Bug: If statement initialization missing when running under llgo

[luoliwoshang]

Summary

When using gogen to generate Go code with an If statement that includes an initialization statement, the code generated under llgo is missing the initialization part. The same code works correctly when run with standard Go.

This issue is similar to #1604 (TypeSwitch initialization bug).

Environment

• llgo version: latest devel branch
• OS: macOS (Darwin 24.5.0)
• gogen: latest version

Reproduction

Expected Behavior (works with go run)

func main() {
	if x := 3; x > 1 {
		fmt.Println("OK!")
	}
}

Actual Behavior (when using llgo run)

func main() {
	if x > 1 {  // ❌ Missing "x := 3;" initialization
		fmt.Println("OK!")
	}
}

Minimal Reproduction Code

package main

import (
	"bytes"
	"fmt"
	"go/token"

	"github.com/goplus/gogen"
	"github.com/goplus/gogen/packages"
)

func ctxRef(pkg *gogen.Package, name string) gogen.Ref {
	_, o := pkg.CB().Scope().LookupParent(name, token.NoPos)
	return o
}

func main() {
	fset := token.NewFileSet()
	imp := packages.NewImporter(fset)
	conf := &gogen.Config{Fset: fset, Importer: imp}
	pkg := gogen.NewPackage("", "main", conf)

	pkg.NewFunc(nil, "main", nil, nil, false).BodyStart(pkg).
		If().DefineVarStart(0, "x").Val(3).EndInit(1).
		Val(ctxRef(pkg, "x")).Val(1).BinaryOp(token.GTR).Then().
		Val(pkg.Import("fmt").Ref("Println")).Val("OK!").Call(1).EndStmt().
		End().
		End()

	var buf bytes.Buffer
	pkg.WriteTo(&buf)
	result := buf.String()

	expected := `package main

import "fmt"

func main() {
	if x := 3; x > 1 {
		fmt.Println("OK!")
	}
}
`

	fmt.Println("Generated code:")
	fmt.Println(result)
	fmt.Println("\nExpected code:")
	fmt.Println(expected)

	if result != expected {
		fmt.Println("\n❌ BUG: If statement initialization is missing!")
	} else {
		fmt.Println("\n✅ PASS")
	}
}

Steps to Reproduce

1. Save the code above as bug_if_init.go
2. Run with standard Go: go run bug_if_init.go
   • ✅ Output: "PASS"
3. Run with llgo: llgo run bug_if_init.go
   • ❌ Output: "BUG: If statement initialization is missing!"

Root Cause Analysis

The initialization statement (DefineVarStart()...EndInit() call) is processed correctly by standard Go but appears to be ignored or lost when the code is executed under llgo runtime.

Impact

This bug affects any code generation that relies on If statement initialization, which is a common Go language feature (e.g., if err := foo(); err != nil { ... }).

Related Issues

• Bug: TypeSwitch initialization statement missing when running under llgo when use gogen #1604 - Similar issue with TypeSwitch initialization statement missing
  • Both issues involve initialization statements being lost in control flow structures
  • Suggests there may be a common root cause in how llgo handles statement initialization

Related Test

This bug was discovered while porting package_test.go tests to llgo. The test TestIf fails under llgo but passes under standard Go.

[luoliwoshang]

func a() []int {
	var t = T{data: []int{1, 2}}
	a := t.data
	t.data = []int{1, 2, 3}
	return a
}

_command-line-arguments.a:
0000000100004960	sub	sp, sp, #0x40
0000000100004964	stp	x29, x30, [sp, #0x30]
0000000100004968	str	x8, [sp, #0x10]
000000010000496c	str	xzr, [sp, #0x18]
0000000100004970	str	xzr, [sp, #0x20]
0000000100004974	str	xzr, [sp, #0x28]
0000000100004978	mov	w8, #0x10
000000010000497c	mov	x0, x8
0000000100004980	bl	"_github.com/goplus/llgo/runtime/internal/runtime.AllocZ"
0000000100004984	mov	w8, #0x1
0000000100004988	str	x8, [sp]
000000010000498c	str	x8, [x0]
0000000100004990	mov	w8, #0x2
0000000100004994	str	x8, [sp, #0x8]
0000000100004998	str	x8, [x0, #0x8]
000000010000499c	str	x0, [sp, #0x18]
00000001000049a0	str	x8, [sp, #0x20]
00000001000049a4	str	x8, [sp, #0x28]
00000001000049a8	mov	w8, #0x18
00000001000049ac	mov	x0, x8
00000001000049b0	bl	"_github.com/goplus/llgo/runtime/internal/runtime.AllocZ"
00000001000049b4	ldr	x10, [sp]
00000001000049b8	ldr	x8, [sp, #0x8]
00000001000049bc	ldr	x9, [sp, #0x10]
00000001000049c0	str	x10, [x0]
00000001000049c4	str	x8, [x0, #0x8]
00000001000049c8	mov	w8, #0x3
00000001000049cc	str	x8, [x0, #0x10]
00000001000049d0	str	x0, [sp, #0x18]
00000001000049d4	str	x8, [sp, #0x20]
00000001000049d8	str	x8, [sp, #0x28]
00000001000049dc	ldur	q0, [sp, #0x18]
00000001000049e0	str	q0, [x9]
00000001000049e4	ldr	x8, [sp, #0x28]
00000001000049e8	str	x8, [x9, #0x10]
00000001000049ec	ldp	x29, x30, [sp, #0x30]
00000001000049f0	add	sp, sp, #0x40
00000001000049f4	ret