will simply be a frontend flag and the build system will pass
it directly using `-Xfrontend` when appropriate.

Resolves rdar://117168788

Author: tshortli

Sources/SwiftDriver/Driver/Driver.swift

@@ -2084,7 +2084,7 @@ extension Driver {
       case .indexFile:
         compilerOutputType = .indexData
 
-      case .parse, .resolveImports, .typecheck, .experimentalLazyTypecheck,
+      case .parse, .resolveImports, .typecheck,
            .dumpParse, .printAst, .dumpTypeRefinementContexts, .dumpScopeMaps,
            .dumpInterfaceHash, .dumpTypeInfo, .verifyDebugInfo:
         compilerOutputType = nil

Sources/SwiftDriver/Jobs/EmitModuleJob.swift

@@ -84,11 +84,6 @@ extension Driver {
 
     commandLine.appendFlags("-frontend", "-emit-module", "-experimental-skip-non-inlinable-function-bodies-without-types")
 
-    if parsedOptions.hasArgument(.experimentalLazyTypecheck) {
-      commandLine.appendFlag("-experimental-lazy-typecheck")
-      commandLine.appendFlag("-experimental-skip-non-exportable-decls")
-    }
-
     // Add the inputs.
     for input in self.inputFiles where input.type.isPartOfSwiftCompilation {
       commandLine.append(.path(input.file))

Sources/SwiftOptions/Options.swift

@@ -439,7 +439,7 @@ extension Option {
   public static let driverExperimentalExplicitModuleBuild: Option = Option("-experimental-explicit-module-build", .flag, alias: Option.driverExplicitModuleBuild, attributes: [.helpHidden], helpText: "Prebuild module dependencies to make them explicit")
   public static let forceWorkaroundBrokenModules: Option = Option("-experimental-force-workaround-broken-modules", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Attempt unsafe recovery for imported modules with broken modularization")
   public static let experimentalHermeticSealAtLink: Option = Option("-experimental-hermetic-seal-at-link", .flag, attributes: [.helpHidden, .frontend], helpText: "Library code can assume that all clients are visible at linktime, and aggressively strip unused code")
-  public static let experimentalLazyTypecheck: Option = Option("-experimental-lazy-typecheck", .flag, attributes: [.helpHidden, .frontend, .noInteractive, .doesNotAffectIncrementalBuild], helpText: "Parse input file(s), then type-check lazily as needed to produce requested outputs", group: .modes)
+  public static let experimentalLazyTypecheck: Option = Option("-experimental-lazy-typecheck", .flag, attributes: [.helpHidden, .frontend, .noInteractive, .doesNotAffectIncrementalBuild], helpText: "Parse input file(s), then type-check lazily as needed to produce requested outputs")
   public static let experimentalOneWayClosureParams: Option = Option("-experimental-one-way-closure-params", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Enable experimental support for one-way closure parameters")
   public static let ExperimentalPerformanceAnnotations: Option = Option("-experimental-performance-annotations", .flag, attributes: [.helpHidden, .frontend], helpText: "Deprecated, has no effect")
   public static let platformCCallingConventionEQ: Option = Option("-experimental-platform-c-calling-convention=", .joined, alias: Option.platformCCallingConvention, attributes: [.helpHidden, .frontend, .noDriver])

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -7261,16 +7261,6 @@ final class SwiftDriverTests: XCTestCase {
       ]))
     }
   }
-
-  func testEmitModuleExperimentalLazyTypecheck() throws {
-    var driver = try Driver(args: [
-      "swiftc", "test.swift", "-module-name", "Test", "-experimental-lazy-typecheck", "-emit-module-interface"
-    ])
-    let jobs = try driver.planBuild().removingAutolinkExtractJobs()
-    let emitModuleJob = try XCTUnwrap(jobs.first(where: {$0.kind == .emitModule}))
-    XCTAssertTrue(emitModuleJob.commandLine.contains(.flag("-experimental-lazy-typecheck")))
-    XCTAssertTrue(emitModuleJob.commandLine.contains(.flag("-experimental-skip-non-exportable-decls")))
-  }
 }
 
 func assertString(