Fix using Indexer as Caller.

eval/call.go

@@ -26,6 +26,17 @@ type Caller interface {
 	Call(ec *EvalCtx, args []Value)
 }
 
+func getCaller(v Value) Caller {
+	if caller, ok := v.(Caller); ok {
+		return caller
+	}
+	if indexer, ok := v.(Indexer); ok {
+		return IndexerCaller{indexer}
+	}
+	throw(fmt.Errorf("a %s is not callable", v.Kind()))
+	panic("unreachable")
+}
+
 func (ec *EvalCtx) PCall(f Caller, args []Value) (ex error) {
 	defer errutil.Catch(&ex)
 	f.Call(ec, args)

eval/compile.go

@@ -237,10 +237,7 @@ func (cp *compiler) form(n *parse.Form) Op {
 		headValues := headOp(ec)
 		headMust := ec.must(headValues, "the head of command", p)
 		headMust.mustLen(1)
-		headCaller, ok := headValues[0].(Caller)
-		if !ok {
-			headMust.error("a callable", headValues[0].Kind())
-		}
+		headCaller := getCaller(headValues[0])
 
 		// args
 		var args []Value

eval/index.go

@@ -64,3 +64,17 @@ func intIndex(idx Value) int {
 	}
 	return i
 }
+
+/*
+// CallerIndexer adapts a Caller to an Indexer.
+type CallerIndexer struct {
+	Caller
+	ec *EvalCtx
+}
+
+func (ci CallerIndexer) Index(idx Value) Value {
+	return captureOutput(ci.ec, func(ec *EvalCtx) {
+		ci.Caller.Call(ec, []Value{idx})
+	})
+}
+*/