Go2Rust

The last Go program you'll ever need!

Artwork by Bonnie Hansen

A conservative Go-to-Rust transpiler that prioritizes correctness over performance.

Usage

# Build the transpiler
go build -o go2rust ./go

# Transpile a Go file
./go2rust input.go > output.rs

# Run tests
./test.sh

External Package Handling

Go2Rust provides four modes for handling external package imports:

1. transpile (default): Recursively transpiles all dependencies to Rust

   • Pure Rust output with no Go runtime dependency
   • Currently in development
   • Uses one workspace wrapper policy across the root package and transpiled dependencies
   • Emits shared stdlib stand-ins and shared helper types in vendor/go2rust_stdlib_stubs so dependency crates agree on imported stdlib type identities

2. stub: Generates stub implementations for external packages

   • Creates placeholder Rust modules with helpful TODO comments
   • Allows you to manually implement or use Rust equivalents
   • Useful when automatic transpilation fails or when you want custom implementations
   • Stub files are generated in vendor/ directory

3. ffi: Generates FFI bridge to call Go libraries from Rust

   • Keeps Go packages as-is and generates bindings
   • Useful for packages with cgo or complex dependencies
   • Currently in development

4. none: Fails if external packages are imported

   • Useful for simple, self-contained programs
   • Ensures no external dependencies

Example

Input (Go):

package main

import "fmt"

func GetGreeting() string {
    return "Hello, World!"
}

func GetYear() int {
    return 2024
}

func main() {
    fmt.Println(GetGreeting())
    println(GetYear())
}

Output (Rust) - Single-threaded code:

use std::rc::Rc;
use std::cell::RefCell;

fn get_greeting() -> Rc<RefCell<Option<String>>> {
    return Rc::new(RefCell::new(Some("Hello, World!".to_string())));
}

fn get_year() -> Rc<RefCell<Option<i32>>> {
    return Rc::new(RefCell::new(Some(2024)));
}

fn main() {
    println!("{}", (*get_greeting().borrow().as_ref().unwrap()));
    println!("{:?}", (*get_year().borrow().as_ref().unwrap()));
}

When the transpiler detects concurrency (goroutines, channels, or async stdlib calls), it automatically uses Arc<Mutex<Option<T>>> instead for thread safety.

Philosophy

This transpiler uses a "make it work first, optimize later" approach. EVERY Go value is wrapped for safety, but the wrapper type depends on concurrency needs:

• Single-threaded code: Uses Rc<RefCell<Option<T>>> for better performance
• Concurrent code: Uses Arc<Mutex<Option<T>>> for thread safety

This ensures semantic correctness for ANY Go program, even edge cases like taking the address of function parameters. The generated code is verbose but correct. Users can optimize later.

Progress Tracking

Go Keywords (25 total)

Keyword	Status
break - Break statements	✅
└ Direct break in switch and type-switch cases	✅
case - Case clauses
└ Switch cases	✅
└ Select cases	✅
└ Type switch cases	✅
└ Type switches over temporary call results	✅
chan - Channel types	✅
└ Channel struct fields with nil checks, send/receive, len, and cap	✅
└ Package-level channel globals initialized with make	✅
const - Constants
└ Basic constants	✅
└ String constants passed to strings.Builder	✅
└ String constants in array/slice literals	✅
└ Iota enumerations	✅
└ Complex iota expressions	✅
└ Named iota-backed enum types, including struct fields, untyped literal fields, and underlying const widths	✅
└ Named integer constants passed to function and method parameters	✅
└ Named integer constants in binary expressions with typed peers	✅
└ Named integer bitwise compound assignments with constant RHS values	✅
└ External stdlib named-integer const expressions	✅
└ Cross-file package constants in compound assignments	✅
continue - Continue statements	✅
└ Unlabeled continue in for init; cond; post executes the post statement before continuing	✅
default - Default clauses
└ Switch default	✅
└ Select default	✅
defer - Defer statements	✅
└ Methods with named returns and deferred result mutation	✅
└ Named return captures in deferred map writes	✅
└ Deferred field writes honor capture renames	✅
└ Deferred nested pointer field updates	✅
└ Defer statements inside select case bodies	✅
else - Else clauses	✅
fallthrough - Fallthrough statements	✅
for - For loops
└ C-style for loops	✅
└ While-style loops	✅
└ Infinite loops	✅
└ Range loops (slice/map/string/channel, nil slices)	✅
└ Range value field access for pointer slices	✅
└ Range string values passed to string parameters, compared, used in string helpers, and appended	✅
└ Range string values reused in []string literals	✅
└ Range string values captured by closures	✅
└ Wrapped string values from map ranges compare as owned strings	✅
└ Wrapped string values from map ranges copy into scalar map values	✅
└ Range struct values passed to function and method parameters	✅
└ Range stdlib-interface slice values used in calls, assignments, type switches, and assertions	✅
└ Stdlib-interface slice values compared with nil	✅
└ Range indexes passed to Go int parameters or assigned to Go int locals	✅
└ Range over integers	✅
func - Functions
└ Basic functions	✅
└ Multiple return values	✅
└ Method definitions	✅
└ Case-distinct methods that collapse to the same Rust name on one receiver	✅
└ Reassigned function and method parameters	✅
└ Tuple return reassignment to fields and parameters	✅
└ Method calls, including receiver self-calls	✅
└ Current receiver method calls with receiver-referencing arguments	✅
└ Method calls with function-literal arguments that capture the receiver	✅
└ Cross-file receiver mutability analysis	✅
└ Wrapped call results passed as method/function arguments	✅
└ Typed nil arguments passed to package functions	✅
└ Function-valued struct field calls	✅
└ Method selectors returning function values stay method calls	✅
└ Pointer-receiver method values returned or assigned as func values	✅
└ Named function type conversions	✅
└ Cross-package named function type conversions	✅
└ Function type aliases with imported interface parameters	✅
└ Function type aliases with pointer returns	✅
└ Function literals/closures with scoped nested captures	✅
└ Function literal named result parameters	✅
└ Function variables and higher-order function values	✅
└ Function values lower as FnMut and support recursive calls	✅
└ Function values stored in map literals	✅
└ Package function selectors assigned to function fields	✅
└ Function-typed named returns and deferred assignments	✅
└ Instantiated generic function type aliases	✅
└ Focused type-parameter constraints in concrete helper signatures such as S ~[]T, T ~string	✅
└ Assignment from function return values	✅
└ Variadic functions	✅
└ Cross-file variadic function calls	✅
└ Imported transpiled package variadic calls	✅
└ Address-of selector fields passed as fixed variadic arguments	✅
go - Goroutines	✅
└ Worker pool pattern with channels	✅
└ Method receiver captures with deferred receiver calls	✅
└ Function-typed parameter captures	✅
goto - Goto statements	✅ (basic top-level label patterns)
if - If statements
└ Basic if	✅
└ If with init statement	✅
└ If-else chains	✅
import - Imports
└ Single imports	✅
└ Multiple imports	✅
└ Package aliases	✅
└ Blank imports	✅
└ Stdlib type signatures	✅
└ Stdlib method stubs from selector type information	✅
└ Stdlib pointer method calls from indexed and range receivers	✅
└ Stdlib os.File direct method stubs from external package returns	✅
└ Stdlib package function/constant/variable stubs	✅
└ Stdlib package variadic stub calls	✅
└ Stdlib package stub calls from wrapped range variables	✅
└ Stdlib package stub calls preserve pointer handle arguments	✅
└ Stdlib typed constants as indexes	✅
└ Shared stdlib stubs across transpiled dependency crates	✅
└ Shared context/channel helpers across transpiled dependency crates	✅
└ context.Context helpers implement formatting traits for generated structs and format calls	✅
└ context.Context.Err returns boxed error handles	✅
└ Stdlib concrete values passed to stdlib interface parameters	✅
└ Stdlib concrete values passed to stdlib interface parameters across transpiled package calls	✅
└ Stdlib interface map range keys passed to interface parameters	✅
└ Stdlib interface map range keys reused as map keys	✅
└ Stdlib interface field copies	✅
└ Stdlib interface selector type assertions	✅
└ Stdlib interface indexed type assertions	✅
└ Stdlib interface range-value short declarations	✅
└ Stdlib pointer field stubs without nested wrappers	✅
└ Concurrent stdlib selector string comparisons	✅
interface - Interface types
└ Interface definitions	✅
└ Empty interface{}	✅
└ Named any returns default to nil	✅
└ Selector fields returned as any preserve the interface handle	✅
└ Existing any values assigned to any fields preserve the interface handle	✅
└ Empty struct literals with any fields default to nil	✅
└ Concurrent any and local-interface fields/globals use Send + Sync trait objects	✅
└ Local interface values clone, store, return, compare, and work with slices.Contains via generated trait-object helpers	✅
└ Interface comparisons against concrete package-global pointers	✅
└ Typed constants passed to local interface parameters	✅
└ Variadic any arguments	✅
└ Interface implementations	✅
└ Type assertions	✅
└ any(x) conversions feeding type assertions	✅
└ Static any(x).(interface{...}) assertions when TypeInfo proves implementation	✅
└ Stdlib concrete pointer literals and values returned as stdlib interface types	✅
└ Stdlib interface selector type assertions	✅
└ Imported transpiled interfaces implemented by current-package concrete types	✅
└ Boxed error values asserted back to error	✅
└ Wrapped error arguments and sentinel comparisons	✅
└ Concrete values implementing error passed to error parameters	✅
└ Package-qualified stdlib concrete error variables passed to error parameters	✅
└ Error() calls on wrapped error interface values and fields	✅
└ Error selector fields returned through error results	✅
└ Error values sent, received, and returned through channels	✅
└ Error values stored, assigned, looked up, appended, and ranged through slices and maps	✅
└ Error slices allocated with make in inferred local declarations	✅
└ Structs embedding the predeclared error interface	✅
└ Type switches, including nil, selector pointer, and stdlib named-slice cases	✅
map - Map types
└ Map types	✅
└ Map literals	✅
└ Map operations (insert, delete)	✅
└ Delete through selector map fields	✅
└ Selector map fields in lookup, comma-ok, and range contexts	✅
└ Selector map field short declarations preserve map-header copy semantics	✅
└ Promoted embedded pointer map fields in replacement assignments and indexed pointer expressions	✅
└ Map assignments through captured closure variables	✅
└ Map assignment keys reused by inserted values	✅
└ Wrapped map ranges drop map borrows before loop bodies	✅
└ Wrapped map range values used as lookup/delete keys	✅
└ Owned map range keys used in comma-ok lookups	✅
└ Map access with existence check	✅
└ Comma-ok map access with typed zero values	✅
└ Wrapped call results as map lookup keys	✅
└ Pointer keys in map literals and lookups	✅
└ Pointer keys and values in make(map), address-of literal map writes, and slice-range pointer key lookups	✅
└ Pointer map values assigned from selector fields preserve handle aliasing	✅
└ Named integer values in map literals, writes, lookups, and comma-ok zero values	✅
└ Range indexes assigned into Go int map values	✅
└ Struct keys with named integer fields across split modules	✅
└ Append results assigned into map slice values	✅
└ Nested range over map slice values	✅
└ Map range slice values assigned to local slices	✅
└ Map iteration (for range)	✅
└ Map printing (sorted keys, Go 1.12+)	✅
package - Packages
└ Main package	✅
└ Library packages	✅
└ Package-level variable initialization	✅
└ Package-level error initialization	✅
└ Package-level map literal initialization	✅
└ Package-level named slice declarations	✅
└ Package-level inferred arrays of anonymous structs	✅
└ Package-level channel globals initialized with make	✅
└ Package-level pointer globals initialized from constructor calls	✅
└ Field access through package-level pointer globals	✅
└ Exported package globals from transpiled dependency crates keep their Go names and public visibility	✅
└ Method calls on exported pointer globals from transpiled dependency crates	✅
└ Init functions	✅
└ Multi-file packages with cross-file types, methods, maps, slices, and function variables	🚧
└ Package-scoped generated helpers for multi-file stdlib/time/context types	✅
└ Stdlib helper types crossing dependency crate boundaries use shared stub crate identities	✅
└ Workspace-wide wrapper selection for transpiled external packages	✅
range - Range clauses
└ Array/slice range, including nil slices	✅
└ Map range	✅
└ String range	✅
└ Range indexes assigned into Go int map values	✅
└ Range indexes passed to Go int parameters	✅
└ Range string values from slice fields in comparisons, string helpers, and append calls	✅
└ Range stdlib-interface slice values used in calls, assignments, type switches, and assertions	✅
└ Stdlib-interface slice values compared with nil	✅
└ Channel range	✅
return - Return statements
└ Single return values	✅
└ Multiple return values	✅
└ Named returns	✅
└ Slice and map literal returns	✅
select - Select statements	✅
└ Returning from select communication and default cases	✅
struct - Struct types
└ Struct definitions	✅
└ Struct literals	✅
└ Comparable struct literals in equality expressions	✅
└ Channel fields in struct literals	✅
└ Selector-qualified struct literals (pkg.Type{})	✅
└ Stdlib struct field stubs from selector type information	✅
└ Field access	✅
└ Owned selector field returns and arguments	✅
└ Owned selector field short declarations	✅
└ Selector scalar and struct fields copy with Go value semantics	✅
└ Embedded fields	✅
└ Embedded predeclared error promotion	✅
└ Embedded method promotion from transpiled dependency packages	✅
└ Anonymous structs	✅
└ Nested structs/slices/maps/interfaces and anonymous struct function boundaries	✅
└ Struct fields containing map values with any contents	✅
└ Struct tags	✅
switch - Switch statements
└ Basic switch	✅
└ Type switch	✅
└ Fallthrough	✅
type - Type definitions
└ Struct types	✅
└ Type aliases	✅
└ Type definitions	✅
└ Go type names that collide with Rust prelude types are escaped in generated Rust	✅
└ Named scalar newtypes usable across generated modules	✅
└ Named scalar equality comparisons	✅
└ Instantiated generic function type aliases	✅
└ Numeric conversions from literals and expressions	✅
└ Numeric conversions from named integer values	✅
└ Untyped constants assigned to byte-sized slots	✅
└ Named slice type definitions in methods, parameters, ranges, indexing, append, and field method arguments	✅
└ Named slice type definitions in package globals	✅
└ Interface types	✅
var - Variable declarations
└ Basic var declarations	✅
└ Package-qualified local zero values	✅
└ Package-level declarations and initializer order	✅
└ Package-level fixed and inferred array declarations	✅
└ Package-level inferred anonymous struct array declarations	✅
└ Short declarations (:=)	✅
└ Selector slice field short declarations	✅
└ Blank identifier (_)	✅
Arrays & Slices
└ Fixed arrays	✅
└ Fixed array literals with omitted trailing zero values	✅
└ Fixed array zero values above Rust's built-in Default array sizes	✅
└ Slices	✅
└ Array/slice literal elements from wrapped call results	✅
└ Array/slice/map literals passed to package functions	✅
└ Slice operations	✅
└ Append into indexed slice elements inside arrays/slices	✅
└ Append slice values into nested slices	✅
└ Assignment into nested indexed slice elements	✅
└ Tuple-return assignments into indexed slice elements	✅
└ cap on wrapped slice fields	✅
└ Range over wrapped call results and pointer-to-array targets	✅
└ Named integer values as array/slice indexes	✅
└ Parallel slice element swaps	✅
└ Parallel slice-expression assignments into wrapped fields	✅
└ Concurrent indexed byte compound assignments	✅
Operators
└ Binary operators (+, -, *, /, etc.)	✅
└ Complex nested expressions with function calls, indexing, fields, pointers, assertions, and channel receives	✅
└ Unary NOT and conditions on wrapped bools	✅
└ Concurrent binary comparisons with bare len/cap operands	✅
└ Binary len/cap operands with typed int peers	✅
└ Untyped constants compared with named and typed integer operands	✅
└ Cross-file named integer conversions from wrapped calls	✅
└ Named integer bitwise expressions and same-type ^= assignment	✅
└ Assignment operators (=, +=, etc.)	✅
└ Increment/decrement (++, --)	✅
└ Address-of (&)	✅
└ Dereference (*)	✅
Pointers
└ Pointer types (*T)	✅
└ Address-of operator	✅
└ Dereference operator	✅
└ Pointer aliasing	✅
└ Pointer receiver nil comparisons and pointer variable call arguments	✅
└ Pointer receivers stored in pointer fields	✅
└ Pointer receiver dereference assignment (*p = T{...})	✅
└ Address-of struct literals in multi-name short declarations	✅
└ Address-of composite literals passed to pointer parameters	✅
└ Address-of local values passed to pointer parameters	✅
└ Address-of selector fields passed to pointer parameters	✅
└ Pointer type assertions passed to pointer parameters	✅
└ Address-of slice elements with named integer indexes	✅
└ Address-of struct fields and slice elements	✅
└ Declared pointers to slice elements	✅
└ Field access through ranged slice pointers	✅
String Operations
└ String concatenation (+)	✅
└ String += operator	✅
└ String += from wrapped formatted string calls	✅
└ Returning string constants from string functions	✅
└ Package string constants as map keys	✅
└ String comparisons	✅
└ Byte comparisons with character literals	✅
└ Raw string literals	✅
└ len on string literals in slice bounds	✅
└ []byte/[]rune conversions from selector expressions	✅
Closures & Anonymous Functions
└ Function literals	✅
└ Closure variable capture	✅
└ Function literal named result parameters	✅
└ Struct literal field keys are excluded from closure capture	✅
└ Methods on named function types	✅
└ Recursive closure assignment through function variables	✅
└ Closures that call captured pointer receivers through func parameters	✅
└ Anonymous function calls	✅
└ Cross-file function variables	✅
└ Capture analysis framework	✅
defer - Defer statements
└ Basic defer	✅
└ Multiple defers (LIFO order)	✅
└ Defer with closures	✅
└ Defer stack management	✅

Standard Library Functions

Function	Status
Built-in functions
└ println	✅
└ len	✅
└ cap	✅
└ len/cap passed to Go int parameters	✅
└ len/cap short declarations as Go int values	✅
└ len/cap var declarations as Go int values	✅
└ min/max over ordered basic values	✅
└ append	✅
└ append expansion from selector slice fields	✅
└ copy	✅
└ make	✅
└ delete	✅
└ new	✅
fmt package
└ fmt.Println	✅
└ fmt.Printf	✅
└ fmt.Sprintf	✅
└ fmt.Sprintf("%v", selectorSlice)	✅
└ fmt.Sprintf("%s", []*T) when T implements String() string	✅
└ fmt.Errorf	✅
└ fmt.Fprintln	✅
└ fmt.Fprintf	✅
└ %w error formatting	✅
└ %T type-name formatting in errors	✅
└ Dynamic-format panic(fmt.Errorf(...))	✅
└ %+v debug and %#x alternate hex formatting	✅
└ %x/%X byte formatting	✅
strings package
└ strings.ToUpper	✅
└ strings.ToLower	✅
└ strings.TrimSpace	✅
└ strings.TrimSpace on string slice expressions	✅
└ strings.TrimSpace on []string index expressions	✅
└ strings.Title	✅
└ strings.Contains	✅
└ strings.Index / strings.LastIndex / strings.IndexAny	✅
└ strings.Count	✅
└ strings.Compare / strings.Cut	✅
└ strings.HasPrefix / strings.HasSuffix	✅
└ Dynamic strings arguments with package const separators	✅
└ strings.Split / strings.Join / strings.Fields	✅
└ strings.Replace / strings.ReplaceAll	✅
└ strings.Repeat	✅
└ strings.EqualFold	✅
└ strings.Trim / strings.TrimLeft / strings.TrimRight	✅
strconv package
└ strconv.Itoa	✅
└ strconv.Atoi	✅
└ strconv.FormatFloat / strconv.FormatInt	✅
math package
└ math.Pi / math.E	✅
└ math.Sqrt	✅
└ math.Pow	✅
└ math.Max / math.Min	✅
math/rand package
└ rand.Seed, rand.Intn, rand.Float64	✅
encoding/json package
└ json.Marshal for structs with exported basic fields	✅
└ json.Marshal for struct map[string]string fields with omitempty	✅
└ json.Marshal for named scalar, []string, and map[string][]byte struct fields	✅
encoding/base64 package
└ base64.StdEncoding.EncodeToString	✅
└ base64.StdEncoding.DecodeString	✅
crypto/sha256 package
└ sha256.Sum256	✅
net/url package
└ url.Parse	✅
regexp package
└ regexp.MustCompile + basic FindAllString (\d+ and literal matches)	✅
└ MatchString, FindStringSubmatch, and ReplaceAllString for supported patterns	✅
reflect package
└ reflect.TypeOf struct field metadata and StructTag.Get	✅
└ reflect.StructTag(string).Get conversions	✅
└ Pointer conversions to reflected struct header stand-ins	✅
unsafe package
└ unsafe.Sizeof / unsafe.Alignof for Rust representation layout	✅
└ unsafe.Sizeof in integer comparisons and conversions	✅
└ Named unsafe.Pointer definitions round-trip through uintptr and any	✅
errors package
└ errors.New	✅
└ Package-level errors.New values	✅
└ Custom error types	✅
└ Type assertions on errors	✅
└ Error handle arguments and equality comparisons	✅
flag package
└ flag.String / flag.Parse default values	✅
time package
└ time.Unix, Time.UTC, Time.Add, Time.Unix, Time.UnixNano	✅
└ time.NewTimer plus Timer.C receive and Timer.Stop	✅
└ time.After timeout channels	✅
└ time.NewTicker plus Ticker.C receive and Ticker.Stop	✅
└ time.Tick periodic channels	✅
└ time.Duration unit expressions in assignments and comparisons	✅
context package
└ context.Background, context.WithTimeout, context.WithCancelCause, Context.Done, Context.Err, cancel funcs	✅
└ context.Context formatting through generated helper Display/Debug traits	✅
os package
└ os.Args read access	✅
└ os.Create / os.Remove plus file WriteString / Close	✅
sort package
└ sort.Strings	✅
slices package
└ slices.Sort / slices.SortFunc / slices.Contains	✅
└ slices.Clone / slices.Clip	✅
sync package
└ sync.WaitGroup	✅
└ Zero-value sync.WaitGroup struct fields	✅
└ sync.Mutex	✅
└ Direct sync.Mutex.Unlock after Lock	✅
└ sync.Once	✅
└ sync.Once.Do callbacks that initialize receiver fields	✅
sync/atomic package
└ atomic.AddInt64 / atomic.LoadInt64	✅
strings (Builder)
└ strings.Builder	✅
└ Builder.WriteString with string constants	✅
└ Builder methods on short-declared strings.Builder{} values	✅

XFAIL Tests (Expected Failures)

The tests/XFAIL/ directory contains tests for features not yet implemented. These tests:

• Document the roadmap: Each XFAIL test represents a planned feature
• Enable TDD workflow: Write the Go code you want to support, then implement the transpiler
• Auto-promote when ready: If an XFAIL test starts passing, it automatically moves to the main test suite
• Fail CI on unexpected passes: Prevents accidental feature implementation without proper review

Contributing XFAIL Tests

To report an unimplemented or broken feature, create a pull request adding tests/XFAIL/feature_name/main.go with compilable, deterministic Go code.