Add the set of diagnostic categories to each migratable feature

The name of a migratable feature might differ from the names of the
diagnostic groups containing the diagnostics that are used to drive
migration for that feature. Provide the set of diagnostic categories
that are associated with each migratable feature as part of the
supported features list.

Author: DougGregor

lib/Basic/SupportedFeatures.cpp

@@ -13,6 +13,7 @@
 #include <array>
 #include <vector>
 
+#include "swift/AST/DiagnosticGroups.h"
 #include "swift/Basic/Feature.h"
 #include "swift/Frontend/Frontend.h"
 
@@ -22,6 +23,32 @@ using namespace swift;
 
 namespace swift {
 namespace features {
+
+/// The subset of diagnostic groups (called categories by the diagnostic machinery) whose diagnostics should be
+/// considered to be part of the migration for this feature.
+///
+///  When making a
+static std::vector<DiagGroupID> migratableCategories(Feature feature) {
+  switch (feature) {
+    case Feature::InnerKind::ExistentialAny:
+      return { DiagGroupID::ExistentialAny };
+    case Feature::InnerKind::InferIsolatedConformances:
+      return { DiagGroupID::IsolatedConformances };
+    case Feature::InnerKind::NonisolatedNonsendingByDefault:
+      return { DiagGroupID::NonisolatedNonsendingByDefault };
+    case Feature::InnerKind::StrictMemorySafety:
+      return { DiagGroupID::StrictMemorySafety };
+
+    // Provide unreachable cases for all of the non-migratable features.
+#define LANGUAGE_FEATURE(FeatureName, SENumber, Description) case Feature::FeatureName:
+#define MIGRATABLE_UPCOMING_FEATURE(FeatureName, SENumber, Version)
+#define MIGRATABLE_EXPERIMENTAL_FEATURE(FeatureName, AvailableInProd)
+#define MIGRATABLE_OPTIONAL_LANGUAGE_FEATURE(FeatureName, SENumber, Name)
+#include "swift/Basic/Features.def"
+    llvm_unreachable("Not a migratable feature");
+  }
+}
+
 /// Print information about what features upcoming/experimental are
 /// supported by the compiler.
 /// The information includes whether a feature is adoptable and for
@@ -50,6 +77,15 @@ void printSupportedFeatures(llvm::raw_ostream &out) {
     out << "{ \"name\": \"" << feature.getName() << "\"";
     if (feature.isMigratable()) {
       out << ", \"migratable\": true";
+
+      auto categories = migratableCategories(feature);
+      out << ", \"categories\": [";
+      llvm::interleave(categories, [&out](DiagGroupID diagGroupID) {
+        out << "\"" << getDiagGroupInfoByID(diagGroupID).name << "\"";
+      }, [&out] {
+        out << ", ";
+      });
+      out << "]";
     }
     if (auto version = feature.getLanguageVersion()) {
       out << ", \"enabled_in\": \"" << *version << "\"";

test/Frontend/print-supported-features.swift

@@ -2,9 +2,9 @@
 
 // CHECK: "features": {
 // CHECK-NEXT:   "upcoming": [
-// CHECK:     { "name": "{{.*}}"{{, "migratable": true}}, "enabled_in": "{{.*}}" }
+// CHECK:     { "name": "InferIsolatedConformances", "migratable": true, "categories": ["IsolatedConformances"], "enabled_in": "7" },
 // CHECK:   ],
-// CHECK-NEXT:   "experimental": [
+// CHECK:   "experimental": [
 // CHECK:     { "name": "{{.*}}" }
 // CHECK:   ]
 // CHECK: }