terraform: nodeExpandModule must check experiments on moduleCtx

Previously we were incorrectly checking for the experiment being enabled
on the global EvalContext, but that doesn't make sense because experiments
are explicitly module-specific.

Now we'll ask the question separately for each module so we can use the
module-scoped EvalContext.

internal/terraform/node_module_expand.go

@@ -107,20 +107,21 @@ func (n *nodeExpandModule) Execute(globalCtx EvalContext, op walkOperation) (dia
 	expander := globalCtx.InstanceExpander()
 	_, call := n.Addr.Call()
 
-	// Allowing unknown values in count and for_each is currently only an
-	// experimental feature. This will hopefully become the default (and only)
-	// behavior in future, if the experiment is successful.
-	//
-	// If this is false then the codepaths that handle unknown values below
-	// become unreachable, because the evaluate functions will reject unknown
-	// values as an error.
-	allowUnknown := globalCtx.LanguageExperimentActive(experiments.UnknownInstances)
-
 	// nodeExpandModule itself does not have visibility into how its ancestors
 	// were expanded, so we use the expander here to provide all possible paths
 	// to our module, and register module instances with each of them.
 	for _, module := range expander.ExpandModule(n.Addr.Parent()) {
 		moduleCtx := evalContextForModuleInstance(globalCtx, module)
+
+		// Allowing unknown values in count and for_each is currently only an
+		// experimental feature. This will hopefully become the default (and only)
+		// behavior in future, if the experiment is successful.
+		//
+		// If this is false then the codepaths that handle unknown values below
+		// become unreachable, because the evaluate functions will reject unknown
+		// values as an error.
+		allowUnknown := moduleCtx.LanguageExperimentActive(experiments.UnknownInstances)
+
 		switch {
 		case n.ModuleCall.Count != nil:
 			count, ctDiags := evaluateCountExpression(n.ModuleCall.Count, moduleCtx, allowUnknown)