swift-api-digester: teach the tool to output constructors' parameter type changes.

test/api-digester/Inputs/cake1.swift

@@ -1,4 +1,5 @@
 public struct S1 {
-  mutating public func foo1() {}
+  public init(_ : Int) {}
+  public func foo1() {}
   mutating public func foo2() {}
 }

test/api-digester/Inputs/cake2.swift

@@ -0,0 +1,5 @@
+public struct S1 {
+  public init(_ : Double) {}
+  mutating public func foo1() {}
+  mutating public func foo2() {}
+}

test/api-digester/Outputs/Cake.txt

@@ -6,6 +6,7 @@
 ==================================================== Renamed Decls ====================================================
 
 ==================================================== Type Changes ====================================================
+Constructor S1.init(_:) has 1st parameter type change from Int to Double
 
 ==================================================== Decl Attribute changes ====================================================
-FuncS1.foo1() is now mutating
+Func S1.foo1() is now mutating

test/api-digester/compare-dump.swift

@@ -1,9 +1,9 @@
 // RUN: rm -rf %t.mod && mkdir -p %t.mod
 // RUN: rm -rf %t.sdk && mkdir -p %t.sdk
 // RUN: rm -rf %t.module-cache && mkdir -p %t.module-cache
-// RUN: %swift -emit-module -o %t.mod/cake.swiftmodule %S/Inputs/cake.swift -parse-as-library
 // RUN: %swift -emit-module -o %t.mod/cake1.swiftmodule %S/Inputs/cake1.swift -parse-as-library
-// RUN: %api-digester -dump-sdk -module cake -o %t.dump.json -module-cache-path %t.module-cache -sdk %t.sdk -swift-version 3.0 -I %t.mod
+// RUN: %swift -emit-module -o %t.mod/cake2.swiftmodule %S/Inputs/cake2.swift -parse-as-library
 // RUN: %api-digester -dump-sdk -module cake1 -o %t.dump1.json -module-cache-path %t.module-cache -sdk %t.sdk -swift-version 3.0 -I %t.mod
-// RUN: %api-digester -diagnose-sdk --input-paths %t.dump.json -input-paths %t.dump1.json > %t.result
+// RUN: %api-digester -dump-sdk -module cake2 -o %t.dump2.json -module-cache-path %t.module-cache -sdk %t.sdk -swift-version 3.0 -I %t.mod
+// RUN: %api-digester -diagnose-sdk --input-paths %t.dump1.json -input-paths %t.dump2.json > %t.result
 // RUN: diff -u %S/Outputs/Cake.txt %t.result

tools/swift-api-digester/swift-api-digester.cpp

@@ -668,6 +668,7 @@ class SDKNodeAbstractFunc : public SDKNodeDecl {
   Optional<uint8_t> getSelfIndexOptional() const { return SelfIndex; }
   bool hasSelfIndex() const { return SelfIndex.hasValue(); }
   static bool classof(const SDKNode *N);
+  static StringRef getTypeRoleDescription(unsigned Index);
 };
 
 bool SDKNodeAbstractFunc::classof(const SDKNode *N) {
@@ -689,10 +690,9 @@ class SDKNodeFunction : public SDKNodeAbstractFunc {
                                                        SDKNodeKind::Function) {}
   SDKNode *getReturnType() { return (*getChildBegin()).get(); }
   static bool classof(const SDKNode *N);
-  static StringRef getTypeRoleDescription(unsigned Index);
 };
 
-StringRef SDKNodeFunction::getTypeRoleDescription(unsigned Index) {
+StringRef SDKNodeAbstractFunc::getTypeRoleDescription(unsigned Index) {
   if (Index == 0) {
     return InsertToBuffer("return");
   } else if (Index == 1) {
@@ -2814,7 +2814,7 @@ bool DiagnosisEmitter::DeclAttrDiag::operator<(DeclAttrDiag Other) const {
 }
 
 void DiagnosisEmitter::DeclAttrDiag::output() const {
-  llvm::outs() << Kind << "" << printName(DeclName) << " is now " <<
+  llvm::outs() << Kind << " " << printName(DeclName) << " is now " <<
     printDiagKeyword(AttrName) << "\n";
 }
 
@@ -2867,10 +2867,11 @@ void DiagnosisEmitter::visitType(SDKNodeType *Node) {
     auto *Count = UpdateMap.findUpdateCounterpart(Node)->getAs<SDKNodeType>();
     StringRef Descriptor;
     switch (Parent->getKind()) {
+    case SDKNodeKind::Constructor:
     case SDKNodeKind::Function:
     case SDKNodeKind::Var:
-      Descriptor = Parent->getKind() == SDKNodeKind::Function ?
-        SDKNodeFunction::getTypeRoleDescription(Parent->getChildIndex(Node)) :
+      Descriptor = isa<SDKNodeAbstractFunc>(Parent) ?
+        SDKNodeAbstractFunc::getTypeRoleDescription(Parent->getChildIndex(Node)) :
         InsertToBuffer("declared");
       TypeChangedDecls.Diags.emplace_back(Parent->getDeclKind(),
                                           Parent->getFullyQualifiedName(),