706 lines
16 KiB
Go
706 lines
16 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package satisfy inspects the type-checked ASTs of Go packages and
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// reports the set of discovered type constraints of the form (lhs, rhs
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// Type) where lhs is a non-trivial interface, rhs satisfies this
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// interface, and this fact is necessary for the package to be
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// well-typed.
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//
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// THIS PACKAGE IS EXPERIMENTAL AND MAY CHANGE AT ANY TIME.
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//
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// It is provided only for the gorename tool. Ideally this
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// functionality will become part of the type-checker in due course,
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// since it is computing it anyway, and it is robust for ill-typed
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// inputs, which this package is not.
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//
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package satisfy // import "golang.org/x/tools/refactor/satisfy"
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// NOTES:
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//
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// We don't care about numeric conversions, so we don't descend into
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// types or constant expressions. This is unsound because
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// constant expressions can contain arbitrary statements, e.g.
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// const x = len([1]func(){func() {
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// ...
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// }})
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//
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// TODO(adonovan): make this robust against ill-typed input.
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// Or move it into the type-checker.
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//
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// Assignability conversions are possible in the following places:
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// - in assignments y = x, y := x, var y = x.
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// - from call argument types to formal parameter types
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// - in append and delete calls
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// - from return operands to result parameter types
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// - in composite literal T{k:v}, from k and v to T's field/element/key type
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// - in map[key] from key to the map's key type
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// - in comparisons x==y and switch x { case y: }.
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// - in explicit conversions T(x)
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// - in sends ch <- x, from x to the channel element type
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// - in type assertions x.(T) and switch x.(type) { case T: }
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//
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// The results of this pass provide information equivalent to the
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// ssa.MakeInterface and ssa.ChangeInterface instructions.
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import (
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"fmt"
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"go/ast"
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"go/token"
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"go/types"
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"golang.org/x/tools/go/ast/astutil"
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"golang.org/x/tools/go/types/typeutil"
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)
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// A Constraint records the fact that the RHS type does and must
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// satisify the LHS type, which is an interface.
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// The names are suggestive of an assignment statement LHS = RHS.
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type Constraint struct {
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LHS, RHS types.Type
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}
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// A Finder inspects the type-checked ASTs of Go packages and
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// accumulates the set of type constraints (x, y) such that x is
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// assignable to y, y is an interface, and both x and y have methods.
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//
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// In other words, it returns the subset of the "implements" relation
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// that is checked during compilation of a package. Refactoring tools
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// will need to preserve at least this part of the relation to ensure
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// continued compilation.
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//
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type Finder struct {
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Result map[Constraint]bool
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msetcache typeutil.MethodSetCache
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// per-Find state
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info *types.Info
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sig *types.Signature
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}
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// Find inspects a single package, populating Result with its pairs of
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// constrained types.
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//
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// The result is non-canonical and thus may contain duplicates (but this
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// tends to preserves names of interface types better).
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//
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// The package must be free of type errors, and
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// info.{Defs,Uses,Selections,Types} must have been populated by the
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// type-checker.
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//
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func (f *Finder) Find(info *types.Info, files []*ast.File) {
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if f.Result == nil {
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f.Result = make(map[Constraint]bool)
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}
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f.info = info
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for _, file := range files {
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for _, d := range file.Decls {
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switch d := d.(type) {
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case *ast.GenDecl:
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if d.Tok == token.VAR { // ignore consts
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for _, spec := range d.Specs {
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f.valueSpec(spec.(*ast.ValueSpec))
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}
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}
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case *ast.FuncDecl:
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if d.Body != nil {
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f.sig = f.info.Defs[d.Name].Type().(*types.Signature)
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f.stmt(d.Body)
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f.sig = nil
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}
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}
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}
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}
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f.info = nil
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}
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var (
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tInvalid = types.Typ[types.Invalid]
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tUntypedBool = types.Typ[types.UntypedBool]
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tUntypedNil = types.Typ[types.UntypedNil]
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)
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// exprN visits an expression in a multi-value context.
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func (f *Finder) exprN(e ast.Expr) types.Type {
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typ := f.info.Types[e].Type.(*types.Tuple)
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switch e := e.(type) {
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case *ast.ParenExpr:
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return f.exprN(e.X)
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case *ast.CallExpr:
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// x, err := f(args)
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sig := f.expr(e.Fun).Underlying().(*types.Signature)
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f.call(sig, e.Args)
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case *ast.IndexExpr:
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// y, ok := x[i]
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x := f.expr(e.X)
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f.assign(f.expr(e.Index), x.Underlying().(*types.Map).Key())
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case *ast.TypeAssertExpr:
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// y, ok := x.(T)
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f.typeAssert(f.expr(e.X), typ.At(0).Type())
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case *ast.UnaryExpr: // must be receive <-
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// y, ok := <-x
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f.expr(e.X)
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default:
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panic(e)
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}
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return typ
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}
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func (f *Finder) call(sig *types.Signature, args []ast.Expr) {
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if len(args) == 0 {
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return
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}
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// Ellipsis call? e.g. f(x, y, z...)
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if _, ok := args[len(args)-1].(*ast.Ellipsis); ok {
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for i, arg := range args {
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// The final arg is a slice, and so is the final param.
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f.assign(sig.Params().At(i).Type(), f.expr(arg))
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}
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return
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}
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var argtypes []types.Type
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// Gather the effective actual parameter types.
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if tuple, ok := f.info.Types[args[0]].Type.(*types.Tuple); ok {
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// f(g()) call where g has multiple results?
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f.expr(args[0])
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// unpack the tuple
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for i := 0; i < tuple.Len(); i++ {
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argtypes = append(argtypes, tuple.At(i).Type())
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}
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} else {
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for _, arg := range args {
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argtypes = append(argtypes, f.expr(arg))
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}
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}
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// Assign the actuals to the formals.
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if !sig.Variadic() {
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for i, argtype := range argtypes {
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f.assign(sig.Params().At(i).Type(), argtype)
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}
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} else {
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// The first n-1 parameters are assigned normally.
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nnormals := sig.Params().Len() - 1
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for i, argtype := range argtypes[:nnormals] {
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f.assign(sig.Params().At(i).Type(), argtype)
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}
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// Remaining args are assigned to elements of varargs slice.
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tElem := sig.Params().At(nnormals).Type().(*types.Slice).Elem()
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for i := nnormals; i < len(argtypes); i++ {
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f.assign(tElem, argtypes[i])
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}
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}
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}
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func (f *Finder) builtin(obj *types.Builtin, sig *types.Signature, args []ast.Expr, T types.Type) types.Type {
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switch obj.Name() {
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case "make", "new":
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// skip the type operand
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for _, arg := range args[1:] {
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f.expr(arg)
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}
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case "append":
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s := f.expr(args[0])
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if _, ok := args[len(args)-1].(*ast.Ellipsis); ok && len(args) == 2 {
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// append(x, y...) including append([]byte, "foo"...)
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f.expr(args[1])
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} else {
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// append(x, y, z)
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tElem := s.Underlying().(*types.Slice).Elem()
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for _, arg := range args[1:] {
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f.assign(tElem, f.expr(arg))
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}
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}
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case "delete":
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m := f.expr(args[0])
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k := f.expr(args[1])
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f.assign(m.Underlying().(*types.Map).Key(), k)
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default:
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// ordinary call
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f.call(sig, args)
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}
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return T
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}
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func (f *Finder) extract(tuple types.Type, i int) types.Type {
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if tuple, ok := tuple.(*types.Tuple); ok && i < tuple.Len() {
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return tuple.At(i).Type()
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}
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return tInvalid
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}
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func (f *Finder) valueSpec(spec *ast.ValueSpec) {
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var T types.Type
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if spec.Type != nil {
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T = f.info.Types[spec.Type].Type
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}
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switch len(spec.Values) {
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case len(spec.Names): // e.g. var x, y = f(), g()
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for _, value := range spec.Values {
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v := f.expr(value)
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if T != nil {
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f.assign(T, v)
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}
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}
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case 1: // e.g. var x, y = f()
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tuple := f.exprN(spec.Values[0])
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for i := range spec.Names {
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if T != nil {
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f.assign(T, f.extract(tuple, i))
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}
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}
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}
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}
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// assign records pairs of distinct types that are related by
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// assignability, where the left-hand side is an interface and both
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// sides have methods.
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//
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// It should be called for all assignability checks, type assertions,
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// explicit conversions and comparisons between two types, unless the
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// types are uninteresting (e.g. lhs is a concrete type, or the empty
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// interface; rhs has no methods).
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//
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func (f *Finder) assign(lhs, rhs types.Type) {
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if types.Identical(lhs, rhs) {
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return
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}
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if !isInterface(lhs) {
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return
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}
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if f.msetcache.MethodSet(lhs).Len() == 0 {
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return
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}
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if f.msetcache.MethodSet(rhs).Len() == 0 {
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return
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}
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// record the pair
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f.Result[Constraint{lhs, rhs}] = true
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}
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// typeAssert must be called for each type assertion x.(T) where x has
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// interface type I.
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func (f *Finder) typeAssert(I, T types.Type) {
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// Type assertions are slightly subtle, because they are allowed
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// to be "impossible", e.g.
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//
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// var x interface{f()}
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// _ = x.(interface{f()int}) // legal
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//
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// (In hindsight, the language spec should probably not have
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// allowed this, but it's too late to fix now.)
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//
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// This means that a type assert from I to T isn't exactly a
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// constraint that T is assignable to I, but for a refactoring
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// tool it is a conditional constraint that, if T is assignable
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// to I before a refactoring, it should remain so after.
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if types.AssignableTo(T, I) {
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f.assign(I, T)
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}
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}
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// compare must be called for each comparison x==y.
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func (f *Finder) compare(x, y types.Type) {
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if types.AssignableTo(x, y) {
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f.assign(y, x)
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} else if types.AssignableTo(y, x) {
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f.assign(x, y)
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}
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}
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// expr visits a true expression (not a type or defining ident)
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// and returns its type.
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func (f *Finder) expr(e ast.Expr) types.Type {
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tv := f.info.Types[e]
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if tv.Value != nil {
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return tv.Type // prune the descent for constants
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}
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// tv.Type may be nil for an ast.Ident.
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switch e := e.(type) {
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case *ast.BadExpr, *ast.BasicLit:
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// no-op
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case *ast.Ident:
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// (referring idents only)
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if obj, ok := f.info.Uses[e]; ok {
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return obj.Type()
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}
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if e.Name == "_" { // e.g. "for _ = range x"
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return tInvalid
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}
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panic("undefined ident: " + e.Name)
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case *ast.Ellipsis:
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if e.Elt != nil {
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f.expr(e.Elt)
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}
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case *ast.FuncLit:
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saved := f.sig
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f.sig = tv.Type.(*types.Signature)
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f.stmt(e.Body)
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f.sig = saved
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case *ast.CompositeLit:
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switch T := deref(tv.Type).Underlying().(type) {
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case *types.Struct:
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for i, elem := range e.Elts {
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if kv, ok := elem.(*ast.KeyValueExpr); ok {
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f.assign(f.info.Uses[kv.Key.(*ast.Ident)].Type(), f.expr(kv.Value))
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} else {
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f.assign(T.Field(i).Type(), f.expr(elem))
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}
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}
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case *types.Map:
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for _, elem := range e.Elts {
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elem := elem.(*ast.KeyValueExpr)
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f.assign(T.Key(), f.expr(elem.Key))
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f.assign(T.Elem(), f.expr(elem.Value))
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}
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case *types.Array, *types.Slice:
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tElem := T.(interface {
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Elem() types.Type
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}).Elem()
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for _, elem := range e.Elts {
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if kv, ok := elem.(*ast.KeyValueExpr); ok {
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// ignore the key
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f.assign(tElem, f.expr(kv.Value))
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} else {
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f.assign(tElem, f.expr(elem))
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}
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}
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default:
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panic("unexpected composite literal type: " + tv.Type.String())
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}
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case *ast.ParenExpr:
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f.expr(e.X)
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case *ast.SelectorExpr:
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if _, ok := f.info.Selections[e]; ok {
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f.expr(e.X) // selection
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} else {
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return f.info.Uses[e.Sel].Type() // qualified identifier
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}
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case *ast.IndexExpr:
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x := f.expr(e.X)
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i := f.expr(e.Index)
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if ux, ok := x.Underlying().(*types.Map); ok {
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f.assign(ux.Key(), i)
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}
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case *ast.SliceExpr:
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f.expr(e.X)
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if e.Low != nil {
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f.expr(e.Low)
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}
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if e.High != nil {
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f.expr(e.High)
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}
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if e.Max != nil {
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f.expr(e.Max)
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}
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case *ast.TypeAssertExpr:
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x := f.expr(e.X)
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f.typeAssert(x, f.info.Types[e.Type].Type)
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case *ast.CallExpr:
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if tvFun := f.info.Types[e.Fun]; tvFun.IsType() {
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// conversion
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arg0 := f.expr(e.Args[0])
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f.assign(tvFun.Type, arg0)
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} else {
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// function call
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if id, ok := unparen(e.Fun).(*ast.Ident); ok {
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if obj, ok := f.info.Uses[id].(*types.Builtin); ok {
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sig := f.info.Types[id].Type.(*types.Signature)
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return f.builtin(obj, sig, e.Args, tv.Type)
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}
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}
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// ordinary call
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f.call(f.expr(e.Fun).Underlying().(*types.Signature), e.Args)
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}
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case *ast.StarExpr:
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f.expr(e.X)
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case *ast.UnaryExpr:
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f.expr(e.X)
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case *ast.BinaryExpr:
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x := f.expr(e.X)
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y := f.expr(e.Y)
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if e.Op == token.EQL || e.Op == token.NEQ {
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f.compare(x, y)
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}
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case *ast.KeyValueExpr:
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f.expr(e.Key)
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f.expr(e.Value)
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case *ast.ArrayType,
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*ast.StructType,
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*ast.FuncType,
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*ast.InterfaceType,
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*ast.MapType,
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*ast.ChanType:
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panic(e)
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}
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if tv.Type == nil {
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panic(fmt.Sprintf("no type for %T", e))
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}
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return tv.Type
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}
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func (f *Finder) stmt(s ast.Stmt) {
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switch s := s.(type) {
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case *ast.BadStmt,
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*ast.EmptyStmt,
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*ast.BranchStmt:
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// no-op
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case *ast.DeclStmt:
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d := s.Decl.(*ast.GenDecl)
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if d.Tok == token.VAR { // ignore consts
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for _, spec := range d.Specs {
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f.valueSpec(spec.(*ast.ValueSpec))
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}
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}
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case *ast.LabeledStmt:
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f.stmt(s.Stmt)
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case *ast.ExprStmt:
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f.expr(s.X)
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case *ast.SendStmt:
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ch := f.expr(s.Chan)
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val := f.expr(s.Value)
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f.assign(ch.Underlying().(*types.Chan).Elem(), val)
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case *ast.IncDecStmt:
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f.expr(s.X)
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case *ast.AssignStmt:
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switch s.Tok {
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case token.ASSIGN, token.DEFINE:
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// y := x or y = x
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var rhsTuple types.Type
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if len(s.Lhs) != len(s.Rhs) {
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rhsTuple = f.exprN(s.Rhs[0])
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}
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for i := range s.Lhs {
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var lhs, rhs types.Type
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if rhsTuple == nil {
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rhs = f.expr(s.Rhs[i]) // 1:1 assignment
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} else {
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rhs = f.extract(rhsTuple, i) // n:1 assignment
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}
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if id, ok := s.Lhs[i].(*ast.Ident); ok {
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if id.Name != "_" {
|
|
if obj, ok := f.info.Defs[id]; ok {
|
|
lhs = obj.Type() // definition
|
|
}
|
|
}
|
|
}
|
|
if lhs == nil {
|
|
lhs = f.expr(s.Lhs[i]) // assignment
|
|
}
|
|
f.assign(lhs, rhs)
|
|
}
|
|
|
|
default:
|
|
// y op= x
|
|
f.expr(s.Lhs[0])
|
|
f.expr(s.Rhs[0])
|
|
}
|
|
|
|
case *ast.GoStmt:
|
|
f.expr(s.Call)
|
|
|
|
case *ast.DeferStmt:
|
|
f.expr(s.Call)
|
|
|
|
case *ast.ReturnStmt:
|
|
formals := f.sig.Results()
|
|
switch len(s.Results) {
|
|
case formals.Len(): // 1:1
|
|
for i, result := range s.Results {
|
|
f.assign(formals.At(i).Type(), f.expr(result))
|
|
}
|
|
|
|
case 1: // n:1
|
|
tuple := f.exprN(s.Results[0])
|
|
for i := 0; i < formals.Len(); i++ {
|
|
f.assign(formals.At(i).Type(), f.extract(tuple, i))
|
|
}
|
|
}
|
|
|
|
case *ast.SelectStmt:
|
|
f.stmt(s.Body)
|
|
|
|
case *ast.BlockStmt:
|
|
for _, s := range s.List {
|
|
f.stmt(s)
|
|
}
|
|
|
|
case *ast.IfStmt:
|
|
if s.Init != nil {
|
|
f.stmt(s.Init)
|
|
}
|
|
f.expr(s.Cond)
|
|
f.stmt(s.Body)
|
|
if s.Else != nil {
|
|
f.stmt(s.Else)
|
|
}
|
|
|
|
case *ast.SwitchStmt:
|
|
if s.Init != nil {
|
|
f.stmt(s.Init)
|
|
}
|
|
var tag types.Type = tUntypedBool
|
|
if s.Tag != nil {
|
|
tag = f.expr(s.Tag)
|
|
}
|
|
for _, cc := range s.Body.List {
|
|
cc := cc.(*ast.CaseClause)
|
|
for _, cond := range cc.List {
|
|
f.compare(tag, f.info.Types[cond].Type)
|
|
}
|
|
for _, s := range cc.Body {
|
|
f.stmt(s)
|
|
}
|
|
}
|
|
|
|
case *ast.TypeSwitchStmt:
|
|
if s.Init != nil {
|
|
f.stmt(s.Init)
|
|
}
|
|
var I types.Type
|
|
switch ass := s.Assign.(type) {
|
|
case *ast.ExprStmt: // x.(type)
|
|
I = f.expr(unparen(ass.X).(*ast.TypeAssertExpr).X)
|
|
case *ast.AssignStmt: // y := x.(type)
|
|
I = f.expr(unparen(ass.Rhs[0]).(*ast.TypeAssertExpr).X)
|
|
}
|
|
for _, cc := range s.Body.List {
|
|
cc := cc.(*ast.CaseClause)
|
|
for _, cond := range cc.List {
|
|
tCase := f.info.Types[cond].Type
|
|
if tCase != tUntypedNil {
|
|
f.typeAssert(I, tCase)
|
|
}
|
|
}
|
|
for _, s := range cc.Body {
|
|
f.stmt(s)
|
|
}
|
|
}
|
|
|
|
case *ast.CommClause:
|
|
if s.Comm != nil {
|
|
f.stmt(s.Comm)
|
|
}
|
|
for _, s := range s.Body {
|
|
f.stmt(s)
|
|
}
|
|
|
|
case *ast.ForStmt:
|
|
if s.Init != nil {
|
|
f.stmt(s.Init)
|
|
}
|
|
if s.Cond != nil {
|
|
f.expr(s.Cond)
|
|
}
|
|
if s.Post != nil {
|
|
f.stmt(s.Post)
|
|
}
|
|
f.stmt(s.Body)
|
|
|
|
case *ast.RangeStmt:
|
|
x := f.expr(s.X)
|
|
// No conversions are involved when Tok==DEFINE.
|
|
if s.Tok == token.ASSIGN {
|
|
if s.Key != nil {
|
|
k := f.expr(s.Key)
|
|
var xelem types.Type
|
|
// keys of array, *array, slice, string aren't interesting
|
|
switch ux := x.Underlying().(type) {
|
|
case *types.Chan:
|
|
xelem = ux.Elem()
|
|
case *types.Map:
|
|
xelem = ux.Key()
|
|
}
|
|
if xelem != nil {
|
|
f.assign(xelem, k)
|
|
}
|
|
}
|
|
if s.Value != nil {
|
|
val := f.expr(s.Value)
|
|
var xelem types.Type
|
|
// values of strings aren't interesting
|
|
switch ux := x.Underlying().(type) {
|
|
case *types.Array:
|
|
xelem = ux.Elem()
|
|
case *types.Chan:
|
|
xelem = ux.Elem()
|
|
case *types.Map:
|
|
xelem = ux.Elem()
|
|
case *types.Pointer: // *array
|
|
xelem = deref(ux).(*types.Array).Elem()
|
|
case *types.Slice:
|
|
xelem = ux.Elem()
|
|
}
|
|
if xelem != nil {
|
|
f.assign(xelem, val)
|
|
}
|
|
}
|
|
}
|
|
f.stmt(s.Body)
|
|
|
|
default:
|
|
panic(s)
|
|
}
|
|
}
|
|
|
|
// -- Plundered from golang.org/x/tools/go/ssa -----------------
|
|
|
|
// deref returns a pointer's element type; otherwise it returns typ.
|
|
func deref(typ types.Type) types.Type {
|
|
if p, ok := typ.Underlying().(*types.Pointer); ok {
|
|
return p.Elem()
|
|
}
|
|
return typ
|
|
}
|
|
|
|
func unparen(e ast.Expr) ast.Expr { return astutil.Unparen(e) }
|
|
|
|
func isInterface(T types.Type) bool { return types.IsInterface(T) }
|