Sourcekit/DocSupport: avoid substituting generic types when printing where clauses. rdar://43820510

This makes the printed requirements agree with separately reported generic parameters and requirement.

Author: nkcsgexi

lib/AST/ASTPrinter.cpp

@@ -1391,13 +1391,10 @@ void PrintAST::printSingleDepthOfGenericSignature(
         }
       } else {
         Printer.callPrintStructurePre(PrintStructureKind::GenericRequirement);
-        if (second) {
-          Requirement substReq(req.getKind(), first, second);
-          printRequirement(substReq);
-        } else {
-          Requirement substReq(req.getKind(), first, req.getLayoutConstraint());
-          printRequirement(substReq);
-        }
+
+        // We don't substitute type for the printed requirement so that the
+        // printed requirement agrees with separately reported generic parameters.
+        printRequirement(req);
         Printer.printStructurePost(PrintStructureKind::GenericRequirement);
       }
     }

test/IDE/print_ast_tc_decls.swift

@@ -1358,7 +1358,7 @@ protocol ProtocolWithWhereClauseAndAssoc : QuxProtocol where Qux == Int {
 
   // FIXME: this same type requirement with Self should be printed here
   associatedtype A2 : QuxProtocol where A2.Qux == Self
-// PREFER_TYPE_REPR_PRINTING-DAG: {{^}}  associatedtype A2 : QuxProtocol where Self.A2.Qux == Self{{$}}
+// PREFER_TYPE_REPR_PRINTING-DAG: {{^}}  associatedtype A2 : QuxProtocol where Self == Self.A2.Qux{{$}}
 }
 
 #if true

test/IDE/print_synthesized_extensions.swift

@@ -237,21 +237,21 @@ extension S13 : P5 {
   public func foo1() {}
 }
 
-// CHECK1: <synthesized>extension <ref:Struct>S1</ref> where T : <ref:Protocol>P2</ref> {
+// CHECK1: <synthesized>extension <ref:Struct>S1</ref> where <ref:GenericTypeParam>Self</ref>.P2T1 : <ref:Protocol>P2</ref> {
 // CHECK1-NEXT:     <decl:Func>public func <loc>p2member()</loc></decl>
 // CHECK1-NEXT:     <decl:Func>public func <loc>ef1(<decl:Param>t: T</decl>)</loc></decl>
 // CHECK1-NEXT:     <decl:Func>public func <loc>ef2(<decl:Param>t: <ref:Struct>S2</ref></decl>)</loc></decl>
 // CHECK1-NEXT: }</synthesized>
 
-// CHECK2:  <synthesized>extension <ref:Struct>S1</ref> where T : <ref:Protocol>P3</ref> {
+// CHECK2:  <synthesized>extension <ref:Struct>S1</ref> where <ref:GenericTypeParam>Self</ref>.T1 : <ref:Protocol>P3</ref>  {
 // CHECK2-NEXT:     <decl:Func>public func <loc>p3Func(<decl:Param>i: <ref:Struct>Int</ref></decl>)</loc> -> <ref:Struct>Int</ref></decl>
 // CHECK2-NEXT: }</synthesized>
 
-// CHECK3:  <synthesized>extension <ref:Struct>S1</ref> where T == <ref:Struct>Int</ref> {
+// CHECK3:  <synthesized>extension <ref:Struct>S1</ref> where <ref:GenericTypeParam>Self</ref>.T1 == <ref:Struct>Int</ref>  {
 // CHECK3-NEXT:     <decl:Func>public func <loc>p1IntFunc(<decl:Param>i: <ref:Struct>Int</ref></decl>)</loc> -> <ref:Struct>Int</ref></decl>
 // CHECK3-NEXT: }</synthesized>
 
-// CHECK4:  <synthesized>extension <ref:Struct>S1</ref> where T == <ref:Struct>S9</ref><<ref:Struct>Int</ref>> {
+// CHECK4:  <synthesized>extension <ref:Struct>S1</ref> where <ref:GenericTypeParam>Self</ref>.T1 == <ref:Struct>S9</ref><<ref:Struct>Int</ref>> {
 // CHECK4-NEXT:     <decl:Func>public func <loc>S9IntFunc()</loc></decl>
 // CHECK4-NEXT: }</synthesized>