feat: add star expression type checking

This adds type checking to StarExpr. This also fixes a bug in assignment where the symbol type was updated but not the scope type associated with it.

interp/cfg.go

@@ -518,6 +518,11 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 				if updateSym {
 					sym.typ = dest.typ
 					sym.rval = src.rval
+					// As we are updating the sym type, we need to update the sc.type
+					// when the sym has an index.
+					if sym.index >= 0 {
+						sc.types[sym.index] = sym.typ.frameType()
+					}
 				}
 				n.findex = dest.findex
 				n.level = dest.level
@@ -1554,6 +1559,12 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 			default:
 				// dereference expression
 				wireChild(n)
+
+				err = check.starExpr(n.child[0])
+				if err != nil {
+					break
+				}
+
 				if c0 := n.child[0]; c0.typ.cat == valueT {
 					n.typ = &itype{cat: valueT, rtype: c0.typ.rtype.Elem()}
 				} else {

interp/interp_eval_test.go

@@ -70,6 +70,14 @@ func TestEvalArithmetic(t *testing.T) {
 	})
 }
 
+func TestEvalStar(t *testing.T) {
+	i := interp.New(interp.Options{})
+	runTests(t, i, []testCase{
+		{src: `a := &struct{A int}{1}; b := *a`, res: "{1}"},
+		{src: `a := struct{A int}{1}; b := *a`, err: "1:57: invalid operation: cannot indirect \"a\""},
+	})
+}
+
 func TestEvalAssign(t *testing.T) {
 	i := interp.New(interp.Options{})
 	runTests(t, i, []testCase{

interp/typecheck.go

@@ -106,6 +106,14 @@ func (check typecheck) addressExpr(n *node) error {
 	return nil
 }
 
+// starExpr type checks a star expression on a variable.
+func (check typecheck) starExpr(n *node) error {
+	if n.typ.TypeOf().Kind() != reflect.Ptr {
+		return n.cfgErrorf("invalid operation: cannot indirect %q", n.name())
+	}
+	return nil
+}
+
 var unaryOpPredicates = opPredicates{
 	aPos:    isNumber,
 	aNeg:    isNumber,