diff --git a/lib/Sema/TypeCheckGeneric.cpp b/lib/Sema/TypeCheckGeneric.cpp
index 0b3ab22a79bd1..07ec072ff3c5f 100644
--- a/lib/Sema/TypeCheckGeneric.cpp
+++ b/lib/Sema/TypeCheckGeneric.cpp
@@ -468,15 +468,11 @@ void TypeChecker::checkReferencedGenericParams(GenericContext *dc) {
 /// Generic types
 ///
 
-/// Form the interface type of an extension from the raw type and the
-/// extension's list of generic parameters.
-static Type formExtensionInterfaceType(
-                         ExtensionDecl *ext, Type type,
-                         const GenericParamList *genericParams,
-                         SmallVectorImpl<Requirement> &sameTypeReqs,
-                         bool &mustInferRequirements) {
+/// Collect additional requirements into \p sameTypeReqs.
+static void collectAdditionalExtensionRequirements(
+    Type type, SmallVectorImpl<Requirement> &sameTypeReqs) {
   if (type->is<ErrorType>())
-    return type;
+    return;
 
   // Find the nominal type declaration and its parent type.
   if (type->is<ProtocolCompositionType>())
@@ -484,7 +480,7 @@ static Type formExtensionInterfaceType(
 
   // A parameterized protocol type is not a nominal. Unwrap it to get
   // the underlying nominal, and record a same-type requirement for
-  // the primary associated type.
+  // the primary associated types.
   if (auto *paramProtoTy = type->getAs<ParameterizedProtocolType>()) {
     auto *protoTy = paramProtoTy->getBaseType();
     type = protoTy;
@@ -497,15 +493,9 @@ static Type formExtensionInterfaceType(
   Type parentType = type->getNominalParent();
   GenericTypeDecl *genericDecl = type->getAnyGeneric();
 
-  // Reconstruct the parent, if there is one.
+  // Visit the parent type, if there is one.
   if (parentType) {
-    // Build the nested extension type.
-    auto parentGenericParams = genericDecl->getGenericParams()
-                                 ? genericParams->getOuterParameters()
-                                 : genericParams;
-    parentType =
-      formExtensionInterfaceType(ext, parentType, parentGenericParams,
-                                 sameTypeReqs, mustInferRequirements);
+    collectAdditionalExtensionRequirements(parentType, sameTypeReqs);
   }
 
   // Find the nominal type.
@@ -516,59 +506,26 @@ static Type formExtensionInterfaceType(
     nominal = type->getNominalOrBoundGenericNominal();
   }
 
-  // Form the result.
-  Type resultType;
-  SmallVector<Type, 2> genericArgs;
-  if (!nominal->isGeneric() || isa<ProtocolDecl>(nominal)) {
-    resultType = NominalType::get(nominal, parentType,
-                                  nominal->getASTContext());
-  } else if (genericParams) {
-    auto currentBoundType = type->getAs<BoundGenericType>();
-
-    // Form the bound generic type with the type parameters provided.
-    unsigned gpIndex = 0;
-    for (auto gp : *genericParams) {
-      SWIFT_DEFER { ++gpIndex; };
-
+  // If we have a bound generic type, add same-type requirements for each of
+  // its generic arguments.
+  if (auto currentBoundType = type->getAs<BoundGenericType>()) {
+    auto *genericParams = currentBoundType->getDecl()->getGenericParams();
+    for (unsigned gpIndex : indices(genericParams->getParams())) {
+      auto *gp = genericParams->getParams()[gpIndex];
       auto gpType = gp->getDeclaredInterfaceType();
-      genericArgs.push_back(gpType);
 
-      if (currentBoundType) {
-        sameTypeReqs.emplace_back(RequirementKind::SameType, gpType,
-                                  currentBoundType->getGenericArgs()[gpIndex]);
-      }
+      sameTypeReqs.emplace_back(RequirementKind::SameType, gpType,
+                                currentBoundType->getGenericArgs()[gpIndex]);
     }
-
-    resultType = BoundGenericType::get(nominal, parentType, genericArgs);
   }
 
-  // If we have a typealias, try to form type sugar.
+  // If we have a passthrough typealias, add the requirements from its
+  // generic signature.
   if (typealias && TypeChecker::isPassThroughTypealias(
                        typealias, typealias->getUnderlyingType(), nominal)) {
-    auto typealiasSig = typealias->getGenericSignature();
-    SubstitutionMap subMap;
-    if (typealiasSig) {
-      subMap = typealiasSig->getIdentitySubstitutionMap();
-
-      mustInferRequirements = true;
-    }
-
-    resultType = TypeAliasType::get(typealias, parentType, subMap, resultType);
+    for (auto req : typealias->getGenericSignature().getRequirements())
+      sameTypeReqs.push_back(req);
   }
-
-
-  return resultType;
-}
-
-/// Retrieve the generic parameter depth of the extended type.
-static unsigned getExtendedTypeGenericDepth(ExtensionDecl *ext) {
-  auto nominal = ext->getSelfNominalTypeDecl();
-  if (!nominal) return static_cast<unsigned>(-1);
-
-  auto sig = nominal->getGenericSignatureOfContext();
-  if (!sig) return static_cast<unsigned>(-1);
-
-  return sig.getGenericParams().back()->getDepth();
 }
 
 GenericSignature
@@ -605,7 +562,7 @@ GenericSignatureRequest::evaluate(Evaluator &evaluator,
   }
 
   bool allowConcreteGenericParams = false;
-  const auto *genericParams = GC->getGenericParams();
+  auto *genericParams = GC->getGenericParams();
   const auto *where = GC->getTrailingWhereClause();
 
   if (genericParams) {
@@ -650,10 +607,12 @@ GenericSignatureRequest::evaluate(Evaluator &evaluator,
     return GC->getParentForLookup()->getGenericSignatureOfContext();
   }
 
-  auto parentSig = GC->getParentForLookup()->getGenericSignatureOfContext();
+  GenericSignature parentSig;
   SmallVector<TypeLoc, 2> inferenceSources;
   SmallVector<Requirement, 2> sameTypeReqs;
   if (auto VD = dyn_cast_or_null<ValueDecl>(GC->getAsDecl())) {
+    parentSig = GC->getParentForLookup()->getGenericSignatureOfContext();
+
     auto func = dyn_cast<AbstractFunctionDecl>(VD);
     auto subscr = dyn_cast<SubscriptDecl>(VD);
 
@@ -708,38 +667,23 @@ GenericSignatureRequest::evaluate(Evaluator &evaluator,
       }
     }
   } else if (auto *ext = dyn_cast<ExtensionDecl>(GC)) {
-    // Form the interface type of the extension so we can use it as an inference
-    // source.
-    //
-    // FIXME: Push this into the "get interface type" request.
-    bool mustInferRequirements = false;
-    Type extInterfaceType =
-      formExtensionInterfaceType(ext, ext->getExtendedType(),
-                                 genericParams, sameTypeReqs,
-                                 mustInferRequirements);
-    
-    auto cannotReuseNominalSignature = [&]() -> bool {
-      const auto finalDepth = genericParams->getParams().back()->getDepth();
-      return mustInferRequirements
-          || !sameTypeReqs.empty()
-          || ext->getTrailingWhereClause()
-          || (getExtendedTypeGenericDepth(ext) != finalDepth);
-    };
+    parentSig = ext->getExtendedNominal()->getGenericSignatureOfContext();
+    genericParams = nullptr;
+
+    collectAdditionalExtensionRequirements(ext->getExtendedType(), sameTypeReqs);
     
-    // Re-use the signature of the type being extended by default.
-    if (!cannotReuseNominalSignature()) {
-      return ext->getSelfNominalTypeDecl()->getGenericSignatureOfContext();
+   // Re-use the signature of the type being extended by default.
+    if (sameTypeReqs.empty() && !ext->getTrailingWhereClause()) {
+      return parentSig;
     }
 
     // Allow parameters to be equated with concrete types.
     allowConcreteGenericParams = true;
-
-    inferenceSources.emplace_back(nullptr, extInterfaceType);
   }
 
   auto request = InferredGenericSignatureRequest{
       parentSig.getPointer(),
-      GC->getGenericParams(), WhereClauseOwner(GC),
+      genericParams, WhereClauseOwner(GC),
       sameTypeReqs, inferenceSources,
       allowConcreteGenericParams};
   auto sig = evaluateOrDefault(ctx.evaluator, request,
diff --git a/test/Generics/conditional_conformances.swift b/test/Generics/conditional_conformances.swift
index 196065c308cc4..dc7fe35f96866 100644
--- a/test/Generics/conditional_conformances.swift
+++ b/test/Generics/conditional_conformances.swift
@@ -49,6 +49,7 @@ struct RedundantSame<T: P1> {}
 // CHECK-LABEL: ExtensionDecl line={{.*}} base=RedundantSame
 // CHECK-NEXT: (normal_conformance type=RedundantSame<T> protocol=P2)
 extension RedundantSame: P2 where T: P1 {}
+// expected-warning@-1 {{redundant conformance constraint 'T' : 'P1'}}
 
 struct RedundantSuper<T: P4> {}
 // CHECK-LABEL: ExtensionDecl line={{.*}} base=RedundantSuper
@@ -334,6 +335,8 @@ struct RedundancyOrderDependenceGood<T: P1, U> {}
 // CHECK-NEXT: (normal_conformance type=RedundancyOrderDependenceGood<T, U> protocol=P2
 // CHECK-NEXT:   same_type: T U)
 extension RedundancyOrderDependenceGood: P2 where U: P1, T == U {}
+// expected-warning@-1 {{redundant conformance constraint 'U' : 'P1'}}
+
 struct RedundancyOrderDependenceBad<T, U: P1> {}
 // CHECK-LABEL: ExtensionDecl line={{.*}} base=RedundancyOrderDependenceBad
 // CHECK-LABEL: ExtensionDecl line={{.*}} base=RedundancyOrderDependenceBad
diff --git a/test/SourceKit/DocSupport/doc_swift_module.swift.response b/test/SourceKit/DocSupport/doc_swift_module.swift.response
index f1fc0a593b5d3..15e86fbbbff16 100644
--- a/test/SourceKit/DocSupport/doc_swift_module.swift.response
+++ b/test/SourceKit/DocSupport/doc_swift_module.swift.response
@@ -1301,7 +1301,7 @@ func shouldPrintAnyAsKeyword(x x: Any)
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "Self",
-    key.usr: "s:4cake4ProtPAASi7ElementRtzrlE4Selfxmfp",
+    key.usr: "s:4cake4ProtP4Selfxmfp",
     key.offset: 1595,
     key.length: 4
   },
@@ -1649,7 +1649,7 @@ func shouldPrintAnyAsKeyword(x x: Any)
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "Wrapped",
-    key.usr: "s:4cake2S3VA2A2P6RzrlE7Wrappedxmfp",
+    key.usr: "s:4cake2S3V7Wrappedxmfp",
     key.offset: 2041,
     key.length: 7
   },
@@ -2557,7 +2557,7 @@ func shouldPrintAnyAsKeyword(x x: Any)
     ],
     key.offset: 1574,
     key.length: 63,
-    key.fully_annotated_decl: "<decl.extension.protocol><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.protocol usr=\"s:4cake4ProtP\">Prot</ref.protocol></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:4cake4ProtPAASi7ElementRtzrlE4Selfxmfp\">Self</ref.generic_type_param>.<ref.associatedtype usr=\"s:4cake4ProtP7ElementQa\">Element</ref.associatedtype> == <ref.struct usr=\"s:Si\">Int</ref.struct></decl.generic_type_requirement></decl.extension.protocol>",
+    key.fully_annotated_decl: "<decl.extension.protocol><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.protocol usr=\"s:4cake4ProtP\">Prot</ref.protocol></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:4cake4ProtP4Selfxmfp\">Self</ref.generic_type_param>.<ref.associatedtype usr=\"s:4cake4ProtP7ElementQa\">Element</ref.associatedtype> == <ref.struct usr=\"s:Si\">Int</ref.struct></decl.generic_type_requirement></decl.extension.protocol>",
     key.extends: {
       key.kind: source.lang.swift.ref.protocol,
       key.name: "Prot",
@@ -2758,6 +2758,11 @@ func shouldPrintAnyAsKeyword(x x: Any)
   },
   {
     key.kind: source.lang.swift.decl.extension.struct,
+    key.generic_params: [
+      {
+        key.name: "Wrapped"
+      }
+    ],
     key.generic_requirements: [
       {
         key.description: "Wrapped : P6"
@@ -2765,7 +2770,7 @@ func shouldPrintAnyAsKeyword(x x: Any)
     ],
     key.offset: 2022,
     key.length: 80,
-    key.fully_annotated_decl: "<syntaxtype.keyword>extension</syntaxtype.keyword> <ref.struct usr=\"s:4cake2S3V\">S3</ref.struct> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:4cake2S3VA2A2P6RzrlE7Wrappedxmfp\">Wrapped</ref.generic_type_param> : <ref.protocol usr=\"s:4cake2P6P\">P6</ref.protocol></decl.generic_type_requirement>",
+    key.fully_annotated_decl: "<syntaxtype.keyword>extension</syntaxtype.keyword> <ref.struct usr=\"s:4cake2S3V\">S3</ref.struct> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:4cake2S3V7Wrappedxmfp\">Wrapped</ref.generic_type_param> : <ref.protocol usr=\"s:4cake2P6P\">P6</ref.protocol></decl.generic_type_requirement>",
     key.extends: {
       key.kind: source.lang.swift.ref.struct,
       key.name: "S3",
diff --git a/test/SourceKit/DocSupport/doc_swift_module1.swift.response b/test/SourceKit/DocSupport/doc_swift_module1.swift.response
index 662df987b140b..1cae78fc9741d 100644
--- a/test/SourceKit/DocSupport/doc_swift_module1.swift.response
+++ b/test/SourceKit/DocSupport/doc_swift_module1.swift.response
@@ -569,7 +569,7 @@ extension Dictionary.Keys where Key : cake1.P1 {
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "Self",
-    key.usr: "s:5cake12P2PA2A2P3RzrlE4Selfxmfp",
+    key.usr: "s:5cake12P2P4Selfxmfp",
     key.offset: 670,
     key.length: 4
   },
@@ -671,7 +671,7 @@ extension Dictionary.Keys where Key : cake1.P1 {
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "Key",
-    key.usr: "s:SD4KeysV5cake1AC2P1RzrlE3Keyxmfp",
+    key.usr: "s:SD3Keyxmfp",
     key.offset: 836,
     key.length: 3
   },
@@ -1038,7 +1038,7 @@ extension Dictionary.Keys where Key : cake1.P1 {
     ],
     key.offset: 651,
     key.length: 64,
-    key.fully_annotated_decl: "<decl.extension.protocol><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.protocol usr=\"s:5cake12P2P\">P2</ref.protocol></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:5cake12P2PA2A2P3RzrlE4Selfxmfp\">Self</ref.generic_type_param> : <ref.protocol usr=\"s:5cake12P3P\">P3</ref.protocol></decl.generic_type_requirement></decl.extension.protocol>",
+    key.fully_annotated_decl: "<decl.extension.protocol><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.protocol usr=\"s:5cake12P2P\">P2</ref.protocol></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:5cake12P2P4Selfxmfp\">Self</ref.generic_type_param> : <ref.protocol usr=\"s:5cake12P3P\">P3</ref.protocol></decl.generic_type_requirement></decl.extension.protocol>",
     key.extends: {
       key.kind: source.lang.swift.ref.protocol,
       key.name: "P2",
@@ -1110,6 +1110,14 @@ extension Dictionary.Keys where Key : cake1.P1 {
   },
   {
     key.kind: source.lang.swift.decl.extension.struct,
+    key.generic_params: [
+      {
+        key.name: "Key"
+      },
+      {
+        key.name: "Value"
+      }
+    ],
     key.generic_requirements: [
       {
         key.description: "Key : Hashable"
@@ -1120,7 +1128,7 @@ extension Dictionary.Keys where Key : cake1.P1 {
     ],
     key.offset: 804,
     key.length: 66,
-    key.fully_annotated_decl: "<decl.extension.struct><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.struct usr=\"s:SD\">Dictionary</ref.struct>.<ref.struct usr=\"s:SD4KeysV\">Keys</ref.struct></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:SD4KeysV5cake1AC2P1RzrlE3Keyxmfp\">Key</ref.generic_type_param> : <ref.protocol usr=\"s:5cake12P1P\">P1</ref.protocol></decl.generic_type_requirement></decl.extension.struct>",
+    key.fully_annotated_decl: "<decl.extension.struct><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.struct usr=\"s:SD\">Dictionary</ref.struct>.<ref.struct usr=\"s:SD4KeysV\">Keys</ref.struct></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:SD3Keyxmfp\">Key</ref.generic_type_param> : <ref.protocol usr=\"s:5cake12P1P\">P1</ref.protocol></decl.generic_type_requirement></decl.extension.struct>",
     key.extends: {
       key.kind: source.lang.swift.ref.struct,
       key.name: "Keys",
diff --git a/test/SourceKit/DocSupport/doc_swift_module_class_extension.swift.response b/test/SourceKit/DocSupport/doc_swift_module_class_extension.swift.response
index 7af1a0c5b29bb..87befec96d775 100644
--- a/test/SourceKit/DocSupport/doc_swift_module_class_extension.swift.response
+++ b/test/SourceKit/DocSupport/doc_swift_module_class_extension.swift.response
@@ -129,7 +129,7 @@ extension P8 where Self.T : module_with_class_extension.E {
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "T",
-    key.usr: "s:27module_with_class_extension1CCA2A1DCRbzlE1Txmfp",
+    key.usr: "s:27module_with_class_extension1CC1Txmfp",
     key.offset: 130,
     key.length: 1
   },
@@ -344,7 +344,7 @@ extension P8 where Self.T : module_with_class_extension.E {
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "Self",
-    key.usr: "s:27module_with_class_extension2P8PA2A1DC1TRczrlE4Selfxmfp",
+    key.usr: "s:27module_with_class_extension2P8P4Selfxmfp",
     key.offset: 480,
     key.length: 4
   },
@@ -397,7 +397,7 @@ extension P8 where Self.T : module_with_class_extension.E {
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "Self",
-    key.usr: "s:27module_with_class_extension2P8PA2A1EC1TRczrlE4Selfxmfp",
+    key.usr: "s:27module_with_class_extension2P8P4Selfxmfp",
     key.offset: 559,
     key.length: 4
   },
@@ -470,6 +470,11 @@ extension P8 where Self.T : module_with_class_extension.E {
   },
   {
     key.kind: source.lang.swift.decl.extension.class,
+    key.generic_params: [
+      {
+        key.name: "T"
+      }
+    ],
     key.generic_requirements: [
       {
         key.description: "T : D"
@@ -477,7 +482,7 @@ extension P8 where Self.T : module_with_class_extension.E {
     ],
     key.offset: 112,
     key.length: 87,
-    key.fully_annotated_decl: "<decl.extension.class><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.class usr=\"s:27module_with_class_extension1CC\">C</ref.class></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:27module_with_class_extension1CCA2A1DCRbzlE1Txmfp\">T</ref.generic_type_param> : <ref.class usr=\"s:27module_with_class_extension1DC\">D</ref.class></decl.generic_type_requirement></decl.extension.class>",
+    key.fully_annotated_decl: "<decl.extension.class><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.class usr=\"s:27module_with_class_extension1CC\">C</ref.class></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:27module_with_class_extension1CC1Txmfp\">T</ref.generic_type_param> : <ref.class usr=\"s:27module_with_class_extension1DC\">D</ref.class></decl.generic_type_requirement></decl.extension.class>",
     key.extends: {
       key.kind: source.lang.swift.ref.class,
       key.name: "C",
@@ -630,7 +635,7 @@ extension P8 where Self.T : module_with_class_extension.E {
     ],
     key.offset: 461,
     key.length: 77,
-    key.fully_annotated_decl: "<decl.extension.protocol><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.protocol usr=\"s:27module_with_class_extension2P8P\">P8</ref.protocol></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:27module_with_class_extension2P8PA2A1DC1TRczrlE4Selfxmfp\">Self</ref.generic_type_param>.<ref.associatedtype usr=\"s:27module_with_class_extension2P8P1TQa\">T</ref.associatedtype> : <ref.class usr=\"s:27module_with_class_extension1DC\">D</ref.class></decl.generic_type_requirement></decl.extension.protocol>",
+    key.fully_annotated_decl: "<decl.extension.protocol><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.protocol usr=\"s:27module_with_class_extension2P8P\">P8</ref.protocol></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:27module_with_class_extension2P8P4Selfxmfp\">Self</ref.generic_type_param>.<ref.associatedtype usr=\"s:27module_with_class_extension2P8P1TQa\">T</ref.associatedtype> : <ref.class usr=\"s:27module_with_class_extension1DC\">D</ref.class></decl.generic_type_requirement></decl.extension.protocol>",
     key.extends: {
       key.kind: source.lang.swift.ref.protocol,
       key.name: "P8",
@@ -656,7 +661,7 @@ extension P8 where Self.T : module_with_class_extension.E {
     ],
     key.offset: 540,
     key.length: 77,
-    key.fully_annotated_decl: "<decl.extension.protocol><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.protocol usr=\"s:27module_with_class_extension2P8P\">P8</ref.protocol></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:27module_with_class_extension2P8PA2A1EC1TRczrlE4Selfxmfp\">Self</ref.generic_type_param>.<ref.associatedtype usr=\"s:27module_with_class_extension2P8P1TQa\">T</ref.associatedtype> : <ref.class usr=\"s:27module_with_class_extension1EC\">E</ref.class></decl.generic_type_requirement></decl.extension.protocol>",
+    key.fully_annotated_decl: "<decl.extension.protocol><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.protocol usr=\"s:27module_with_class_extension2P8P\">P8</ref.protocol></decl.name> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:27module_with_class_extension2P8P4Selfxmfp\">Self</ref.generic_type_param>.<ref.associatedtype usr=\"s:27module_with_class_extension2P8P1TQa\">T</ref.associatedtype> : <ref.class usr=\"s:27module_with_class_extension1EC\">E</ref.class></decl.generic_type_requirement></decl.extension.protocol>",
     key.extends: {
       key.kind: source.lang.swift.ref.protocol,
       key.name: "P8",
diff --git a/test/SourceKit/DocSupport/doc_system_module_underscored.swift.response b/test/SourceKit/DocSupport/doc_system_module_underscored.swift.response
index 69b177d042cbb..f9293f870ddd7 100644
--- a/test/SourceKit/DocSupport/doc_system_module_underscored.swift.response
+++ b/test/SourceKit/DocSupport/doc_system_module_underscored.swift.response
@@ -219,7 +219,7 @@ protocol Other1 {
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "T",
-    key.usr: "s:16UnderscoredProto1AVAASSRszlE1Txmfp",
+    key.usr: "s:16UnderscoredProto1AV1Txmfp",
     key.offset: 227,
     key.length: 1
   },
@@ -849,7 +849,7 @@ protocol Other1 {
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "T",
-    key.usr: "s:16UnderscoredProto1DVAASQRzrlE1Txmfp",
+    key.usr: "s:16UnderscoredProto1DV1Txmfp",
     key.offset: 1411,
     key.length: 1
   },
@@ -911,7 +911,7 @@ protocol Other1 {
   {
     key.kind: source.lang.swift.ref.generic_type_param,
     key.name: "T",
-    key.usr: "s:16UnderscoredProto1DVAASQRzrlE1Txmfp",
+    key.usr: "s:16UnderscoredProto1DV1Txmfp",
     key.offset: 1484,
     key.length: 1
   },
@@ -1050,6 +1050,11 @@ protocol Other1 {
   },
   {
     key.kind: source.lang.swift.decl.extension.struct,
+    key.generic_params: [
+      {
+        key.name: "T"
+      }
+    ],
     key.generic_requirements: [
       {
         key.description: "T == String"
@@ -1057,7 +1062,7 @@ protocol Other1 {
     ],
     key.offset: 209,
     key.length: 185,
-    key.fully_annotated_decl: "<decl.extension.struct><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.struct usr=\"s:16UnderscoredProto1AV\">A</ref.struct></decl.name> : <ref.protocol usr=\"s:16UnderscoredProto01_A6Proto2P\">_UnderscoredProto2</ref.protocol> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:16UnderscoredProto1AVAASSRszlE1Txmfp\">T</ref.generic_type_param> == <ref.struct usr=\"s:SS\">String</ref.struct></decl.generic_type_requirement></decl.extension.struct>",
+    key.fully_annotated_decl: "<decl.extension.struct><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.struct usr=\"s:16UnderscoredProto1AV\">A</ref.struct></decl.name> : <ref.protocol usr=\"s:16UnderscoredProto01_A6Proto2P\">_UnderscoredProto2</ref.protocol> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:16UnderscoredProto1AV1Txmfp\">T</ref.generic_type_param> == <ref.struct usr=\"s:SS\">String</ref.struct></decl.generic_type_requirement></decl.extension.struct>",
     key.conforms: [
       {
         key.kind: source.lang.swift.ref.protocol,
@@ -1520,6 +1525,14 @@ protocol Other1 {
   },
   {
     key.kind: source.lang.swift.decl.extension.struct,
+    key.generic_params: [
+      {
+        key.name: "T"
+      },
+      {
+        key.name: "U"
+      }
+    ],
     key.generic_requirements: [
       {
         key.description: "T : Equatable"
@@ -1527,7 +1540,7 @@ protocol Other1 {
     ],
     key.offset: 1393,
     key.length: 59,
-    key.fully_annotated_decl: "<decl.extension.struct><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.struct usr=\"s:16UnderscoredProto1DV\">D</ref.struct></decl.name> : <ref.protocol usr=\"s:16UnderscoredProto05_SomeB0P\">_SomeProto</ref.protocol> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:16UnderscoredProto1DVAASQRzrlE1Txmfp\">T</ref.generic_type_param> : <ref.protocol usr=\"s:SQ\">Equatable</ref.protocol></decl.generic_type_requirement></decl.extension.struct>",
+    key.fully_annotated_decl: "<decl.extension.struct><syntaxtype.keyword>extension</syntaxtype.keyword> <decl.name><ref.struct usr=\"s:16UnderscoredProto1DV\">D</ref.struct></decl.name> : <ref.protocol usr=\"s:16UnderscoredProto05_SomeB0P\">_SomeProto</ref.protocol> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:16UnderscoredProto1DV1Txmfp\">T</ref.generic_type_param> : <ref.protocol usr=\"s:SQ\">Equatable</ref.protocol></decl.generic_type_requirement></decl.extension.struct>",
     key.conforms: [
       {
         key.kind: source.lang.swift.ref.protocol,
@@ -1560,6 +1573,14 @@ protocol Other1 {
   },
   {
     key.kind: source.lang.swift.decl.extension.struct,
+    key.generic_params: [
+      {
+        key.name: "T"
+      },
+      {
+        key.name: "U"
+      }
+    ],
     key.generic_requirements: [
       {
         key.description: "T : Other1"
@@ -1570,7 +1591,7 @@ protocol Other1 {
     ],
     key.offset: 1454,
     key.length: 135,
-    key.fully_annotated_decl: "<syntaxtype.keyword>extension</syntaxtype.keyword> <ref.struct usr=\"s:16UnderscoredProto1DV\">D</ref.struct> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:16UnderscoredProto1DV1Txmfp\">T</ref.generic_type_param> : <ref.protocol usr=\"s:16UnderscoredProto6Other1P\">Other1</ref.protocol></decl.generic_type_requirement>, <decl.generic_type_requirement><ref.generic_type_param usr=\"s:16UnderscoredProto1DVAASQRzrlE1Txmfp\">T</ref.generic_type_param> : <ref.protocol usr=\"s:SQ\">Equatable</ref.protocol></decl.generic_type_requirement>",
+    key.fully_annotated_decl: "<syntaxtype.keyword>extension</syntaxtype.keyword> <ref.struct usr=\"s:16UnderscoredProto1DV\">D</ref.struct> <syntaxtype.keyword>where</syntaxtype.keyword> <decl.generic_type_requirement><ref.generic_type_param usr=\"s:16UnderscoredProto1DV1Txmfp\">T</ref.generic_type_param> : <ref.protocol usr=\"s:16UnderscoredProto6Other1P\">Other1</ref.protocol></decl.generic_type_requirement>, <decl.generic_type_requirement><ref.generic_type_param usr=\"s:16UnderscoredProto1DV1Txmfp\">T</ref.generic_type_param> : <ref.protocol usr=\"s:SQ\">Equatable</ref.protocol></decl.generic_type_requirement>",
     key.extends: {
       key.kind: source.lang.swift.ref.struct,
       key.name: "D",