fix(vm): show func for safe calls in disassembly

Previously, safe builtin functions (OpCallSafe) were pushed to the stack
as constants (OpPush), causing the disassembler/debugger to display
their memory address (e.g., 0x140000...) instead of their name (e.g.,
concat).

This change updates the compiler to store the function name in debugInfo
when emitting OpCallSafe. The VM's disassembler now checks debugInfo for
OpPush arguments and displays the stored name if available.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

Author: thevilledev

compiler/compiler.go

@@ -1103,7 +1103,9 @@ func (c *compiler) BuiltinNode(node *ast.BuiltinNode) {
 		if f.Fast != nil {
 			c.emit(OpCallBuiltin1, id)
 		} else if f.Safe != nil {
-			c.emit(OpPush, c.addConstant(f.Safe))
+			id := c.addConstant(f.Safe)
+			c.emit(OpPush, id)
+			c.debugInfo[fmt.Sprintf("const_%d", id)] = node.Name
 			c.emit(OpCallSafe, len(node.Arguments))
 		} else if f.Func != nil {
 			c.emitFunction(f, len(node.Arguments))

test/issues/567/issue_test.go

@@ -0,0 +1,25 @@
+package expr_test
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/expr-lang/expr"
+	"github.com/expr-lang/expr/internal/testify/require"
+)
+
+func TestIssue567(t *testing.T) {
+	program, err := expr.Compile("concat(1..2, 3..4)")
+	require.NoError(t, err)
+
+	var buf bytes.Buffer
+	program.DisassembleWriter(&buf)
+	output := buf.String()
+
+	// Check if "concat" is mentioned in the output
+	require.True(t, strings.Contains(output, "concat"), "expected 'concat' in disassembly output")
+
+	// It should appear as a pushed constant
+	require.True(t, strings.Contains(output, "OpPush\t<4>\tconcat"), "expected 'OpPush <4> concat' in disassembly output")
+}

vm/program.go

@@ -112,6 +112,9 @@ func (program *Program) DisassembleWriter(w io.Writer) {
 			} else {
 				c = "out of range"
 			}
+			if name, ok := program.debugInfo[fmt.Sprintf("const_%d", arg)]; ok {
+				c = name
+			}
 			if r, ok := c.(*regexp.Regexp); ok {
 				c = r.String()
 			}