lang: ast, funcs: Start plumbing through the textarea

We need to get these everywhere and this is a start.

lang/funcs/structs/call.go

@@ -53,6 +53,8 @@ const (
 // The arguments are connected to the received FuncValues in such a way that
 // CallFunc emits the result of applying the function to the arguments.
 type CallFunc struct {
+	interfaces.Textarea
+
 	Type     *types.Type // the type of the result of applying the function
 	FuncType *types.Type // the type of the function
 	EdgeName string      // name of the edge used

lang/funcs/structs/composite.go

@@ -48,6 +48,8 @@ const (
 // value as a stream that depends on those inputs. It helps the list, map, and
 // struct's that fulfill the Expr interface but expressing a Func method.
 type CompositeFunc struct {
+	interfaces.Textarea
+
 	Type *types.Type // this is the type of the composite value we hold
 	Len  int         // length of list or map (if used)
 

lang/funcs/structs/const.go

@@ -44,6 +44,8 @@ const (
 
 // ConstFunc is a function that returns the constant value passed to Value.
 type ConstFunc struct {
+	interfaces.Textarea
+
 	Value    types.Value
 	NameHint string
 

lang/funcs/structs/for.go

@@ -51,6 +51,8 @@ const (
 // build a subgraph that processes each element, and in doing so we get a larger
 // function graph. This is rebuilt as necessary if the input list changes.
 type ForFunc struct {
+	interfaces.Textarea
+
 	IndexType *types.Type
 	ValueType *types.Type
 

lang/funcs/structs/forkv.go

@@ -51,6 +51,8 @@ const (
 // build a subgraph that processes each key and val, and in doing so we get a
 // larger function graph. This is rebuilt as necessary if the input map changes.
 type ForKVFunc struct {
+	interfaces.Textarea
+
 	KeyType *types.Type
 	ValType *types.Type
 

lang/funcs/structs/if.go

@@ -45,6 +45,8 @@ const (
 // IfFunc is a function that passes through the value of the correct branch
 // based on the conditional value it gets.
 type IfFunc struct {
+	interfaces.Textarea
+
 	Type *types.Type // this is the type of the if expression output we hold
 
 	init   *interfaces.Init

lang/funcs/structs/util.go

@@ -45,6 +45,8 @@ import (
 // which is implemented by &ConstFunc{}.
 func FuncValueToConstFunc(fv *full.FuncValue) interfaces.Func {
 	return &ConstFunc{
+		//Textarea: ???, // XXX: add me!
+
 		Value:    fv,
 		NameHint: "FuncValue",
 	}