Merge pull request #41399 from rjmccall/suppressible-compatibility-checks

Fix and generalize the printing of suppressible features

Author: rjmccall

include/swift/AST/ASTPrinter.h

@@ -385,10 +385,14 @@ void getInheritedForPrinting(
 
 StringRef getAccessorKindString(AccessorKind value);
 
-bool printCompatibilityFeatureChecksPre(ASTPrinter &printer, Decl *decl);
-void printCompatibilityFeatureChecksPost(
-    ASTPrinter &printer,
-    llvm::function_ref<void()> printElse = []() -> void {});
+/// Call the given function nested appropriately within #if checks
+/// for the compiler features that it uses.  Note that printBody
+/// may be called multiple times if the declaration uses suppressible
+/// features.
+bool printWithCompatibilityFeatureChecks(ASTPrinter &printer,
+                                         PrintOptions &options,
+                                         Decl *decl,
+                                         llvm::function_ref<void()> printBody);
 
 } // namespace swift
 

include/swift/Basic/Feature.h

@@ -26,9 +26,31 @@ enum class Feature {
   #include "swift/Basic/Features.def"
 };
 
+constexpr unsigned numFeatures() {
+  enum Features {
+#define LANGUAGE_FEATURE(FeatureName, SENumber, Description, Option) \
+    FeatureName,
+#include "swift/Basic/Features.def"
+    NumFeatures
+  };
+  return NumFeatures;
+}
+
+/// Determine whether the given feature is suppressible.
+bool isSuppressibleFeature(Feature feature);
+
 /// Determine the in-source name of the given feature.
 llvm::StringRef getFeatureName(Feature feature);
 
+/// Determine whether the first feature is more recent (and thus implies
+/// the existence of) the second feature.  Only meaningful for suppressible
+/// features.
+inline bool featureImpliesFeature(Feature feature, Feature implied) {
+  // Suppressible features are expected to be listed in order of
+  // addition in Features.def.
+  return (unsigned) feature < (unsigned) implied;
+}
+
 }
 
 #endif // SWIFT_BASIC_FEATURES_H

include/swift/Basic/Features.def

@@ -28,12 +28,26 @@
 //     Option: either a reference to a language option in the form
 //       "langOpts.<option name>" or "true" to indicate that it's always
 //       enabled.
+//
+// Suppressible language features can be suppressed when printing
+// an interface without having to suppress the entire declaration they're
+// contained within.  The declaration will be emitted multiple times,
+// each with a subset of the suppressible features.  To avoid combinatoric
+// re-emission, we assume a linear history: later features in this file
+// imply the existence of earlier features.  (This only needs to apply to
+// suppressible features.)
+//
 //===----------------------------------------------------------------------===//
 
 #ifndef LANGUAGE_FEATURE
 #  error define LANGUAGE_FEATURE before including Features.def
 #endif
 
+#ifndef SUPPRESSIBLE_LANGUAGE_FEATURE
+#define SUPPRESSIBLE_LANGUAGE_FEATURE(FeatureName, SENumber, Description, Option) \
+  LANGUAGE_FEATURE(FeatureName, SENumber, Description, Option)
+#endif
+
 LANGUAGE_FEATURE(StaticAssert, 0, "#assert", langOpts.EnableExperimentalStaticAssert)
 LANGUAGE_FEATURE(AsyncAwait, 296, "async/await", true)
 LANGUAGE_FEATURE(EffectfulProp, 310, "Effectful properties", true)
@@ -57,8 +71,9 @@ LANGUAGE_FEATURE(BuiltinCreateAsyncTaskInGroup, 0, "MainActor executor building
 LANGUAGE_FEATURE(BuiltinMove, 0, "Builtin.move()", true)
 LANGUAGE_FEATURE(BuiltinCopy, 0, "Builtin.copy()", true)
 LANGUAGE_FEATURE(BuiltinStackAlloc, 0, "Builtin.stackAlloc", true)
-LANGUAGE_FEATURE(SpecializeAttributeWithAvailability, 0, "@_specialize attribute with availability", true)
+SUPPRESSIBLE_LANGUAGE_FEATURE(SpecializeAttributeWithAvailability, 0, "@_specialize attribute with availability", true)
 LANGUAGE_FEATURE(BuiltinAssumeAlignment, 0, "Builtin.assumeAlignment", true)
-LANGUAGE_FEATURE(UnsafeInheritExecutor, 0, "@_unsafeInheritExecutor", true)
+SUPPRESSIBLE_LANGUAGE_FEATURE(UnsafeInheritExecutor, 0, "@_unsafeInheritExecutor", true)
 
+#undef SUPPRESSIBLE_LANGUAGE_FEATURE
 #undef LANGUAGE_FEATURE