Swift AST: add an initializer to SubstitutionMap

And let it conform to `NoReflectionChildren` to make it's debug dump in lldb nicer

Author: eeckstein

SwiftCompilerSources/Sources/AST/SubstitutionMap.swift

@@ -18,7 +18,7 @@ import ASTBridging
 ///
 /// Substitution maps are primarily used when performing substitutions into any entity that
 /// can reference type parameters and conformances.
-public struct SubstitutionMap: CustomStringConvertible {
+public struct SubstitutionMap: CustomStringConvertible, NoReflectionChildren {
   public let bridged: BridgedSubstitutionMap
 
   public init(bridged: BridgedSubstitutionMap) {
@@ -28,6 +28,13 @@ public struct SubstitutionMap: CustomStringConvertible {
   public init() {
     self.bridged = BridgedSubstitutionMap()
   }
+  
+  public init(genericSignature: GenericSignature, replacementTypes: [Type]) {
+    let bridgedReplTypes = replacementTypes.map { $0.bridged }
+    self.bridged = bridgedReplTypes.withBridgedArrayRef {
+      return BridgedSubstitutionMap.get(genericSignature.bridged, $0)
+    }
+  }
 
   public var description: String {
     return String(taking: bridged.getDebugDescription())

include/swift/AST/ASTBridging.h

@@ -3071,6 +3071,8 @@ struct BridgedConformanceArray {
 struct BridgedSubstitutionMap {
   uint64_t storage[1];
 
+  static SWIFT_IMPORT_UNSAFE BridgedSubstitutionMap get(BridgedGenericSignature genSig,
+                                                        BridgedArrayRef replacementTypes);
   BRIDGED_INLINE BridgedSubstitutionMap(swift::SubstitutionMap map);
   BRIDGED_INLINE swift::SubstitutionMap unbridged() const;
   BRIDGED_INLINE BridgedSubstitutionMap();

lib/AST/Bridging/MiscBridging.cpp

@@ -115,6 +115,12 @@ BridgedOwnedString BridgedConformance::getDebugDescription() const {
 static_assert(sizeof(BridgedSubstitutionMap) >= sizeof(swift::SubstitutionMap),
               "BridgedSubstitutionMap has wrong size");
 
+BridgedSubstitutionMap BridgedSubstitutionMap::get(BridgedGenericSignature genSig, BridgedArrayRef replacementTypes) {
+  return SubstitutionMap::get(genSig.unbridged(),
+                              replacementTypes.unbridged<Type>(),
+                              swift::LookUpConformanceInModule());
+}
+
 BridgedOwnedString BridgedSubstitutionMap::getDebugDescription() const {
   std::string str;
   llvm::raw_string_ostream os(str);