674 lines
16 KiB
Go
674 lines
16 KiB
Go
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// Copyright 2011 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 main
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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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"os"
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"reflect"
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"strings"
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)
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// Partial type checker.
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//
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// The fact that it is partial is very important: the input is
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// an AST and a description of some type information to
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// assume about one or more packages, but not all the
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// packages that the program imports. The checker is
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// expected to do as much as it can with what it has been
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// given. There is not enough information supplied to do
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// a full type check, but the type checker is expected to
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// apply information that can be derived from variable
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// declarations, function and method returns, and type switches
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// as far as it can, so that the caller can still tell the types
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// of expression relevant to a particular fix.
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//
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// TODO(rsc,gri): Replace with go/typechecker.
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// Doing that could be an interesting test case for go/typechecker:
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// the constraints about working with partial information will
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// likely exercise it in interesting ways. The ideal interface would
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// be to pass typecheck a map from importpath to package API text
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// (Go source code), but for now we use data structures (TypeConfig, Type).
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//
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// The strings mostly use gofmt form.
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//
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// A Field or FieldList has as its type a comma-separated list
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// of the types of the fields. For example, the field list
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// x, y, z int
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// has type "int, int, int".
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// The prefix "type " is the type of a type.
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// For example, given
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// var x int
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// type T int
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// x's type is "int" but T's type is "type int".
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// mkType inserts the "type " prefix.
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// getType removes it.
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// isType tests for it.
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func mkType(t string) string {
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return "type " + t
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}
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func getType(t string) string {
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if !isType(t) {
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return ""
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}
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return t[len("type "):]
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}
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func isType(t string) bool {
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return strings.HasPrefix(t, "type ")
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}
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// TypeConfig describes the universe of relevant types.
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// For ease of creation, the types are all referred to by string
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// name (e.g., "reflect.Value"). TypeByName is the only place
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// where the strings are resolved.
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type TypeConfig struct {
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Type map[string]*Type
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Var map[string]string
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Func map[string]string
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}
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// typeof returns the type of the given name, which may be of
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// the form "x" or "p.X".
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func (cfg *TypeConfig) typeof(name string) string {
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if cfg.Var != nil {
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if t := cfg.Var[name]; t != "" {
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return t
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}
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}
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if cfg.Func != nil {
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if t := cfg.Func[name]; t != "" {
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return "func()" + t
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}
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}
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return ""
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}
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// Type describes the Fields and Methods of a type.
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// If the field or method cannot be found there, it is next
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// looked for in the Embed list.
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type Type struct {
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Field map[string]string // map field name to type
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Method map[string]string // map method name to comma-separated return types (should start with "func ")
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Embed []string // list of types this type embeds (for extra methods)
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Def string // definition of named type
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}
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// dot returns the type of "typ.name", making its decision
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// using the type information in cfg.
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func (typ *Type) dot(cfg *TypeConfig, name string) string {
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if typ.Field != nil {
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if t := typ.Field[name]; t != "" {
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return t
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}
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}
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if typ.Method != nil {
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if t := typ.Method[name]; t != "" {
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return t
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}
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}
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for _, e := range typ.Embed {
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etyp := cfg.Type[e]
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if etyp != nil {
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if t := etyp.dot(cfg, name); t != "" {
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return t
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}
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}
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}
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return ""
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}
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// typecheck type checks the AST f assuming the information in cfg.
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// It returns two maps with type information:
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// typeof maps AST nodes to type information in gofmt string form.
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// assign maps type strings to lists of expressions that were assigned
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// to values of another type that were assigned to that type.
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func typecheck(cfg *TypeConfig, f *ast.File) (typeof map[interface{}]string, assign map[string][]interface{}) {
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typeof = make(map[interface{}]string)
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assign = make(map[string][]interface{})
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cfg1 := &TypeConfig{}
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*cfg1 = *cfg // make copy so we can add locally
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copied := false
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// gather function declarations
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for _, decl := range f.Decls {
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fn, ok := decl.(*ast.FuncDecl)
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if !ok {
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continue
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}
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typecheck1(cfg, fn.Type, typeof, assign)
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t := typeof[fn.Type]
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if fn.Recv != nil {
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// The receiver must be a type.
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rcvr := typeof[fn.Recv]
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if !isType(rcvr) {
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if len(fn.Recv.List) != 1 {
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continue
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}
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rcvr = mkType(gofmt(fn.Recv.List[0].Type))
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typeof[fn.Recv.List[0].Type] = rcvr
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}
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rcvr = getType(rcvr)
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if rcvr != "" && rcvr[0] == '*' {
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rcvr = rcvr[1:]
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}
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typeof[rcvr+"."+fn.Name.Name] = t
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} else {
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if isType(t) {
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t = getType(t)
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} else {
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t = gofmt(fn.Type)
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}
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typeof[fn.Name] = t
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// Record typeof[fn.Name.Obj] for future references to fn.Name.
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typeof[fn.Name.Obj] = t
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}
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}
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// gather struct declarations
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for _, decl := range f.Decls {
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d, ok := decl.(*ast.GenDecl)
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if ok {
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for _, s := range d.Specs {
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switch s := s.(type) {
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case *ast.TypeSpec:
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if cfg1.Type[s.Name.Name] != nil {
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break
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}
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if !copied {
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copied = true
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// Copy map lazily: it's time.
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cfg1.Type = make(map[string]*Type)
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for k, v := range cfg.Type {
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cfg1.Type[k] = v
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}
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}
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t := &Type{Field: map[string]string{}}
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cfg1.Type[s.Name.Name] = t
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switch st := s.Type.(type) {
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case *ast.StructType:
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for _, f := range st.Fields.List {
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for _, n := range f.Names {
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t.Field[n.Name] = gofmt(f.Type)
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}
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}
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case *ast.ArrayType, *ast.StarExpr, *ast.MapType:
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t.Def = gofmt(st)
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}
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}
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}
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}
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}
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typecheck1(cfg1, f, typeof, assign)
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return typeof, assign
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}
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func makeExprList(a []*ast.Ident) []ast.Expr {
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var b []ast.Expr
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for _, x := range a {
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b = append(b, x)
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}
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return b
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}
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// Typecheck1 is the recursive form of typecheck.
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// It is like typecheck but adds to the information in typeof
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// instead of allocating a new map.
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func typecheck1(cfg *TypeConfig, f interface{}, typeof map[interface{}]string, assign map[string][]interface{}) {
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// set sets the type of n to typ.
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// If isDecl is true, n is being declared.
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set := func(n ast.Expr, typ string, isDecl bool) {
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if typeof[n] != "" || typ == "" {
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if typeof[n] != typ {
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assign[typ] = append(assign[typ], n)
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}
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return
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}
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typeof[n] = typ
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// If we obtained typ from the declaration of x
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// propagate the type to all the uses.
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// The !isDecl case is a cheat here, but it makes
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// up in some cases for not paying attention to
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// struct fields. The real type checker will be
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// more accurate so we won't need the cheat.
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if id, ok := n.(*ast.Ident); ok && id.Obj != nil && (isDecl || typeof[id.Obj] == "") {
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typeof[id.Obj] = typ
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}
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}
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// Type-check an assignment lhs = rhs.
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// If isDecl is true, this is := so we can update
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// the types of the objects that lhs refers to.
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typecheckAssign := func(lhs, rhs []ast.Expr, isDecl bool) {
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if len(lhs) > 1 && len(rhs) == 1 {
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if _, ok := rhs[0].(*ast.CallExpr); ok {
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t := split(typeof[rhs[0]])
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// Lists should have same length but may not; pair what can be paired.
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for i := 0; i < len(lhs) && i < len(t); i++ {
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set(lhs[i], t[i], isDecl)
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}
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return
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}
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}
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if len(lhs) == 1 && len(rhs) == 2 {
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// x = y, ok
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rhs = rhs[:1]
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} else if len(lhs) == 2 && len(rhs) == 1 {
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// x, ok = y
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lhs = lhs[:1]
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}
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// Match as much as we can.
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for i := 0; i < len(lhs) && i < len(rhs); i++ {
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x, y := lhs[i], rhs[i]
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if typeof[y] != "" {
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set(x, typeof[y], isDecl)
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} else {
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set(y, typeof[x], false)
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}
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}
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}
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expand := func(s string) string {
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typ := cfg.Type[s]
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if typ != nil && typ.Def != "" {
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return typ.Def
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}
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return s
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}
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// The main type check is a recursive algorithm implemented
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// by walkBeforeAfter(n, before, after).
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// Most of it is bottom-up, but in a few places we need
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// to know the type of the function we are checking.
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// The before function records that information on
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// the curfn stack.
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var curfn []*ast.FuncType
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before := func(n interface{}) {
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// push function type on stack
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switch n := n.(type) {
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case *ast.FuncDecl:
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curfn = append(curfn, n.Type)
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case *ast.FuncLit:
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curfn = append(curfn, n.Type)
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}
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}
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// After is the real type checker.
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after := func(n interface{}) {
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if n == nil {
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return
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}
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if false && reflect.TypeOf(n).Kind() == reflect.Ptr { // debugging trace
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defer func() {
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if t := typeof[n]; t != "" {
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pos := fset.Position(n.(ast.Node).Pos())
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fmt.Fprintf(os.Stderr, "%s: typeof[%s] = %s\n", pos, gofmt(n), t)
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}
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}()
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}
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switch n := n.(type) {
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case *ast.FuncDecl, *ast.FuncLit:
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// pop function type off stack
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curfn = curfn[:len(curfn)-1]
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case *ast.FuncType:
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typeof[n] = mkType(joinFunc(split(typeof[n.Params]), split(typeof[n.Results])))
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case *ast.FieldList:
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// Field list is concatenation of sub-lists.
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t := ""
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for _, field := range n.List {
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if t != "" {
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t += ", "
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}
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t += typeof[field]
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}
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typeof[n] = t
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case *ast.Field:
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// Field is one instance of the type per name.
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all := ""
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t := typeof[n.Type]
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if !isType(t) {
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// Create a type, because it is typically *T or *p.T
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// and we might care about that type.
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t = mkType(gofmt(n.Type))
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typeof[n.Type] = t
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}
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t = getType(t)
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if len(n.Names) == 0 {
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all = t
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} else {
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for _, id := range n.Names {
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if all != "" {
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all += ", "
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}
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all += t
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typeof[id.Obj] = t
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typeof[id] = t
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}
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}
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typeof[n] = all
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case *ast.ValueSpec:
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// var declaration. Use type if present.
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if n.Type != nil {
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t := typeof[n.Type]
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if !isType(t) {
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t = mkType(gofmt(n.Type))
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typeof[n.Type] = t
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}
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t = getType(t)
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for _, id := range n.Names {
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set(id, t, true)
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}
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}
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// Now treat same as assignment.
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typecheckAssign(makeExprList(n.Names), n.Values, true)
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case *ast.AssignStmt:
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typecheckAssign(n.Lhs, n.Rhs, n.Tok == token.DEFINE)
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case *ast.Ident:
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// Identifier can take its type from underlying object.
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if t := typeof[n.Obj]; t != "" {
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typeof[n] = t
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}
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case *ast.SelectorExpr:
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// Field or method.
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name := n.Sel.Name
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if t := typeof[n.X]; t != "" {
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if strings.HasPrefix(t, "*") {
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t = t[1:] // implicit *
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}
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if typ := cfg.Type[t]; typ != nil {
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if t := typ.dot(cfg, name); t != "" {
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typeof[n] = t
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return
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}
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}
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tt := typeof[t+"."+name]
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if isType(tt) {
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typeof[n] = getType(tt)
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return
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}
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}
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// Package selector.
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if x, ok := n.X.(*ast.Ident); ok && x.Obj == nil {
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str := x.Name + "." + name
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if cfg.Type[str] != nil {
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typeof[n] = mkType(str)
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return
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}
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if t := cfg.typeof(x.Name + "." + name); t != "" {
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typeof[n] = t
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return
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}
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}
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case *ast.CallExpr:
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// make(T) has type T.
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if isTopName(n.Fun, "make") && len(n.Args) >= 1 {
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typeof[n] = gofmt(n.Args[0])
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return
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}
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// new(T) has type *T
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if isTopName(n.Fun, "new") && len(n.Args) == 1 {
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typeof[n] = "*" + gofmt(n.Args[0])
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return
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}
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// Otherwise, use type of function to determine arguments.
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t := typeof[n.Fun]
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in, out := splitFunc(t)
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if in == nil && out == nil {
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return
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}
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typeof[n] = join(out)
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for i, arg := range n.Args {
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if i >= len(in) {
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break
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}
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if typeof[arg] == "" {
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typeof[arg] = in[i]
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}
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}
|
||
|
|
||
|
case *ast.TypeAssertExpr:
|
||
|
// x.(type) has type of x.
|
||
|
if n.Type == nil {
|
||
|
typeof[n] = typeof[n.X]
|
||
|
return
|
||
|
}
|
||
|
// x.(T) has type T.
|
||
|
if t := typeof[n.Type]; isType(t) {
|
||
|
typeof[n] = getType(t)
|
||
|
} else {
|
||
|
typeof[n] = gofmt(n.Type)
|
||
|
}
|
||
|
|
||
|
case *ast.SliceExpr:
|
||
|
// x[i:j] has type of x.
|
||
|
typeof[n] = typeof[n.X]
|
||
|
|
||
|
case *ast.IndexExpr:
|
||
|
// x[i] has key type of x's type.
|
||
|
t := expand(typeof[n.X])
|
||
|
if strings.HasPrefix(t, "[") || strings.HasPrefix(t, "map[") {
|
||
|
// Lazy: assume there are no nested [] in the array
|
||
|
// length or map key type.
|
||
|
if i := strings.Index(t, "]"); i >= 0 {
|
||
|
typeof[n] = t[i+1:]
|
||
|
}
|
||
|
}
|
||
|
|
||
|
case *ast.StarExpr:
|
||
|
// *x for x of type *T has type T when x is an expr.
|
||
|
// We don't use the result when *x is a type, but
|
||
|
// compute it anyway.
|
||
|
t := expand(typeof[n.X])
|
||
|
if isType(t) {
|
||
|
typeof[n] = "type *" + getType(t)
|
||
|
} else if strings.HasPrefix(t, "*") {
|
||
|
typeof[n] = t[len("*"):]
|
||
|
}
|
||
|
|
||
|
case *ast.UnaryExpr:
|
||
|
// &x for x of type T has type *T.
|
||
|
t := typeof[n.X]
|
||
|
if t != "" && n.Op == token.AND {
|
||
|
typeof[n] = "*" + t
|
||
|
}
|
||
|
|
||
|
case *ast.CompositeLit:
|
||
|
// T{...} has type T.
|
||
|
typeof[n] = gofmt(n.Type)
|
||
|
|
||
|
case *ast.ParenExpr:
|
||
|
// (x) has type of x.
|
||
|
typeof[n] = typeof[n.X]
|
||
|
|
||
|
case *ast.RangeStmt:
|
||
|
t := expand(typeof[n.X])
|
||
|
if t == "" {
|
||
|
return
|
||
|
}
|
||
|
var key, value string
|
||
|
if t == "string" {
|
||
|
key, value = "int", "rune"
|
||
|
} else if strings.HasPrefix(t, "[") {
|
||
|
key = "int"
|
||
|
if i := strings.Index(t, "]"); i >= 0 {
|
||
|
value = t[i+1:]
|
||
|
}
|
||
|
} else if strings.HasPrefix(t, "map[") {
|
||
|
if i := strings.Index(t, "]"); i >= 0 {
|
||
|
key, value = t[4:i], t[i+1:]
|
||
|
}
|
||
|
}
|
||
|
changed := false
|
||
|
if n.Key != nil && key != "" {
|
||
|
changed = true
|
||
|
set(n.Key, key, n.Tok == token.DEFINE)
|
||
|
}
|
||
|
if n.Value != nil && value != "" {
|
||
|
changed = true
|
||
|
set(n.Value, value, n.Tok == token.DEFINE)
|
||
|
}
|
||
|
// Ugly failure of vision: already type-checked body.
|
||
|
// Do it again now that we have that type info.
|
||
|
if changed {
|
||
|
typecheck1(cfg, n.Body, typeof, assign)
|
||
|
}
|
||
|
|
||
|
case *ast.TypeSwitchStmt:
|
||
|
// Type of variable changes for each case in type switch,
|
||
|
// but go/parser generates just one variable.
|
||
|
// Repeat type check for each case with more precise
|
||
|
// type information.
|
||
|
as, ok := n.Assign.(*ast.AssignStmt)
|
||
|
if !ok {
|
||
|
return
|
||
|
}
|
||
|
varx, ok := as.Lhs[0].(*ast.Ident)
|
||
|
if !ok {
|
||
|
return
|
||
|
}
|
||
|
t := typeof[varx]
|
||
|
for _, cas := range n.Body.List {
|
||
|
cas := cas.(*ast.CaseClause)
|
||
|
if len(cas.List) == 1 {
|
||
|
// Variable has specific type only when there is
|
||
|
// exactly one type in the case list.
|
||
|
if tt := typeof[cas.List[0]]; isType(tt) {
|
||
|
tt = getType(tt)
|
||
|
typeof[varx] = tt
|
||
|
typeof[varx.Obj] = tt
|
||
|
typecheck1(cfg, cas.Body, typeof, assign)
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
// Restore t.
|
||
|
typeof[varx] = t
|
||
|
typeof[varx.Obj] = t
|
||
|
|
||
|
case *ast.ReturnStmt:
|
||
|
if len(curfn) == 0 {
|
||
|
// Probably can't happen.
|
||
|
return
|
||
|
}
|
||
|
f := curfn[len(curfn)-1]
|
||
|
res := n.Results
|
||
|
if f.Results != nil {
|
||
|
t := split(typeof[f.Results])
|
||
|
for i := 0; i < len(res) && i < len(t); i++ {
|
||
|
set(res[i], t[i], false)
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
walkBeforeAfter(f, before, after)
|
||
|
}
|
||
|
|
||
|
// Convert between function type strings and lists of types.
|
||
|
// Using strings makes this a little harder, but it makes
|
||
|
// a lot of the rest of the code easier. This will all go away
|
||
|
// when we can use go/typechecker directly.
|
||
|
|
||
|
// splitFunc splits "func(x,y,z) (a,b,c)" into ["x", "y", "z"] and ["a", "b", "c"].
|
||
|
func splitFunc(s string) (in, out []string) {
|
||
|
if !strings.HasPrefix(s, "func(") {
|
||
|
return nil, nil
|
||
|
}
|
||
|
|
||
|
i := len("func(") // index of beginning of 'in' arguments
|
||
|
nparen := 0
|
||
|
for j := i; j < len(s); j++ {
|
||
|
switch s[j] {
|
||
|
case '(':
|
||
|
nparen++
|
||
|
case ')':
|
||
|
nparen--
|
||
|
if nparen < 0 {
|
||
|
// found end of parameter list
|
||
|
out := strings.TrimSpace(s[j+1:])
|
||
|
if len(out) >= 2 && out[0] == '(' && out[len(out)-1] == ')' {
|
||
|
out = out[1 : len(out)-1]
|
||
|
}
|
||
|
return split(s[i:j]), split(out)
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
return nil, nil
|
||
|
}
|
||
|
|
||
|
// joinFunc is the inverse of splitFunc.
|
||
|
func joinFunc(in, out []string) string {
|
||
|
outs := ""
|
||
|
if len(out) == 1 {
|
||
|
outs = " " + out[0]
|
||
|
} else if len(out) > 1 {
|
||
|
outs = " (" + join(out) + ")"
|
||
|
}
|
||
|
return "func(" + join(in) + ")" + outs
|
||
|
}
|
||
|
|
||
|
// split splits "int, float" into ["int", "float"] and splits "" into [].
|
||
|
func split(s string) []string {
|
||
|
out := []string{}
|
||
|
i := 0 // current type being scanned is s[i:j].
|
||
|
nparen := 0
|
||
|
for j := 0; j < len(s); j++ {
|
||
|
switch s[j] {
|
||
|
case ' ':
|
||
|
if i == j {
|
||
|
i++
|
||
|
}
|
||
|
case '(':
|
||
|
nparen++
|
||
|
case ')':
|
||
|
nparen--
|
||
|
if nparen < 0 {
|
||
|
// probably can't happen
|
||
|
return nil
|
||
|
}
|
||
|
case ',':
|
||
|
if nparen == 0 {
|
||
|
if i < j {
|
||
|
out = append(out, s[i:j])
|
||
|
}
|
||
|
i = j + 1
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
if nparen != 0 {
|
||
|
// probably can't happen
|
||
|
return nil
|
||
|
}
|
||
|
if i < len(s) {
|
||
|
out = append(out, s[i:])
|
||
|
}
|
||
|
return out
|
||
|
}
|
||
|
|
||
|
// join is the inverse of split.
|
||
|
func join(x []string) string {
|
||
|
return strings.Join(x, ", ")
|
||
|
}
|