Frontend: Add -experimental-skip-non-inlinable-function-bodies-is-lazy.

This option causes the -experimental-lazy-typecheck and
-experimental-skip-non-exportable-decls options to be inferred from the
presense of -experimental-skip-non-inlinable-function-bodies. This new option
is meant to be a temporary testing aid that allows lazy typechecking to be
tested on projects without full build system support for passing the other
flags to the right jobs.

Resolves rdar://118938251

Author: tshortli

Diff for: include/swift/Option/FrontendOptions.td

@@ -1130,6 +1130,11 @@ def experimental_skip_all_function_bodies:
   Flag<["-"], "experimental-skip-all-function-bodies">,
   HelpText<"Skip type-checking function bodies and all SIL generation">;
 
+def experimental_skip_non_inlinable_function_bodies_is_lazy
+  : Flag<["-"], "experimental-skip-non-inlinable-function-bodies-is-lazy">,
+  HelpText<"Infer lazy typechecking for "
+           "-experimental-skip-non-inlinable-function-bodies">;
+
 def experimental_allow_module_with_compiler_errors:
   Flag<["-"], "experimental-allow-module-with-compiler-errors">,
   Flags<[HelpHidden]>,

Diff for: lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -322,6 +322,10 @@ bool ArgsToFrontendOptionsConverter::convert(
 
   Opts.SkipNonExportableDecls |=
       Args.hasArg(OPT_experimental_skip_non_exportable_decls);
+  Opts.SkipNonExportableDecls |=
+      Args.hasArg(OPT_experimental_skip_non_inlinable_function_bodies) &&
+      Args.hasArg(OPT_experimental_skip_non_inlinable_function_bodies_is_lazy);
+
   Opts.DebugPrefixSerializedDebuggingOptions |=
       Args.hasArg(OPT_prefix_serialized_debugging_options);
   Opts.EnableSourceImport |= Args.hasArg(OPT_enable_source_import);

Diff for: lib/Frontend/CompilerInvocation.cpp

@@ -1503,6 +1503,9 @@ static bool ParseTypeCheckerArgs(TypeCheckerOptions &Opts, ArgList &Args,
   Opts.DebugGenericSignatures |= Args.hasArg(OPT_debug_generic_signatures);
 
   Opts.EnableLazyTypecheck |= Args.hasArg(OPT_experimental_lazy_typecheck);
+  Opts.EnableLazyTypecheck |=
+      Args.hasArg(OPT_experimental_skip_non_inlinable_function_bodies) &&
+      Args.hasArg(OPT_experimental_skip_non_inlinable_function_bodies_is_lazy);
 
   return HadError;
 }

Diff for: test/Serialization/lazy-typecheck.swift

@@ -15,3 +15,8 @@
 //     and -experimental-skip-non-exportable-decls can be used by the same client as in (1).
 // RUN: %target-swift-frontend -swift-version 5 %S/../Inputs/lazy_typecheck.swift -module-name lazy_typecheck -enable-library-evolution -parse-as-library -package-name Package -DFLAG -emit-module -emit-module-path %t/lazy-skip-non-inlinable/lazy_typecheck.swiftmodule -debug-forbid-typecheck-prefix NoTypecheck -experimental-lazy-typecheck -experimental-skip-non-inlinable-function-bodies -experimental-skip-non-exportable-decls
 // RUN: %target-swift-frontend -package-name Package -typecheck -verify %S/../Inputs/lazy_typecheck_client.swift -DFLAG -I %t/lazy-skip-non-inlinable
+
+// (4) Verify that a module built with -experimental-skip-non-inlinable-function-bodies-is-lazy implies
+//     -experimental-lazy-typecheck and -experimental-skip-non-exportable-decls.
+// RUN: %target-swift-frontend -swift-version 5 %S/../Inputs/lazy_typecheck.swift -module-name lazy_typecheck -enable-library-evolution -parse-as-library -package-name Package -DFLAG -emit-module -emit-module-path %t/lazy-skip-non-inlinable-is-lazy/lazy_typecheck.swiftmodule -debug-forbid-typecheck-prefix NoTypecheck -experimental-skip-non-inlinable-function-bodies -experimental-skip-non-inlinable-function-bodies-is-lazy
+// RUN: %target-swift-frontend -package-name Package -typecheck -verify %S/../Inputs/lazy_typecheck_client.swift -DFLAG -I %t/lazy-skip-non-inlinable-is-lazy