Fix operator overloading recursive

Fixes #548

Author: antonmedv

Diff for: expr.go

@@ -200,11 +200,24 @@ func Compile(input string, ops ...Option) (*vm.Program, error) {
 	}
 
 	if len(config.Visitors) > 0 {
-		for _, v := range config.Visitors {
-			// We need to perform types check, because some visitors may rely on
-			// types information available in the tree.
-			_, _ = checker.Check(tree, config)
-			ast.Walk(&tree.Node, v)
+		for i := 0; i < 1000; i++ {
+			more := false
+			for _, v := range config.Visitors {
+				// We need to perform types check, because some visitors may rely on
+				// types information available in the tree.
+				_, _ = checker.Check(tree, config)
+
+				ast.Walk(&tree.Node, v)
+
+				if v, ok := v.(interface {
+					ShouldRepeat() bool
+				}); ok {
+					more = more || v.ShouldRepeat()
+				}
+			}
+			if !more {
+				break
+			}
 		}
 	}
 	_, err = checker.Check(tree, config)

Diff for: patcher/operator_override.go

@@ -14,6 +14,7 @@ type OperatorOverride struct {
 	Overrides []string            // List of function names to override operator with.
 	Types     conf.TypesTable     // Env types.
 	Functions conf.FunctionsTable // Env functions.
+	applied   bool                // Flag to indicate if any override was applied.
 }
 
 func (p *OperatorOverride) Visit(node *ast.Node) {
@@ -37,9 +38,14 @@ func (p *OperatorOverride) Visit(node *ast.Node) {
 		}
 		newNode.SetType(ret)
 		ast.Patch(node, newNode)
+		p.applied = true
 	}
 }
 
+func (p *OperatorOverride) ShouldRepeat() bool {
+	return p.applied
+}
+
 func (p *OperatorOverride) FindSuitableOperatorOverload(l, r reflect.Type) (reflect.Type, string, bool) {
 	t, fn, ok := p.findSuitableOperatorOverloadInFunctions(l, r)
 	if !ok {

Diff for: test/operator/issues584/issues584_test.go

@@ -0,0 +1,73 @@
+package issues584_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/expr-lang/expr"
+)
+
+type Env struct{}
+
+type Program struct {
+}
+
+func (p *Program) Foo() Value {
+	return func(e *Env) float64 {
+		return 5
+	}
+}
+
+func (p *Program) Bar() Value {
+	return func(e *Env) float64 {
+		return 100
+	}
+}
+
+func (p *Program) AndCondition(a, b Condition) Conditions {
+	return Conditions{a, b}
+}
+
+func (p *Program) AndConditions(a Conditions, b Condition) Conditions {
+	return append(a, b)
+}
+
+func (p *Program) ValueGreaterThan_float(v Value, i float64) Condition {
+	return func(e *Env) bool {
+		realized := v(e)
+		return realized > i
+	}
+}
+
+func (p *Program) ValueLessThan_float(v Value, i float64) Condition {
+	return func(e *Env) bool {
+		realized := v(e)
+		return realized < i
+	}
+}
+
+type Condition func(e *Env) bool
+type Conditions []Condition
+
+type Value func(e *Env) float64
+
+func TestIssue584(t *testing.T) {
+	code := `Foo() > 1.5 and Bar() < 200.0`
+
+	p := &Program{}
+
+	opt := []expr.Option{
+		expr.Env(p),
+		expr.Operator("and", "AndCondition", "AndConditions"),
+		expr.Operator(">", "ValueGreaterThan_float"),
+		expr.Operator("<", "ValueLessThan_float"),
+	}
+
+	program, err := expr.Compile(code, opt...)
+	assert.Nil(t, err)
+
+	state, err := expr.Run(program, p)
+	assert.Nil(t, err)
+	assert.NotNil(t, state)
+}

Diff for: test/operator/operator_test.go

@@ -216,3 +216,40 @@ func TestOperator_Polymorphic(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, 6, output)
 }
+
+func TestOperator_recursive_apply(t *testing.T) {
+	type Decimal struct {
+		Int int
+	}
+
+	env := map[string]any{
+		"add": func(a, b Decimal) Decimal {
+			return Decimal{
+				Int: a.Int + b.Int,
+			}
+		},
+		"addInt": func(a Decimal, b int) Decimal {
+			return Decimal{
+				Int: a.Int + b,
+			}
+		},
+		"a": Decimal{1},
+		"b": Decimal{2},
+		"c": Decimal{3},
+		"d": Decimal{4},
+		"e": Decimal{5},
+	}
+
+	program, err := expr.Compile(
+		`a + b + 100 + c + d + e`,
+		expr.Env(env),
+		expr.Operator("+", "add"),
+		expr.Operator("+", "addInt"),
+	)
+	require.NoError(t, err)
+	require.Equal(t, `add(add(add(addInt(add(a, b), 100), c), d), e)`, program.Node().String())
+
+	output, err := expr.Run(program, env)
+	require.NoError(t, err)
+	require.Equal(t, 115, output.(Decimal).Int)
+}