[llgo] Introduce llgoi, a REPL for Go

[pcc]

Summary

llgoi is a Go REPL based on llgo irgen and the LLVM JIT. It supports
expressions, statements, most declarations and imports, including binary
imports from the standard library and source imports from $GOPATH.

[axw]

This is great, thank you!

I wonder if we should be leaning a little more on go/parser, so we can identify and error on labeled statements, for example. I don't think we need to worry about that just now, though.

cmd/llgoi/llgoi.go

97

This should only apply to on-the-fly source packages, not ones on-disk. Perhaps add another flag to loadSourcePackage which determines whether or not to augment.

127

lowercase, for consistency

131

Can we please follow https://github.com/golang/go/wiki/CodeReviewComments#named-result-parameters, and not named results unless it's helpful documentation-wise? I'd prefer no naked returns either. "return nil, err" makes it immediately obvious what all the result values are.

283

fmt.Fprintf(&code, "package %s", pkgname)

289

fmt.Fprintf(&code, "import %q\n", pkg.Path())

313

Should this error if len(assigns)>0 and there are no new variables?

328

fmt.Fprintf(&code, " = %s\n\n", l.line)

357

fmt.Fprintf(&code, "func init() {\n\t%s}", l.line)
(is the whitespace doing anything useful? I guess if we want to log the program source)

477

Should we be making in.imports a map, to better handle duplicate imports? If you do that now, llgoi panics.

510

This would be a little neater using bufio.Scanner. I guess eventually we'd want to use GNU readline, or golang.org/x/crypto/ssh/terminal, or ...

[pcc]

Address comments

[pcc]

I wonder if we should be leaning a little more on go/parser, so we can identify and error on labeled statements, for example. I don't think we need to worry about that just now, though.

I agree that the diagnostics could be improved in many cases. Ideally I would like llgoi to be able to do all parsing/type checking of the user input up front, and treat any errors from parsing/type checking the final package as bugs, but I'm not entirely sure how best this should be achieved.

cmd/llgoi/llgoi.go

97

Ah, yes, fixed. It seemed neater for loadSourcePackage to take a copts instead.

127

Done.

131

Done.

283

Done.

289

Done.

313

Yes it should; I felt that this was more a QOI issue so I left it out of the initial version.

328

Done

357

Done.

Yes, the whitespace is semantically insignificant (except for semicolon insertion at newlines), but it is useful if we want to look at the source.

477

We should be handling a number of things of that nature better. As one other example, if you declare a variable with the same name as an import, llgoi gets confused and refuses to interpret any more lines. I figured this would be good enough for the initial version though.

510

I guess eventually we'd want to use GNU readline, or golang.org/x/crypto/ssh/terminal, or ...

Yes, or something like that. I think it would be very cool if this could do tab completion, but I couldn't find a suitable package (not to mention the details of actually computing the completions, which doesn't seem easy with the current go/types package).

[axw]

LGTM.

Will you be announcing this on golang-nuts? I think you'll make a bunch of people happy, and I can easily see it attracting more help.

[pcc]

I'll announce it soon. I would like an upstream change to land first, specifically https://go-review.googlesource.com/#/c/2137/ , as it fixes certain bugs that occur when importing source packages.

CMakeLists.txt

GOFLAGS "cc=${CMAKE_BINARY_DIR}/bin/clang"
           "cxx=${CMAKE_BINARY_DIR}/bin/clang++"
           "llgo=${CMAKE_BINARY_DIR}/bin/llgo-stage2${CMAKE_EXECUTABLE_SUFFIX}"
 )
 
 llvm_add_go_executable(cc-wrapper llvm.org/llgo/cmd/cc-wrapper DEPENDS
   cmd/cc-wrapper/main.go
 )
 
+llvm_add_go_executable(llgoi llvm.org/llgo/cmd/llgoi
+  DEPENDS libgo ${CMAKE_BINARY_DIR}/bin/llgo${CMAKE_EXECUTABLE_SUFFIX}
+          cmd/llgoi/isatty_posix.go
+          cmd/llgoi/llgoi.go
+  GOFLAGS "cc=${CMAKE_BINARY_DIR}/bin/clang"
+          "cxx=${CMAKE_BINARY_DIR}/bin/clang++"
+          "llgo=${CMAKE_BINARY_DIR}/bin/llgo${CMAKE_EXECUTABLE_SUFFIX}"
+)
+
 function(add_clobber_steps name)
   ExternalProject_Add_Step(${name} force-reconfigure
     DEPENDERS configure
     ALWAYS 1
     )
 
   ExternalProject_Add_Step(${name} clobber
     COMMAND ${CMAKE_COMMAND} -E remove_directory <BINARY_DIR>

cmd/llgoi/isatty_posix.go

+//===- isatty_posix.go - isatty implementation for POSIX ------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Implements isatty for POSIX systems.
+//
+//===----------------------------------------------------------------------===//
+
+package main
+
+// +build !windows
+
+/*
+#include <unistd.h>
+*/
+import "C"
+
+import (
+  "os"
+)
+
+func isatty(file *os.File) bool {
+  return C.isatty(C.int(file.Fd())) != 0
+}

cmd/llgoi/llgoi.go

+//===- llgoi.go - llgo-based Go REPL --------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is llgoi, a Go REPL based on llgo and the LLVM JIT.
+//
+//===----------------------------------------------------------------------===//
+
+package main
+
+import (
+  "bufio"
+  "bytes"
+  "errors"
+  "fmt"
+  "go/ast"
+  "go/build"
+  "go/parser"
+  "go/scanner"
+  "go/token"
+  "io"
+  "os"
+  "os/exec"
+  "path/filepath"
+  "runtime/debug"
+  "strconv"
+  "strings"
+  "unsafe"
+
+  "llvm.org/llgo/driver"
+  "llvm.org/llgo/irgen"
+  "llvm.org/llgo/third_party/gotools/go/types"
+  "llvm.org/llvm/bindings/go/llvm"
+)
+
+func getInstPrefix() (string, error) {
+  path, err := exec.LookPath(os.Args[0])
+  if err != nil {
+    return "", err
+  }
+
+  path, err = filepath.EvalSymlinks(path)
+  if err != nil {
+    return "", err
+  }
+
+  prefix := filepath.Join(path, "..", "..")
+  return prefix, nil
+}
+
+func llvmVersion() string {
+  return strings.Replace(llvm.Version, "svn", "", 1)
+}
+
+type line struct {
+  line     string
+  isStmt   bool
+  declName string
+  assigns  []string
+
+  parens, bracks, braces int
+}
+
+type interp struct {
+  engine llvm.ExecutionEngine
+
+  pendingLine line
+
+  copts irgen.CompilerOptions
+
+  imports []*types.Package
+  scope   map[string]types.Object
+
+  pkgmap, inputPkgmap map[string]*types.Package
+  pkgnum              int
+}
+
+func (in *interp) makeCompilerOptions() error {
+  prefix, err := getInstPrefix()
+  if err != nil {
+    return err
+  }
+
+  llvm.LoadLibraryPermanently(filepath.Join(prefix, "lib", "libgo-llgo.so"))
+
+  importPaths := []string{filepath.Join(prefix, "lib", "go", "llgo-"+llvmVersion())}
+  in.copts = irgen.CompilerOptions{
+    TargetTriple:  llvm.DefaultTargetTriple(),
+    ImportPaths:   importPaths,
+    GenerateDebug: true,
+  }
+  err = in.copts.MakeImporter()
+  if err != nil {
+    return err
+  }
+
+  origImporter := in.copts.Importer
+  in.copts.Importer = func(pkgmap map[string]*types.Package, pkgpath string) (*types.Package, error) {
+    if pkg, ok := in.inputPkgmap[pkgpath]; ok {
+      return pkg, nil
+    }
+    return origImporter(pkgmap, pkgpath)
+  }
+  return nil
+}
+
+func (in *interp) init() error {
+  in.scope = make(map[string]types.Object)
+  in.pkgmap = make(map[string]*types.Package)
+  in.inputPkgmap = make(map[string]*types.Package)
+
+  err := in.makeCompilerOptions()
+  if err != nil {
+    return err
+  }
+
+  return nil
+}
+
+func (in *interp) dispose() {
+  in.engine.Dispose()
+}
+
+func (in *interp) loadSourcePackageFromCode(pkgcode, pkgpath string, copts irgen.CompilerOptions) (*types.Package, error) {
+  fset := token.NewFileSet()
+  file, err := parser.ParseFile(fset, "<input>", pkgcode, parser.DeclarationErrors|parser.ParseComments)
+  if err != nil {
+    return nil, err
+  }
+
+  files := []*ast.File{file}
+
+  return in.loadSourcePackage(fset, files, pkgpath, copts)
+}
+
+func (in *interp) loadSourcePackage(fset *token.FileSet, files []*ast.File, pkgpath string, copts irgen.CompilerOptions) (pkg *types.Package, err error) {
+  compiler, err := irgen.NewCompiler(copts)
+  if err != nil {
+    return
+  }
+
+  module, err := compiler.Compile(fset, files, pkgpath)
+  if err != nil {
+    return
+  }
+  pkg = module.Package
+
+  if in.engine.C != nil {
+    in.engine.AddModule(module.Module)
+  } else {
+    options := llvm.NewMCJITCompilerOptions()
+    in.engine, err = llvm.NewMCJITCompiler(module.Module, options)
+    if err != nil {
+      return
+    }
+  }
+
+  importname := irgen.ManglePackagePath(pkgpath) + "..import$descriptor"
+  importglobal := module.Module.NamedGlobal(importname)
+
+  var importfunc func()
+  *(*unsafe.Pointer)(unsafe.Pointer(&importfunc)) = in.engine.PointerToGlobal(importglobal)
+
+  defer func() {
+    p := recover()
+    if p != nil {
+      err = fmt.Errorf("panic: %v\n%v", p, string(debug.Stack()))
+    }
+  }()
+  importfunc()
+  in.inputPkgmap[pkgpath] = pkg
+  return
+}
+
+func (in *interp) augmentPackageScope(pkg *types.Package) {
+  for _, obj := range in.scope {
+    pkg.Scope().Insert(obj)
+  }
+}
+
+func (l *line) append(str string, assigns []string) {
+  var s scanner.Scanner
+  fset := token.NewFileSet()
+  file := fset.AddFile("", fset.Base(), len(str))
+  s.Init(file, []byte(str), nil, 0)
+
+  _, tok, _ := s.Scan()
+  if l.line == "" {
+    switch tok {
+    case token.FOR, token.GO, token.IF, token.LBRACE, token.SELECT, token.SWITCH:
+      l.isStmt = true
+    case token.CONST, token.FUNC, token.TYPE, token.VAR:
+      var lit string
+      _, tok, lit = s.Scan()
+      if tok == token.IDENT {
+        l.declName = lit
+      }
+    }
+  }
+
+  for tok != token.EOF {
+    switch tok {
+    case token.LPAREN:
+      l.parens++
+    case token.RPAREN:
+      l.parens--
+    case token.LBRACE:
+      l.braces++
+    case token.RBRACE:
+      l.braces--
+    case token.LBRACK:
+      l.bracks++
+    case token.RBRACK:
+      l.bracks--
+    case token.DEC, token.INC,
+      token.ASSIGN, token.ADD_ASSIGN, token.SUB_ASSIGN,
+      token.MUL_ASSIGN, token.QUO_ASSIGN, token.REM_ASSIGN,
+      token.AND_ASSIGN, token.OR_ASSIGN, token.XOR_ASSIGN,
+      token.SHL_ASSIGN, token.SHR_ASSIGN, token.AND_NOT_ASSIGN:
+      if l.parens == 0 && l.bracks == 0 && l.braces == 0 {
+        l.isStmt = true
+      }
+    }
+    _, tok, _ = s.Scan()
+  }
+
+  if l.line == "" {
+    l.assigns = assigns
+  }
+  l.line += str
+}
+
+func (l *line) ready() bool {
+  return l.parens <= 0 && l.bracks <= 0 && l.braces <= 0
+}
+
+func (in *interp) readExprLine(str string, assigns []string) error {
+  in.pendingLine.append(str, assigns)
+
+  if in.pendingLine.ready() {
+    err := in.interpretLine(in.pendingLine)
+    in.pendingLine = line{}
+    return err
+  } else {
+    return nil
+  }
+}
+
+func (in *interp) interpretLine(l line) error {
+  pkgname := fmt.Sprintf("input%05d", in.pkgnum)
+  in.pkgnum++
+
+  pkg := types.NewPackage(pkgname, pkgname)
+  scope := pkg.Scope()
+
+  for _, imppkg := range in.imports {
+    obj := types.NewPkgName(token.NoPos, pkg, imppkg.Name(), imppkg)
+    scope.Insert(obj)
+  }
+
+  in.augmentPackageScope(pkg)
+
+  var tv types.TypeAndValue
+  if l.declName == "" && !l.isStmt {
+    var err error
+    tv, err = types.Eval(l.line, pkg, scope)
+    if err != nil {
+      return err
+    }
+  }
+
+  var code bytes.Buffer
+  fmt.Fprintf(&code, "package %s", pkgname)
+  code.WriteString("\n\nimport __fmt__ \"fmt\"\n")
+  code.WriteString("import __os__ \"os\"\n")
+
+  for _, pkg := range in.imports {
+    fmt.Fprintf(&code, "import %q\n", pkg.Path())
+  }
+
+  if l.declName != "" {
+    code.WriteString(l.line)
+  } else if !l.isStmt && tv.IsValue() {
+    var typs []types.Type
+    if tuple, ok := tv.Type.(*types.Tuple); ok {
+      typs = make([]types.Type, tuple.Len())
+      for i := range typs {
+        typs[i] = tuple.At(i).Type()
+      }
+    } else {
+      typs = []types.Type{tv.Type}
+    }
+    if len(l.assigns) == 2 && tv.HasOk() {
+      typs = append(typs, types.Typ[types.Bool])
+    }
+    if len(l.assigns) != 0 && len(l.assigns) != len(typs) {
+      return errors.New("return value mismatch")
+    }
+
+    code.WriteString("var ")
+    for i := range typs {
+      if i != 0 {
+        code.WriteString(", ")
+      }
+      if len(l.assigns) != 0 && l.assigns[i] != "" {
+        if _, ok := in.scope[l.assigns[i]]; ok {
+          fmt.Fprintf(&code, "__llgoiV%d", i)
+        } else {
+          code.WriteString(l.assigns[i])
+        }
+      } else {
+        fmt.Fprintf(&code, "__llgoiV%d", i)
+      }
+    }
+    fmt.Fprintf(&code, " = %s\n\n", l.line)
+
+    code.WriteString("func init() {\n\t")
+    for i, t := range typs {
+      var varname, prefix string
+      if len(l.assigns) != 0 && l.assigns[i] != "" {
+        if _, ok := in.scope[l.assigns[i]]; ok {
+          fmt.Fprintf(&code, "\t%s = __llgoiV%d\n", l.assigns[i], i)
+        }
+        varname = l.assigns[i]
+        prefix = l.assigns[i]
+      } else {
+        varname = fmt.Sprintf("__llgoiV%d", i)
+        prefix = fmt.Sprintf("#%d", i)
+      }
+      if _, ok := t.Underlying().(*types.Interface); ok {
+        fmt.Fprintf(&code, "\t__fmt__.Printf(\"%s %s (%%T) = %%+v\\n\", %s, %s)\n", prefix, t.String(), varname, varname)
+      } else {
+        fmt.Fprintf(&code, "\t__fmt__.Printf(\"%s %s = %%+v\\n\", %s)\n", prefix, t.String(), varname)
+      }
+    }
+    code.WriteString("}")
+  } else {
+    if len(l.assigns) != 0 {
+      return errors.New("return value mismatch")
+    }
+
+    fmt.Fprintf(&code, "func init() {\n\t%s}", l.line)
+  }
+
+  copts := in.copts
+  copts.PackageCreated = in.augmentPackageScope
+  copts.DisableUnusedImportCheck = true
+  pkg, err := in.loadSourcePackageFromCode(code.String(), pkgname, copts)
+  if err != nil {
+    return err
+  }
+
+  in.imports = append(in.imports, pkg)
+
+  for _, assign := range l.assigns {
+    if assign != "" {
+      if _, ok := in.scope[assign]; !ok {
+        in.scope[assign] = pkg.Scope().Lookup(assign)
+      }
+    }
+  }
+
+  if l.declName != "" {
+    in.scope[l.declName] = pkg.Scope().Lookup(l.declName)
+  }
+
+  return nil
+}
+
+func (in *interp) maybeReadAssignment(line string, s *scanner.Scanner, initial string, base int) (bool, error) {
+  if initial == "_" {
+    initial = ""
+  }
+  assigns := []string{initial}
+
+  pos, tok, lit := s.Scan()
+  for tok == token.COMMA {
+    pos, tok, lit = s.Scan()
+    if tok != token.IDENT {
+      return false, nil
+    }
+
+    if lit == "_" {
+      lit = ""
+    }
+    assigns = append(assigns, lit)
+
+    pos, tok, lit = s.Scan()
+  }
+
+  if tok != token.DEFINE {
+    return false, nil
+  }
+
+  return true, in.readExprLine(line[int(pos)-base+2:], assigns)
+}
+
+func (in *interp) loadPackage(pkgpath string) (*types.Package, error) {
+  pkg, err := in.copts.Importer(in.pkgmap, pkgpath)
+  if err == nil {
+    return pkg, nil
+  }
+
+  buildpkg, err := build.Import(pkgpath, ".", 0)
+  if err != nil {
+    return nil, err
+  }
+  if len(buildpkg.CgoFiles) != 0 {
+    return nil, fmt.Errorf("%s: cannot load cgo package", pkgpath)
+  }
+
+  for _, imp := range buildpkg.Imports {
+    _, err := in.loadPackage(imp)
+    if err != nil {
+      return nil, err
+    }
+  }
+
+  fmt.Printf("# %s\n", pkgpath)
+
+  inputs := make([]string, len(buildpkg.GoFiles))
+  for i, file := range buildpkg.GoFiles {
+    inputs[i] = filepath.Join(buildpkg.Dir, file)
+  }
+
+  fset := token.NewFileSet()
+  files, err := driver.ParseFiles(fset, inputs)
+  if err != nil {
+    return nil, err
+  }
+
+  return in.loadSourcePackage(fset, files, pkgpath, in.copts)
+}
+
+func (in *interp) readLine(line string) error {
+  if !in.pendingLine.ready() {
+    return in.readExprLine(line, nil)
+  }
+
+  var s scanner.Scanner
+  fset := token.NewFileSet()
+  file := fset.AddFile("", fset.Base(), len(line))
+  s.Init(file, []byte(line), nil, 0)
+
+  _, tok, lit := s.Scan()
+  switch tok {
+  case token.EOF:
+    return nil
+
+  case token.IMPORT:
+    _, tok, lit = s.Scan()
+    if tok != token.STRING {
+      return errors.New("expected string literal")
+    }
+    pkgpath, err := strconv.Unquote(lit)
+    if err != nil {
+      return err
+    }
+    pkg, err := in.loadPackage(pkgpath)
+    if err != nil {
+      return err
+    }
+    in.imports = append(in.imports, pkg)
+    return nil
+
+  case token.IDENT:
+    ok, err := in.maybeReadAssignment(line, &s, lit, file.Base())
+    if err != nil {
+      return err
+    }
+    if ok {
+      return nil
+    }
+
+    fallthrough
+
+  default:
+    return in.readExprLine(line, nil)
+  }
+}
+
+func main() {
+  llvm.LinkInMCJIT()
+  llvm.InitializeNativeTarget()
+  llvm.InitializeNativeAsmPrinter()
+
+  var in interp
+  err := in.init()
+  if err != nil {
+    panic(err)
+  }
+  defer in.dispose()
+
+  tty := isatty(os.Stdin)
+
+  r := bufio.NewReader(os.Stdin)
+  for {
+    if tty {
+      if in.pendingLine.ready() {
+        os.Stdout.WriteString("(llgo) ")
+      } else {
+        os.Stdout.WriteString("       ")
+      }
+    }
+    line, err := r.ReadString('\n')
+    if err == io.EOF {
+      break
+    } else if err != nil {
+      panic(err)
+    }
+
+    err = in.readLine(line)
+    if err != nil {
+      fmt.Println(err)
+    }
+  }
+
+  if tty {
+    os.Stdout.WriteString("\n")
+  }
+}

test/CMakeLists.txt

 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
   ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg
   )
 
 add_lit_testsuite(check-llgo "Running the llgo regression tests"
   ${CMAKE_CURRENT_BINARY_DIR}
   DEPENDS
     FileCheck
     count
     llgo
+    llgoi
     libgo
     not
   )
 set_target_properties(check-llgo PROPERTIES FOLDER "Tests")

test/lit.cfg

 import lit.formats
 import os
 import sys
 
 config.name = 'llgo'
-config.suffixes = ['.go']
+config.suffixes = ['.go', '.test']
 config.test_format = lit.formats.ShTest()
 config.test_source_root = config.llvm_src_root + '/tools/llgo/test'
 config.test_exec_root = config.llvm_obj_root + '/tools/llgo/test'
 config.excludes = ['Inputs']
 
 config.substitutions.append((r"\bllgo\b", config.llvm_obj_root + '/bin/llgo -static-libgo'))
+config.substitutions.append((r"\bllgoi\b", config.llvm_obj_root + '/bin/llgoi'))
 config.substitutions.append((r"\bFileCheck\b", config.llvm_obj_root + '/bin/FileCheck'))
 config.substitutions.append((r"\bcount\b", config.llvm_obj_root + '/bin/count'))
 config.substitutions.append((r"\bnot\b", config.llvm_obj_root + '/bin/not'))

test/llgoi/Inputs/src/bar/answer.go

+package bar
+
+func Answer() int {
+  return 42
+}

test/llgoi/Inputs/src/foo/answer.go

+package foo
+
+import "bar"
+
+func Answer() int {
+  return bar.Answer()
+}

test/llgoi/Inputs/src/foo_cgo/answer.go

+package foo_cgo
+
+// #include <stdint.h>
+import "C"
+
+func Answer() C.uint64_t {
+  return 42
+}

test/llgoi/arith.test

+// RUN: llgoi < %s | FileCheck %s
+
+1 + 1
+// CHECK: #0 untyped int = 2

test/llgoi/import-binary.test

+// RUN: llgoi < %s | FileCheck %s
+
+import "fmt"
+fmt.Println(1, "two", 3)
+// CHECK: 1 two 3

test/llgoi/import-source.test

+// RUN: env GOPATH=%S/Inputs llgoi < %s | FileCheck %s
+
+// make sure user symbols do not conflict with imported source package
+Answer := 1
+
+import "foo"
+// CHECK: # bar
+// CHECK: # foo
+
+foo.Answer()
+// CHECK: #0 int = 42
+
+import "foo_cgo"
+// CHECK: foo_cgo: cannot load cgo package

test/llgoi/interfaces.test

+// RUN: llgoi < %s | FileCheck %s
+
+import "errors"
+err := errors.New("foo")
+// CHECK: err error {{.*}} = foo
+
+err.(interface{Foo()})
+// CHECK: panic: interface conversion
+
+_, _ := err.(interface{Foo()})
+// CHECK: #0 interface{Foo()} (<nil>) = <nil>
+// CHECK: #1 bool = false
+
+err.(interface{Error() string})
+// CHECK: #0 interface{Error() string} {{.*}} = foo
+
+_, _ := err.(interface{Error() string})
+// CHECK: #0 interface{Error() string} {{.*}} = foo
+// CHECK: #1 bool = true

test/llgoi/maps.test

+// RUN: llgoi < %s | FileCheck %s
+
+m := make(map[int]int)
+// CHECK: m map[int]int = map[]
+
+m[0]
+// CHECK: #0 int = 0
+
+_, _ := m[0]
+// CHECK: #0 int = 0
+// CHECK: #1 bool = false
+
+func() {
+  m[0] = 1
+}()
+
+m[0]
+// CHECK: #0 int = 1
+
+_, _ := m[0]
+// CHECK: #0 int = 1
+// CHECK: #1 bool = true

test/llgoi/panic.test

+// RUN: llgoi < %s | FileCheck %s
+
+panic("msg")
+// CHECK: panic: msg
+
+import "fmt"
+func() {
+  defer func() {
+    r := recover()
+    fmt.Println("recovered", r)
+  }()
+  panic("msg")
+}()
+// CHECK-NOT: {{^}}panic:
+// CHECK: recovered msg
+// CHECK-NOT: {{^}}panic:

test/llgoi/vars.test

+// RUN: llgoi < %s 2>&1 | FileCheck %s
+
+x := 3
+// CHECK: x untyped int = 3
+
+x + x
+// CHECK: #0 int = 6
+
+x * x
+// CHECK: #0 int = 9
+
+x = 4
+x + x
+// CHECK: #0 int = 8
+
+x := true
+// CHECK: cannot assign {{.*}} to x (variable of type int)
+
+x, y := func() (int, int) {
+  return 1, 2
+}()
+// CHECK: x int = 1
+// CHECK: y int = 2
+
+x, _ = func() (int, int) {
+  return 3, 4
+}()
+x
+// CHECK: #0 int = 3