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Update for Go 1.19 and support generics.
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Update go.mod to indicate support for Go 1.19.

Add support for generic interfaces, i.e. interfaces that accept a type
parameter.

For example, you can now have this kind of interface:

```go
type Interface[Kind any] interface {
	DoTheThing() Kind
}
```

and if you run `impl 's StringImpl' 'Interface[string]` it will generate
the following code:

```go
func (s StringImpl) DoTheThing() string {
	// normal impl stub here
}
```

Fixes josharian#44.
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@paddycarver
paddycarver committed Jan 16, 2024
1 parent 30a6beb commit 7f70e7c
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Showing 5 changed files with 305 additions and 92 deletions.
8 changes: 5 additions & 3 deletions go.mod
View file
Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
module github.com/josharian/impl

go 1.14
go 1.19

require golang.org/x/tools v0.4.0

require (
golang.org/x/tools v0.4.0
golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 // indirect
golang.org/x/mod v0.7.0 // indirect
golang.org/x/sys v0.3.0 // indirect
)
42 changes: 0 additions & 42 deletions go.sum
View file
Original file line number Diff line number Diff line change
@@ -1,48 +1,6 @@
github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
golang.org/x/mod v0.2.0 h1:KU7oHjnv3XNWfa5COkzUifxZmxp1TyI7ImMXqFxLwvQ=
golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
golang.org/x/mod v0.7.0 h1:LapD9S96VoQRhi/GrNTqeBJFrUjs5UHCAtTlgwA5oZA=
golang.org/x/mod v0.7.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
golang.org/x/net v0.0.0-20200226121028-0de0cce0169b/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
golang.org/x/net v0.3.0/go.mod h1:MBQ8lrhLObU/6UmLb4fmbmk5OcyYmqtbGd/9yIeKjEE=
golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.3.0 h1:w8ZOecv6NaNa/zC8944JTU3vz4u6Lagfk4RPQxv92NQ=
golang.org/x/sys v0.3.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
golang.org/x/term v0.3.0/go.mod h1:q750SLmJuPmVoN1blW3UFBPREJfb1KmY3vwxfr+nFDA=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
golang.org/x/text v0.5.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
golang.org/x/tools v0.0.0-20200522201501-cb1345f3a375 h1:SjQ2+AKWgZLc1xej6WSzL+Dfs5Uyd5xcZH1mGC411IA=
golang.org/x/tools v0.0.0-20200522201501-cb1345f3a375/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=
golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
golang.org/x/tools v0.4.0 h1:7mTAgkunk3fr4GAloyyCasadO6h9zSsQZbwvcaIciV4=
golang.org/x/tools v0.4.0/go.mod h1:UE5sM2OK9E/d67R0ANs2xJizIymRP5gJU295PvKXxjQ=
golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 h1:H2TDz8ibqkAF6YGhCdN3jS9O0/s90v0rJh3X/OLHEUk=
golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2/go.mod h1:K8+ghG5WaK9qNqU5K3HdILfMLy1f3aNYFI/wnl100a8=
158 changes: 127 additions & 31 deletions impl.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,34 @@ var (
flagRecvPkg = flag.String("recvpkg", "", "package name of the receiver")
)

func parseTypeParams(in string) (string, []string, error) {
firstOpenBracket := strings.Index(in, "[")
if firstOpenBracket < 0 {
return in, []string{}, nil
}
// there are type parameters in our interface
id := in[:firstOpenBracket]
firstCloseBracket := strings.LastIndex(in, "]")
if firstCloseBracket < 0 {
// make sure we're closing our list of type parameters
return "", nil, fmt.Errorf("invalid interface name (cannot have [ without ]): %s", in)
}
if firstCloseBracket != len(in)-1 {
// make sure the first close bracket is actually the last character of the interface name
return "", nil, fmt.Errorf("invalid interface name (cannot have ] anywhere except the last character): %s", in)
}
params := strings.Split(in[firstOpenBracket+1:firstCloseBracket], ",")
typeParams := make([]string, 0, len(params))
for _, param := range params {
typeParams = append(typeParams, strings.TrimSpace(param))
}
if len(typeParams) < 1 {
// make sure if we're declaring type parameters, we declare at least one
return "", nil, fmt.Errorf("invalid interface name (cannot have empty type parameters): %s", in)
}
return id, typeParams, nil
}

// findInterface returns the import path and identifier of an interface.
// For example, given "http.ResponseWriter", findInterface returns
// "net/http", "ResponseWriter".
Expand All @@ -34,9 +62,9 @@ var (
// If an unqualified interface such as "UserDefinedInterface" is given, then
// the interface definition is presumed to be in the package within srcDir and
// findInterface returns "", "UserDefinedInterface".
func findInterface(iface string, srcDir string) (path string, id string, err error) {
if len(strings.Fields(iface)) != 1 {
return "", "", fmt.Errorf("couldn't parse interface: %s", iface)
func findInterface(iface string, srcDir string) (path string, id string, typeParams []string, err error) {
if len(strings.Fields(iface)) != 1 && !strings.Contains(iface, "[") {
return "", "", nil, fmt.Errorf("couldn't parse interface: %s", iface)
}

srcPath := filepath.Join(srcDir, "__go_impl__.go")
Expand All @@ -46,25 +74,31 @@ func findInterface(iface string, srcDir string) (path string, id string, err err
dot := strings.LastIndex(iface, ".")
// make sure iface does not end with "/" (e.g. reject net/http/)
if slash+1 == len(iface) {
return "", "", fmt.Errorf("interface name cannot end with a '/' character: %s", iface)
return "", "", nil, fmt.Errorf("interface name cannot end with a '/' character: %s", iface)
}
// make sure iface does not end with "." (e.g. reject net/http.)
if dot+1 == len(iface) {
return "", "", fmt.Errorf("interface name cannot end with a '.' character: %s", iface)
return "", "", nil, fmt.Errorf("interface name cannot end with a '.' character: %s", iface)
}
// make sure iface has at least one "." after "/" (e.g. reject net/http/httputil)
if strings.Count(iface[slash:], ".") == 0 {
return "", "", fmt.Errorf("invalid interface name: %s", iface)
return "", "", nil, fmt.Errorf("invalid interface name: %s", iface)
}
path = iface[:dot]
id = iface[dot+1:]
id, typeParams, err = parseTypeParams(id)
if err != nil {
return "", "", nil, err
}
return iface[:dot], iface[dot+1:], nil
return path, id, typeParams, nil
}

src := []byte("package hack\n" + "var i " + iface)
// If we couldn't determine the import path, goimports will
// auto fix the import path.
imp, err := imports.Process(srcPath, src, nil)
if err != nil {
return "", "", fmt.Errorf("couldn't parse interface: %s", iface)
return "", "", nil, fmt.Errorf("couldn't parse interface: %s", iface)
}

// imp should now contain an appropriate import.
Expand All @@ -78,7 +112,7 @@ func findInterface(iface string, srcDir string) (path string, id string, err err
qualified := strings.Contains(iface, ".")

if len(f.Imports) == 0 && qualified {
return "", "", fmt.Errorf("unrecognized interface: %s", iface)
return "", "", nil, fmt.Errorf("unrecognized interface: %s", iface)
}

if !qualified {
Expand All @@ -89,10 +123,22 @@ func findInterface(iface string, srcDir string) (path string, id string, err err
// var i Reader
decl := f.Decls[0].(*ast.GenDecl) // var i io.Reader
spec := decl.Specs[0].(*ast.ValueSpec) // i io.Reader
sel := spec.Type.(*ast.Ident)
id = sel.Name // Reader
if indxExpr, ok := spec.Type.(*ast.IndexExpr); ok {
// a generic type with one type parameter shows up as an IndexExpr
id = indxExpr.X.(*ast.Ident).Name
typeParams = append(typeParams, indxExpr.Index.(*ast.Ident).Name)
} else if indxListExpr, ok := spec.Type.(*ast.IndexListExpr); ok {
// a generic type with multiple type parameters shows up as an IndexListExpr
id = indxListExpr.X.(*ast.Ident).Name
for _, typeParam := range indxListExpr.Indices {
typeParams = append(typeParams, typeParam.(*ast.Ident).Name)
}
} else {
sel := spec.Type.(*ast.Ident)
id = sel.Name // Reader
}

return path, id, nil
return path, id, typeParams, nil
}

// If qualified, the code looks like:
Expand All @@ -111,10 +157,22 @@ func findInterface(iface string, srcDir string) (path string, id string, err err
}
decl := f.Decls[1].(*ast.GenDecl) // var i io.Reader
spec := decl.Specs[0].(*ast.ValueSpec) // i io.Reader
sel := spec.Type.(*ast.SelectorExpr) // io.Reader
id = sel.Sel.Name // Reader
if indxExpr, ok := spec.Type.(*ast.IndexExpr); ok {
// a generic type with one type parameter shows up as an IndexExpr
id = indxExpr.X.(*ast.SelectorExpr).Sel.Name
typeParams = append(typeParams, indxExpr.Index.(*ast.Ident).Name)
} else if indxListExpr, ok := spec.Type.(*ast.IndexListExpr); ok {
// a generic type with multiple type parameters shows up as an IndexListExpr
id = indxListExpr.X.(*ast.SelectorExpr).Sel.Name
for _, typeParam := range indxListExpr.Indices {
typeParams = append(typeParams, typeParam.(*ast.Ident).Name)
}
} else {
sel := spec.Type.(*ast.SelectorExpr) // io.Reader
id = sel.Sel.Name // Reader
}

return path, id, nil
return path, id, typeParams, nil
}

// Pkg is a parsed build.Package.
Expand All @@ -125,20 +183,27 @@ type Pkg struct {
recvPkg string
}

// Spec is ast.TypeSpec with the associated comment map.
type Spec struct {
*ast.TypeSpec
ast.CommentMap
TypeParams map[string]string
}

// typeSpec locates the *ast.TypeSpec for type id in the import path.
func typeSpec(path string, id string, srcDir string) (Pkg, *ast.TypeSpec, error) {
func typeSpec(path, id string, typeParams []string, srcDir string) (Pkg, Spec, error) {
var pkg *build.Package
var err error

if path == "" {
pkg, err = build.ImportDir(srcDir, 0)
if err != nil {
return Pkg{}, nil, fmt.Errorf("couldn't find package in %s: %v", srcDir, err)
return Pkg{}, Spec{}, fmt.Errorf("couldn't find package in %s: %v", srcDir, err)
}
} else {
pkg, err = build.Import(path, srcDir, 0)
if err != nil {
return Pkg{}, nil, fmt.Errorf("couldn't find package %s: %v", path, err)
return Pkg{}, Spec{}, fmt.Errorf("couldn't find package %s: %v", path, err)
}
}

Expand All @@ -153,21 +218,44 @@ func typeSpec(path string, id string, srcDir string) (Pkg, *ast.TypeSpec, error)
}

for _, decl := range f.Decls {
decl, ok := decl.(*ast.GenDecl)
if !ok || decl.Tok != token.TYPE {
genDecl, ok := decl.(*ast.GenDecl)
if !ok {
continue
}
decl := genDecl
if decl.Tok != token.TYPE {
continue
}
for _, spec := range decl.Specs {
spec := spec.(*ast.TypeSpec)
if spec.Name.Name != id {
continue
}
tParams := make(map[string]string, len(typeParams))
if spec.TypeParams != nil {
var specParamNames []string
for _, typeParam := range spec.TypeParams.List {
for _, name := range typeParam.Names {
if name == nil {
continue
}
specParamNames = append(specParamNames, name.Name)
}
}
if len(specParamNames) != len(typeParams) {
continue
}
for pos, specParamName := range specParamNames {
tParams[specParamName] = typeParams[pos]
}
}
p := Pkg{Package: pkg, FileSet: fset}
return p, spec, nil
s := Spec{TypeSpec: spec, TypeParams: tParams}
return p, s, nil
}
}
}
return Pkg{}, nil, fmt.Errorf("type %s not found in %s", id, path)
return Pkg{}, Spec{}, fmt.Errorf("type %s not found in %s", id, path)
}

// gofmt pretty-prints e.
Expand Down Expand Up @@ -203,9 +291,17 @@ func (p Pkg) fullType(e ast.Expr) string {
return p.gofmt(e)
}

func (p Pkg) params(field *ast.Field) []Param {
func (p Pkg) params(field *ast.Field, genericTypes map[string]string) []Param {
var params []Param
typ := p.fullType(field.Type)
var typ string
ident, ok := field.Type.(*ast.Ident)
if !ok || ident == nil {
typ = p.fullType(field.Type)
} else if genType, ok := genericTypes[ident.Name]; ok {
typ = genType
} else {
typ = p.fullType(field.Type)
}
for _, name := range field.Names {
params = append(params, Param{Name: name.Name, Type: typ})
}
Expand Down Expand Up @@ -244,12 +340,12 @@ const (
WithoutComments EmitComments = false
)

func (p Pkg) funcsig(f *ast.Field, comments EmitComments) Func {
func (p Pkg) funcsig(f *ast.Field, genericParams map[string]string, cmap ast.CommentMap, comments EmitComments) Func {
fn := Func{Name: f.Names[0].Name}
typ := f.Type.(*ast.FuncType)
if typ.Params != nil {
for _, field := range typ.Params.List {
for _, param := range p.params(field) {
for _, param := range p.params(field, genericParams) {
// only for method parameters:
// assign a blank identifier "_" to an anonymous parameter
if param.Name == "" {
Expand All @@ -261,7 +357,7 @@ func (p Pkg) funcsig(f *ast.Field, comments EmitComments) Func {
}
if typ.Results != nil {
for _, field := range typ.Results.List {
fn.Res = append(fn.Res, p.params(field)...)
fn.Res = append(fn.Res, p.params(field, genericParams)...)
}
}
if comments == WithComments && f.Doc != nil {
Expand All @@ -286,13 +382,13 @@ func funcs(iface, srcDir, recvPkg string, comments EmitComments) ([]Func, error)
}

// Locate the interface.
path, id, err := findInterface(iface, srcDir)
path, id, typeParams, err := findInterface(iface, srcDir)
if err != nil {
return nil, err
}

// Parse the package and find the interface declaration.
p, spec, err := typeSpec(path, id, srcDir)
p, spec, err := typeSpec(path, id, typeParams, srcDir)
if err != nil {
return nil, fmt.Errorf("interface %s not found: %s", iface, err)
}
Expand All @@ -319,7 +415,7 @@ func funcs(iface, srcDir, recvPkg string, comments EmitComments) ([]Func, error)
continue
}

fn := p.funcsig(fndecl, comments)
fn := p.funcsig(fndecl, spec.TypeParams, spec.CommentMap.Filter(fndecl), comments)
fns = append(fns, fn)
}
return fns, nil
Expand Down Expand Up @@ -450,7 +546,7 @@ to prevent shell globbing.
recvs := strings.Fields(recv)
receiver := recvs[len(recvs)-1] // note that this correctly handles "s *Struct" and "*Struct"
receiver = strings.TrimPrefix(receiver, "*")
pkg, _, err := typeSpec("", receiver, *flagSrcDir)
pkg, _, err := typeSpec("", receiver, nil, *flagSrcDir)
if err == nil {
recvPkg = pkg.Package.Name
}
Expand Down
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