Address review feedback.

Author: dan-zheng

include/swift/AST/AutoDiff.h

@@ -388,16 +388,14 @@ template<typename T> struct DenseMapInfo;
 template<> struct DenseMapInfo<AutoDiffConfig> {
   static AutoDiffConfig getEmptyKey() {
     auto *ptr = llvm::DenseMapInfo<void *>::getEmptyKey();
-    return {static_cast<IndexSubset *>(ptr),
-            static_cast<IndexSubset *>(ptr),
+    return {static_cast<IndexSubset *>(ptr), static_cast<IndexSubset *>(ptr),
             static_cast<GenericSignature *>(ptr)};
   }
 
   static AutoDiffConfig getTombstoneKey() {
     auto *ptr = llvm::DenseMapInfo<void *>::getTombstoneKey();
-    return {static_cast<IndexSubset *>(ptr),
-        static_cast<IndexSubset *>(ptr),
-        static_cast<GenericSignature *>(ptr)};
+    return {static_cast<IndexSubset *>(ptr), static_cast<IndexSubset *>(ptr),
+            static_cast<GenericSignature *>(ptr)};
   }
 
   static unsigned getHashValue(const AutoDiffConfig &Val) {

include/swift/AST/DiagnosticsParse.def

@@ -689,14 +689,12 @@ ERROR(sil_witness_protocol_conformance_not_found,none,
 // SIL differentiability witnesses
 ERROR(sil_diff_witness_expected_keyword,PointsToFirstBadToken,
       "expected '%0' in differentiability witness", (StringRef))
-ERROR(sil_diff_witness_expected_parameter_list,PointsToFirstBadToken,
-      "expected an comma-separated list of parameter indices, e.g. (0, 1)", ())
-ERROR(sil_diff_witness_expected_rsquare,PointsToFirstBadToken,
-      "expected ']' to end 'differentiable' attribute", ())
+ERROR(sil_diff_witness_expected_index_list,PointsToFirstBadToken,
+      "expected a space-separated list of indices, e.g. '0 1'", ())
 ERROR(sil_diff_witness_expected_parameter_index,PointsToFirstBadToken,
-      "expected the index of a parameter to differentiate w.r.t.", ())
-ERROR(sil_diff_witness_expected_source_index,PointsToFirstBadToken,
-      "expected the index of a result to differentiate from", ())
+      "expected a parameter index to differentiate with respect to.", ())
+ERROR(sil_diff_witness_expected_result_index,PointsToFirstBadToken,
+      "expected a result index to differentiate with respect to", ())
 
 // SIL Coverage Map
 ERROR(sil_coverage_func_not_found, none,

lib/ParseSIL/ParseSIL.cpp

@@ -6869,9 +6869,9 @@ bool SILParserTUState::parseSILDifferentiabilityWitness(Parser &P) {
     // Function that parses an index into `paramIndices`. Returns true on error.
     auto parseParam = [&]() -> bool {
       unsigned index;
-      // TODO: Reject non-ascending parameter index lists.
+      // TODO: Reject non-ascending index lists.
       if (P.parseUnsignedInteger(index, lastLoc,
-              diag::sil_diff_witness_expected_parameter_list))
+              diag::sil_diff_witness_expected_index_list))
         return true;
       paramIndices.push_back(index);
       return false;