Swift SIL: add an initializer to create an empty SubstitutionMap

Author: eeckstein

SwiftCompilerSources/Sources/SIL/SubstitutionMap.swift

@@ -1,4 +1,4 @@
-//===--- PassUtils.swift - Utilities for optimization passes ---------------===//
+//===--- SubstitutionMap.swift --------------------------------------------===//
 //
 // This source file is part of the Swift.org open source project
 //
@@ -18,4 +18,8 @@ public struct SubstitutionMap {
   public init(_ bridged: BridgedSubstitutionMap) {
     self.bridged = bridged
   }
+  
+  public init() {
+    self.bridged = SubstitutionMap_getEmpty();
+  }
 }

include/swift/SIL/SILBridging.h

@@ -252,7 +252,8 @@ BridgedType SILType_getNominalFieldType(BridgedType type, SwiftInt index,
                                         BridgedFunction function);
 SwiftInt SILType_getFieldIdxOfNominalType(BridgedType type,
                                           BridgedStringRef fieldName);
-BridgedSubstitutionMap SILType_getContextSubstitutionMap(BridgedType);
+
+BridgedSubstitutionMap SubstitutionMap_getEmpty();
 
 BridgedBasicBlock SILArgument_getParent(BridgedArgument argument);
 SwiftInt SILArgument_isExclusiveIndirectParameter(BridgedArgument argument);

lib/SIL/Utils/SILBridging.cpp

@@ -489,6 +489,14 @@ SwiftInt SILType_getFieldIdxOfNominalType(BridgedType type,
   return -1;
 }
 
+//===----------------------------------------------------------------------===//
+//                            SubstitutionMap
+//===----------------------------------------------------------------------===//
+
+BridgedSubstitutionMap SubstitutionMap_getEmpty() {
+  return {SubstitutionMap().getOpaqueValue()};
+}
+
 //===----------------------------------------------------------------------===//
 //                            SILGlobalVariable
 //===----------------------------------------------------------------------===//