[PrintAsClang] Tweak fallback member sort rules

Compare the names of all extension members first, before attempting weirder and more expensive comparisons like stringified type and mangled name. This gives us a sort order that’s a little more comprehensible to humans.

Author: beccadax

lib/PrintAsClang/ModuleContentsWriter.cpp

@@ -117,8 +117,6 @@ class ReferencedTypeFinder : public TypeDeclFinder {
   }
 };
 
-namespace {
-
 namespace compare_detail {
 
 enum : int {
@@ -244,7 +242,7 @@ static int lastDitchSort(Decl *lhs, Decl *rhs, bool suppressDiagnostic) {
   return result;
 }
 
-}
+} // end namespace compare_detail
 
 /// Comparator for use with \c llvm::array_pod_sort() . This sorts decls into
 /// reverse order since they will be pushed onto a stack.
@@ -334,6 +332,7 @@ static int reverseCompareDecls(Decl * const *lhs, Decl * const *rhs) {
 
   // Still nothing? Fine, we'll look for a difference between the members.
   {
+    // First pass: compare names
     for (auto pair : llvm::zip_equal(lhsMembers, rhsMembers)) {
       auto *lhsMember = dyn_cast<ValueDecl>(std::get<0>(pair)),
            *rhsMember = dyn_cast<ValueDecl>(std::get<1>(pair));
@@ -345,9 +344,19 @@ static int reverseCompareDecls(Decl * const *lhs, Decl * const *rhs) {
       ASSERT(lhsMember && rhsMember);
 
       COMPARE(getNameString(lhsMember), getNameString(rhsMember));
+    }
+
+    // Second pass: compare other traits.
+    for (auto pair : llvm::zip_equal(lhsMembers, rhsMembers)) {
+      auto *lhsMember = dyn_cast<ValueDecl>(std::get<0>(pair)),
+           *rhsMember = dyn_cast<ValueDecl>(std::get<1>(pair));
+      if (!lhsMember || !rhsMember)
+        continue;
+
       COMPARE(getTypeString(lhsMember), getTypeString(rhsMember));
       COMPARE(getGenericSignatureString(lhsMember),
               getGenericSignatureString(rhsMember));
+      COMPARE(getMangledNameString(lhsMember), getMangledNameString(rhsMember));
     }
   }
 
@@ -361,7 +370,6 @@ static int reverseCompareDecls(Decl * const *lhs, Decl * const *rhs) {
 
 #undef COMPARE
 }
-}
 
 class ModuleWriter {
   enum class EmissionState { NotYetDefined = 0, DefinitionRequested, Defined };

test/PrintAsObjC/extensions.swift

@@ -96,22 +96,22 @@ extension A5 {
 // CHECK-NEXT: @interface A6
 @objc class A6 {}
 
-extension A6 {
-  @objc(skippedInt:) func skipped(_: Int) {}
-  @objc func abc() {}
-}
 extension A6 {
   @objc(skippedBool:) func skipped(_: Bool) {}
   @objc func def() {}
 }
+extension A6 {
+  @objc(skippedInt:) func skipped(_: Int) {}
+  @objc func abc() {}
+}
 // CHECK: @interface A6 (SWIFT_EXTENSION(extensions))
-// CHECK-NEXT: - (void)skippedBool:
-// CHECK-NEXT: - (void)def
+// CHECK-NEXT: - (void)skippedInt:
+// CHECK-NEXT: - (void)abc
 // CHECK-NEXT: @end
 // CHECK-EMPTY:
 // CHECK-NEXT: @interface A6 (SWIFT_EXTENSION(extensions))
-// CHECK-NEXT: - (void)skippedInt:
-// CHECK-NEXT: - (void)abc
+// CHECK-NEXT: - (void)skippedBool:
+// CHECK-NEXT: - (void)def
 // CHECK-NEXT: @end
 // CHECK-EMPTY: