go get github.com/zclconf/go-cty@v1.5.1

go.mod

@@ -127,7 +127,7 @@ require (
 	github.com/xanzy/ssh-agent v0.2.1
 	github.com/xiang90/probing v0.0.0-20160813154853-07dd2e8dfe18 // indirect
 	github.com/xlab/treeprint v0.0.0-20161029104018-1d6e34225557
-	github.com/zclconf/go-cty v1.5.0
+	github.com/zclconf/go-cty v1.5.1
 	github.com/zclconf/go-cty-yaml v1.0.2
 	go.uber.org/atomic v1.3.2 // indirect
 	go.uber.org/multierr v1.1.0 // indirect

go.sum

@@ -521,8 +521,8 @@ github.com/xlab/treeprint v0.0.0-20161029104018-1d6e34225557/go.mod h1:ce1O1j6Ut
 github.com/zclconf/go-cty v1.0.0/go.mod h1:xnAOWiHeOqg2nWS62VtQ7pbOu17FtxJNW8RLEih+O3s=
 github.com/zclconf/go-cty v1.1.0/go.mod h1:xnAOWiHeOqg2nWS62VtQ7pbOu17FtxJNW8RLEih+O3s=
 github.com/zclconf/go-cty v1.2.0/go.mod h1:hOPWgoHbaTUnI5k4D2ld+GRpFJSCe6bCM7m1q/N4PQ8=
-github.com/zclconf/go-cty v1.5.0 h1:U0USwJxGTnUd+dT565f92paYOlRtd201pI7+ZGW36XY=
-github.com/zclconf/go-cty v1.5.0/go.mod h1:nHzOclRkoj++EU9ZjSrZvRG0BXIWt8c7loYc0qXAFGQ=
+github.com/zclconf/go-cty v1.5.1 h1:oALUZX+aJeEBUe2a1+uD2+UTaYfEjnKFDEMRydkGvWE=
+github.com/zclconf/go-cty v1.5.1/go.mod h1:nHzOclRkoj++EU9ZjSrZvRG0BXIWt8c7loYc0qXAFGQ=
 github.com/zclconf/go-cty-yaml v1.0.2 h1:dNyg4QLTrv2IfJpm7Wtxi55ed5gLGOlPrZ6kMd51hY0=
 github.com/zclconf/go-cty-yaml v1.0.2/go.mod h1:IP3Ylp0wQpYm50IHK8OZWKMu6sPJIUgKa8XhiVHura0=
 go.opencensus.io v0.21.0/go.mod h1:mSImk1erAIZhrmZN+AvHh14ztQfjbGwt4TtuofqLduU=

vendor/github.com/zclconf/go-cty/cty/function/stdlib/collection.go

@@ -762,6 +762,9 @@ var MergeFunc = function.New(&function.Spec{
 		case allNull:
 			return cty.NullVal(retType), nil
 		case retType.IsMapType():
+			if len(outputMap) == 0 {
+				return cty.MapValEmpty(retType.ElementType()), nil
+			}
 			return cty.MapVal(outputMap), nil
 		case retType.IsObjectType(), retType.Equals(cty.DynamicPseudoType):
 			return cty.ObjectVal(outputMap), nil

vendor/github.com/zclconf/go-cty/cty/function/stdlib/set.go

@@ -167,7 +167,7 @@ func setOperationReturnType(args []cty.Value) (ret cty.Type, err error) {
 
 		// Do not unify types for empty dynamic pseudo typed collections. These
 		// will always convert to any other concrete type.
-		if arg.LengthInt() == 0 && ty.Equals(cty.DynamicPseudoType) {
+		if arg.IsKnown() && arg.LengthInt() == 0 && ty.Equals(cty.DynamicPseudoType) {
 			continue
 		}
 

vendor/modules.txt

@@ -611,7 +611,7 @@ github.com/xanzy/ssh-agent
 # github.com/xlab/treeprint v0.0.0-20161029104018-1d6e34225557
 ## explicit
 github.com/xlab/treeprint
-# github.com/zclconf/go-cty v1.5.0
+# github.com/zclconf/go-cty v1.5.1
 ## explicit
 github.com/zclconf/go-cty/cty
 github.com/zclconf/go-cty/cty/convert