[AST] Add a way to check whether TypeRepr is an inverse of the given invertible protocol

Author: xedin

include/swift/AST/TypeRepr.h

@@ -137,6 +137,10 @@ class alignas(1 << TypeReprAlignInBits) TypeRepr
   /// Is this type representation a protocol?
   bool isProtocolOrProtocolComposition(DeclContext *dc);
 
+  /// Is this `~<target>` representation.
+  bool isInverseOf(InvertibleProtocolKind target,
+                   DeclContext *dc);
+
   /// Is this type representation known to be invalid?
   bool isInvalid() const { return Bits.TypeRepr.Invalid; }
 

lib/AST/NameLookup.cpp

@@ -3305,6 +3305,29 @@ bool TypeRepr::isProtocolOrProtocolComposition(DeclContext *dc){
     return declsAreProtocols(directReferencesForTypeRepr(ctx.evaluator, ctx, this, dc));
 }
 
+bool TypeRepr::isInverseOf(InvertibleProtocolKind target, DeclContext *dc) {
+  if (auto inverseTypeRepr = dyn_cast<InverseTypeRepr>(this)) {
+    auto *constraint = inverseTypeRepr->getConstraint();
+
+    auto &ctx = dc->getASTContext();
+    return llvm::any_of(
+        directReferencesForTypeRepr(ctx.evaluator, ctx, constraint, dc),
+        [&](const TypeDecl *decl) {
+          if (auto *P = dyn_cast<ProtocolDecl>(decl))
+            return P->getInvertibleProtocolKind() == target;
+          return false;
+        });
+  }
+
+  if (auto *composition = dyn_cast<CompositionTypeRepr>(this)) {
+    return llvm::any_of(composition->getTypes(), [&](TypeRepr *member) {
+      return member->isInverseOf(target, dc);
+    });
+  }
+
+  return false;
+}
+
 static GenericParamList *
 createExtensionGenericParams(ASTContext &ctx,
                              ExtensionDecl *ext,