Require extern functions to be declared

1 files changed, 14 insertions, 0 deletions

diff --git a/generate.go b/generate.go
index b8c6ba2..a5ddf7f 100644
--- a/generate.go
+++ b/generate.go
@@ -90,6 +90,11 @@ func generateFunction(function *functionExpr, w io.Writer) error {
 	defer func() { currentFunc = "" }()
 
 	funcs[currentFunc] = struct{}{}
+
+	if function.external {
+		return nil
+	}
+
 	localConsts[currentFunc] = map[string]string{}
 	localMuts[currentFunc] = map[string]struct{}{}
 
@@ -579,6 +584,15 @@ func (n *numberExpr) generate(w io.Writer) (string, error) {
 }
 
 func (c *callExpr) generate(w io.Writer) (string, error) {
+	_, ok := funcs[c.funcName]
+	if !ok {
+		return "", errUndeclared{
+			name:   c.funcName,
+			isFunc: true,
+			line:   c.line(),
+		}
+	}
+
 	ret := allocReg()
 
 	fmt.Fprintf(w, "%s =w call $%s(", ret, c.funcName)