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go/types: allow embedding overlapping interfaces

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Quietly drop duplicate methods from embedded interfaces
if they have an identical signature to existing methods.

Instead of adjusting the prior syntax-based only method set
computation where methods don't have signature information
(and thus where de-duplication according to the new rules
would have been somewhat tricky to get right), this change
completely rewrites interface method set computation, taking
a page from the cmd/compiler's implementation. In a first
pass, when type-checking interfaces, explicit methods and
embedded interfaces are collected, but the interfaces are
not "expanded", that is the final method set computation
is done lazily, either when needed for method lookup, or
at the end of type-checking.

While this is a substantial rewrite, it allows us to get
rid of the separate (duplicate and delicate) syntactical
method set computation and generally simplifies checking
of interface types significantly. A few (esoteric) test
cases now have slightly different error messages but all
tests that are accepted by cmd/compile are also accepted
by go/types.

(This is a replacement for golang.org/cl/190258.)

Updates #6977.

Change-Id: Ic8b9321374ab4f617498d97c12871b69d1119735
Reviewed-on: https://go-review.googlesource.com/c/go/+/191257
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Robert Griesemer 2019-08-21 17:13:45 -07:00
parent 89f02eb837
commit a80c5f0588
15 changed files with 294 additions and 689 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/go/types/builtins.go
View File

@ -559,7 +559,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
base := derefStructPtr(x.typ)
sel := selx.Sel.Name
obj, index, indirect := LookupFieldOrMethod(base, false, check.pkg, sel)
obj, index, indirect := check.LookupFieldOrMethod(base, false, check.pkg, sel)
switch obj.(type) {
case nil:
check.invalidArg(x.pos(), "%s has no single field %s", base, sel)

6
src/go/types/call.go
View File

@ -370,7 +370,7 @@ func (check *Checker) selector(x *operand, e *ast.SelectorExpr) {
goto Error
}
obj, index, indirect = LookupFieldOrMethod(x.typ, x.mode == variable, check.pkg, sel)
obj, index, indirect = check.LookupFieldOrMethod(x.typ, x.mode == variable, check.pkg, sel)
if obj == nil {
switch {
case index != nil:
@ -437,6 +437,10 @@ func (check *Checker) selector(x *operand, e *ast.SelectorExpr) {
if debug {
// Verify that LookupFieldOrMethod and MethodSet.Lookup agree.
// TODO(gri) This only works because we call LookupFieldOrMethod
// _before_ calling NewMethodSet: LookupFieldOrMethod completes
// any incomplete interfaces so they are avaible to NewMethodSet
// (which assumes that interfaces have been completed already).
typ := x.typ
if x.mode == variable {
// If typ is not an (unnamed) pointer or an interface,

25
src/go/types/check.go
View File

@ -76,8 +76,9 @@ type Checker struct {
fset *token.FileSet
pkg *Package
*Info
objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
posMap map[*Interface][]token.Pos // maps interface types to lists of embedded interface positions
// information collected during type-checking of a set of package files
// (initialized by Files, valid only for the duration of check.Files;
@ -86,12 +87,10 @@ type Checker struct {
unusedDotImports map[*Scope]map[*Package]token.Pos // positions of unused dot-imported packages for each file scope
firstErr error // first error encountered
methods map[*TypeName][]*Func // maps package scope type names to associated non-blank, non-interface methods
// TODO(gri) move interfaces up to the group of fields persistent across check.Files invocations (see also comment in Checker.initFiles)
interfaces map[*TypeName]*ifaceInfo // maps interface type names to corresponding interface infos
untyped map[ast.Expr]exprInfo // map of expressions without final type
delayed []func() // stack of delayed actions
objPath []Object // path of object dependencies during type inference (for cycle reporting)
methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
untyped map[ast.Expr]exprInfo // map of expressions without final type
delayed []func() // stack of delayed actions
objPath []Object // path of object dependencies during type inference (for cycle reporting)
// context within which the current object is type-checked
// (valid only for the duration of type-checking a specific object)
@ -181,6 +180,7 @@ func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Ch
Info: info,
objMap: make(map[Object]*declInfo),
impMap: make(map[importKey]*Package),
posMap: make(map[*Interface][]token.Pos),
}
}
@ -193,15 +193,6 @@ func (check *Checker) initFiles(files []*ast.File) {
check.firstErr = nil
check.methods = nil
// Don't clear the interfaces cache! It's important that we don't recompute
// ifaceInfos repeatedly (due to multiple check.Files calls) because when
// they are recomputed, they are not used in the context of their original
// declaration (because those types are already type-checked, typically) and
// then they will get the wrong receiver types, which matters for go/types
// clients. It is also safe to not reset the interfaces cache because files
// added to a package cannot change (add methods to) existing interface types;
// they can only add new interfaces. See also the respective comment in
// checker.infoFromTypeName (interfaces.go). Was bug - see issue #29029.
check.untyped = nil
check.delayed = nil

1
src/go/types/check_test.go
View File

@ -97,6 +97,7 @@ var tests = [][]string{
{"testdata/issue23203a.src"},
{"testdata/issue23203b.src"},
{"testdata/issue28251.src"},
{"testdata/issue6977.src"},
}
var fset = token.NewFileSet()

4
src/go/types/errors.go
View File

@ -82,6 +82,10 @@ func (check *Checker) err(pos token.Pos, msg string, soft bool) {
check.firstErr = err
}
if trace {
check.trace(pos, "ERROR: %s", msg)
}
f := check.conf.Error
if f == nil {
panic(bailout{}) // report only first error

451
src/go/types/interfaces.go
View File

@ -1,451 +0,0 @@
// Copyright 2017 The Go Authors. All rights reserved.
// Use of this src code is governed by a BSD-style
// license that can be found in the LICENSE file.
package types
import (
"bytes"
"fmt"
"go/ast"
"go/token"
)
// This file implements the collection of an interface's methods
// without relying on partially computed types of methods or interfaces
// for interface types declared at the package level.
//
// Because interfaces must not embed themselves, directly or indirectly,
// the method set of a valid interface can always be computed independent
// of any cycles that might exist via method signatures (see also issue #18395).
//
// Except for blank method name and interface cycle errors, no errors
// are reported. Affected methods or embedded interfaces are silently
// dropped. Subsequent type-checking of the interface will check
// signatures and embedded interfaces and report errors at that time.
//
// Only infoFromTypeLit should be called directly from code outside this file
// to compute an ifaceInfo.
// ifaceInfo describes the method set for an interface.
// The zero value for an ifaceInfo is a ready-to-use ifaceInfo representing
// the empty interface.
type ifaceInfo struct {
explicits int // number of explicitly declared methods
methods []*methodInfo // all methods, starting with explicitly declared ones in source order
}
// emptyIfaceInfo represents the ifaceInfo for the empty interface.
var emptyIfaceInfo ifaceInfo
func (info *ifaceInfo) String() string {
var buf bytes.Buffer
fmt.Fprintf(&buf, "interface{")
for i, m := range info.methods {
if i > 0 {
fmt.Fprint(&buf, " ")
}
fmt.Fprint(&buf, m)
}
fmt.Fprintf(&buf, "}")
return buf.String()
}
// methodInfo represents an interface method.
// At least one of src or fun must be non-nil.
// (Methods declared in the current package have a non-nil scope
// and src, and eventually a non-nil fun field; imported and pre-
// declared methods have a nil scope and src, and only a non-nil
// fun field.)
type methodInfo struct {
scope *Scope // scope of interface method; or nil
src *ast.Field // syntax tree representation of interface method; or nil
fun *Func // corresponding fully type-checked method type; or nil
}
func (info *methodInfo) String() string {
if info.fun != nil {
return info.fun.name
}
return info.src.Names[0].Name
}
func (info *methodInfo) Pos() token.Pos {
if info.fun != nil {
return info.fun.Pos()
}
return info.src.Pos()
}
func (info *methodInfo) id(pkg *Package) string {
if info.fun != nil {
return info.fun.Id()
}
return Id(pkg, info.src.Names[0].Name)
}
// A methodInfoSet maps method ids to methodInfos.
// It is used to determine duplicate declarations.
// (A methodInfo set is the equivalent of an objset
// but for methodInfos rather than Objects.)
type methodInfoSet map[string]*methodInfo
// insert attempts to insert an method m into the method set s.
// If s already contains an alternative method alt with
// the same name, insert leaves s unchanged and returns alt.
// Otherwise it inserts m and returns nil.
func (s *methodInfoSet) insert(pkg *Package, m *methodInfo) *methodInfo {
id := m.id(pkg)
if alt := (*s)[id]; alt != nil {
return alt
}
if *s == nil {
*s = make(methodInfoSet)
}
(*s)[id] = m
return nil
}
// like Checker.declareInSet but for method infos.
func (check *Checker) declareInMethodSet(mset *methodInfoSet, pos token.Pos, m *methodInfo) bool {
if alt := mset.insert(check.pkg, m); alt != nil {
check.errorf(pos, "%s redeclared", m)
check.reportAltMethod(alt)
return false
}
return true
}
// like Checker.reportAltDecl but for method infos.
func (check *Checker) reportAltMethod(m *methodInfo) {
if pos := m.Pos(); pos.IsValid() {
// We use "other" rather than "previous" here because
// the first declaration seen may not be textually
// earlier in the source.
check.errorf(pos, "\tother declaration of %s", m) // secondary error, \t indented
}
}
// infoFromTypeLit computes the method set for the given interface iface
// declared in scope.
// If a corresponding type name exists (tname != nil), it is used for
// cycle detection and to cache the method set.
// The result is the method set, or nil if there is a cycle via embedded
// interfaces. A non-nil result doesn't mean that there were no errors,
// but they were either reported (e.g., blank methods), or will be found
// (again) when computing the interface's type.
// If tname is not nil it must be the last element in path.
func (check *Checker) infoFromTypeLit(scope *Scope, iface *ast.InterfaceType, tname *TypeName, path []*TypeName) (info *ifaceInfo) {
assert(iface != nil)
// lazy-allocate interfaces map
if check.interfaces == nil {
check.interfaces = make(map[*TypeName]*ifaceInfo)
}
if trace {
check.trace(iface.Pos(), "-- collect methods for %v (path = %s, objPath = %s)", iface, pathString(path), objPathString(check.objPath))
check.indent++
defer func() {
check.indent--
check.trace(iface.Pos(), "=> %s", info)
}()
}
// If the interface is named, check if we computed info already.
//
// This is not simply an optimization; we may run into stack
// overflow with recursive interface declarations. Example:
//
// type T interface {
// m() interface { T }
// }
//
// (Since recursive definitions can only be expressed via names,
// it is sufficient to track named interfaces here.)
//
// While at it, use the same mechanism to detect cycles. (We still
// have the path-based cycle check because we want to report the
// entire cycle if present.)
if tname != nil {
assert(path[len(path)-1] == tname) // tname must be last path element
var found bool
if info, found = check.interfaces[tname]; found {
if info == nil {
// We have a cycle and use check.cycle to report it.
// We are guaranteed that check.cycle also finds the
// cycle because when infoFromTypeLit is called, any
// tname that's already in check.interfaces was also
// added to the path. (But the converse is not true:
// A non-nil tname is always the last element in path.)
ok := check.cycle(tname, path, true)
assert(ok)
}
return
}
check.interfaces[tname] = nil // computation started but not complete
}
if iface.Methods.List == nil {
// fast track for empty interface
info = &emptyIfaceInfo
} else {
// (syntactically) non-empty interface
info = new(ifaceInfo)
// collect explicitly declared methods and embedded interfaces
var mset methodInfoSet
var embeddeds []*ifaceInfo
var positions []token.Pos // entries correspond to positions of embeddeds; used for error reporting
for _, f := range iface.Methods.List {
if len(f.Names) > 0 {
// We have a method with name f.Names[0].
// (The parser ensures that there's only one method
// and we don't care if a constructed AST has more.)
// spec: "As with all method sets, in an interface type,
// each method must have a unique non-blank name."
if name := f.Names[0]; name.Name == "_" {
check.errorf(name.Pos(), "invalid method name _")
continue // ignore
}
m := &methodInfo{scope: scope, src: f}
if check.declareInMethodSet(&mset, f.Pos(), m) {
info.methods = append(info.methods, m)
}
} else {
// We have an embedded interface and f.Type is its
// (possibly qualified) embedded type name. Collect
// it if it's a valid interface.
var e *ifaceInfo
switch ename := f.Type.(type) {
case *ast.Ident:
e = check.infoFromTypeName(scope, ename, path)
case *ast.SelectorExpr:
e = check.infoFromQualifiedTypeName(scope, ename)
default:
// The parser makes sure we only see one of the above.
// Constructed ASTs may contain other (invalid) nodes;
// we simply ignore them. The full type-checking pass
// will report those as errors later.
}
if e != nil {
embeddeds = append(embeddeds, e)
positions = append(positions, f.Type.Pos())
}
}
}
info.explicits = len(info.methods)
// collect methods of embedded interfaces
for i, e := range embeddeds {
pos := positions[i] // position of type name of embedded interface
for _, m := range e.methods {
if check.declareInMethodSet(&mset, pos, m) {
info.methods = append(info.methods, m)
}
}
}
}
// mark check.interfaces as complete
assert(info != nil)
if tname != nil {
check.interfaces[tname] = info
}
return
}
// infoFromTypeName computes the method set for the given type name
// which must denote a type whose underlying type is an interface.
// The same result qualifications apply as for infoFromTypeLit.
// infoFromTypeName should only be called from infoFromTypeLit.
func (check *Checker) infoFromTypeName(scope *Scope, name *ast.Ident, path []*TypeName) *ifaceInfo {
// A single call of infoFromTypeName handles a sequence of (possibly
// recursive) type declarations connected via unqualified type names.
// Each type declaration leading to another typename causes a "tail call"
// (goto) of this function. The general scenario looks like this:
//
// ...
// type Pn T // previous declarations leading to T, path = [..., Pn]
// type T interface { T0; ... } // T0 leads to call of infoFromTypeName
//
// // infoFromTypeName(name = T0, path = [..., Pn, T])
// type T0 T1 // path = [..., Pn, T, T0]
// type T1 T2 <-+ // path = [..., Pn, T, T0, T1]
// type T2 ... | // path = [..., Pn, T, T0, T1, T2]
// type Tn T1 --+ // path = [..., Pn, T, T0, T1, T2, Tn] and T1 is in path => cycle
//
// infoFromTypeName returns nil when such a cycle is detected. But in
// contrast to cycles involving interfaces, we must not report the
// error for "type name only" cycles because they will be found again
// during type-checking of embedded interfaces. Reporting those cycles
// here would lead to double reporting. Cycles involving embedding are
// not reported again later because type-checking of interfaces relies
// on the ifaceInfos computed here which are cycle-free by design.
//
// Remember the path length to detect "type name only" cycles.
start := len(path)
typenameLoop:
// name must be a type name denoting a type whose underlying type is an interface
_, obj := scope.LookupParent(name.Name, check.pos)
if obj == nil {
return nil
}
tname, _ := obj.(*TypeName)
if tname == nil {
return nil
}
// We have a type name. It may be predeclared (error type),
// imported (dot import), or declared by a type declaration.
// It may not be an interface (e.g., predeclared type int).
// Resolve it by analyzing each possible case.
// Abort but don't report an error if we have a "type name only"
// cycle (see big function comment).
if check.cycle(tname, path[start:], false) {
return nil
}
// Abort and report an error if we have a general cycle.
if check.cycle(tname, path, true) {
return nil
}
path = append(path, tname)
// If tname is a package-level type declaration, it must be
// in the objMap. Follow the RHS of that declaration if so.
// The RHS may be a literal type (likely case), or another
// (possibly parenthesized and/or qualified) type name.
// (The declaration may be an alias declaration, but it
// doesn't matter for the purpose of determining the under-
// lying interface.)
if decl := check.objMap[tname]; decl != nil {
switch typ := unparen(decl.typ).(type) {
case *ast.Ident:
// type tname T
name = typ
goto typenameLoop
case *ast.SelectorExpr:
// type tname p.T
return check.infoFromQualifiedTypeName(decl.file, typ)
case *ast.InterfaceType:
// type tname interface{...}
// If tname is fully type-checked at this point (tname.color() == black)
// we could use infoFromType here. But in this case, the interface must
// be in the check.interfaces cache as well, which will be hit when we
// call infoFromTypeLit below, and which will be faster. It is important
// that we use that previously computed interface because its methods
// have the correct receiver type (for go/types clients). Thus, the
// check.interfaces cache must be up-to-date across even across multiple
// check.Files calls (was bug - see issue #29029).
return check.infoFromTypeLit(decl.file, typ, tname, path)
}
// type tname X // and X is not an interface type
return nil
}
// If tname is not a package-level declaration, in a well-typed
// program it should be a predeclared (error type), imported (dot
// import), or function local declaration. Either way, it should
// have been fully declared before use, except if there is a direct
// cycle, and direct cycles will be caught above. Also, the denoted
// type should be an interface (e.g., int is not an interface).
if typ := tname.typ; typ != nil {
// typ should be an interface
if ityp, _ := typ.Underlying().(*Interface); ityp != nil {
return infoFromType(ityp)
}
}
// In all other cases we have some error.
return nil
}
// infoFromQualifiedTypeName computes the method set for the given qualified type name, or nil.
func (check *Checker) infoFromQualifiedTypeName(scope *Scope, qname *ast.SelectorExpr) *ifaceInfo {
// see also Checker.selector
name, _ := qname.X.(*ast.Ident)
if name == nil {
return nil
}
_, obj1 := scope.LookupParent(name.Name, check.pos)
if obj1 == nil {
return nil
}
pname, _ := obj1.(*PkgName)
if pname == nil {
return nil
}
assert(pname.pkg == check.pkg)
obj2 := pname.imported.scope.Lookup(qname.Sel.Name)
if obj2 == nil || !obj2.Exported() {
return nil
}
tname, _ := obj2.(*TypeName)
if tname == nil {
return nil
}
ityp, _ := tname.typ.Underlying().(*Interface)
if ityp == nil {
return nil
}
return infoFromType(ityp)
}
// infoFromType computes the method set for the given interface type.
// The result is never nil.
func infoFromType(typ *Interface) *ifaceInfo {
assert(typ.allMethods != nil) // typ must be completely set up
// fast track for empty interface
n := len(typ.allMethods)
if n == 0 {
return &emptyIfaceInfo
}
info := new(ifaceInfo)
info.explicits = len(typ.methods)
info.methods = make([]*methodInfo, n)
// If there are no embedded interfaces, simply collect the
// explicitly declared methods (optimization of common case).
if len(typ.methods) == n {
for i, m := range typ.methods {
info.methods[i] = &methodInfo{fun: m}
}
return info
}
// Interface types have a separate list for explicitly declared methods
// which shares its methods with the list of all (explicitly declared or
// embedded) methods. Collect all methods in a set so we can separate
// the embedded methods from the explicitly declared ones.
all := make(map[*Func]bool, n)
for _, m := range typ.allMethods {
all[m] = true
}
assert(len(all) == n) // methods must be unique
// collect explicitly declared methods
info.methods = make([]*methodInfo, n)
for i, m := range typ.methods {
info.methods[i] = &methodInfo{fun: m}
delete(all, m)
}
// collect remaining (embedded) methods
i := len(typ.methods)
for m := range all {
info.methods[i] = &methodInfo{fun: m}
i++
}
assert(i == n)
return info
}

31
src/go/types/lookup.go
View File

@ -6,11 +6,6 @@
package types
// Internal use of LookupFieldOrMethod: If the obj result is a method
// associated with a concrete (non-interface) type, the method's signature
// may not be fully set up. Call Checker.objDecl(obj, nil) before accessing
// the method's type.
// LookupFieldOrMethod looks up a field or method with given package and name
// in T and returns the corresponding *Var or *Func, an index sequence, and a
// bool indicating if there were any pointer indirections on the path to the
@ -38,6 +33,19 @@ package types
// the method's formal receiver base type, nor was the receiver addressable.
//
func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (obj Object, index []int, indirect bool) {
return (*Checker)(nil).LookupFieldOrMethod(T, addressable, pkg, name)
}
// Internal use of Checker.LookupFieldOrMethod: If the obj result is a method
// associated with a concrete (non-interface) type, the method's signature
// may not be fully set up. Call Checker.objDecl(obj, nil) before accessing
// the method's type.
// TODO(gri) Now that we provide the *Checker, we can probably remove this
// caveat by calling Checker.objDecl from LookupFieldOrMethod. Investigate.
// LookupFieldOrMethod is like the external version but completes interfaces
// as necessary.
func (check *Checker) LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (obj Object, index []int, indirect bool) {
// Methods cannot be associated to a named pointer type
// (spec: "The type denoted by T is called the receiver base type;
// it must not be a pointer or interface type and it must be declared
@ -47,7 +55,7 @@ func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
// not have found it for T (see also issue 8590).
if t, _ := T.(*Named); t != nil {
if p, _ := t.underlying.(*Pointer); p != nil {
obj, index, indirect = lookupFieldOrMethod(p, false, pkg, name)
obj, index, indirect = check.lookupFieldOrMethod(p, false, pkg, name)
if _, ok := obj.(*Func); ok {
return nil, nil, false
}
@ -55,7 +63,7 @@ func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
}
}
return lookupFieldOrMethod(T, addressable, pkg, name)
return check.lookupFieldOrMethod(T, addressable, pkg, name)
}
// TODO(gri) The named type consolidation and seen maps below must be
@ -63,7 +71,8 @@ func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
// types always have only one representation (even when imported
// indirectly via different packages.)
func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (obj Object, index []int, indirect bool) {
// lookupFieldOrMethod should only be called by LookupFieldOrMethod and missingMethod.
func (check *Checker) lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (obj Object, index []int, indirect bool) {
// WARNING: The code in this function is extremely subtle - do not modify casually!
// This function and NewMethodSet should be kept in sync.
@ -166,6 +175,7 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
case *Interface:
// look for a matching method
// TODO(gri) t.allMethods is sorted - use binary search
check.completeInterface(t)
if i, m := lookupMethod(t.allMethods, pkg, name); m != nil {
assert(m.typ != nil)
index = concat(e.index, i)
@ -261,6 +271,8 @@ func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType b
// an exported API call (such as MissingMethod), i.e., when all
// methods have been type-checked.
func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
check.completeInterface(T)
// fast path for common case
if T.Empty() {
return
@ -269,6 +281,7 @@ func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method *
// TODO(gri) Consider using method sets here. Might be more efficient.
if ityp, _ := V.Underlying().(*Interface); ityp != nil {
check.completeInterface(ityp)
// TODO(gri) allMethods is sorted - can do this more efficiently
for _, m := range T.allMethods {
_, obj := lookupMethod(ityp.allMethods, m.pkg, m.name)
@ -286,7 +299,7 @@ func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method *
// A concrete type implements T if it implements all methods of T.
for _, m := range T.allMethods {
obj, _, _ := lookupFieldOrMethod(V, false, m.pkg, m.name)
obj, _, _ := check.lookupFieldOrMethod(V, false, m.pkg, m.name)
// we must have a method (not a field of matching function type)
f, _ := obj.(*Func)

5
src/go/types/methodset.go
View File

@ -62,6 +62,11 @@ func (s *MethodSet) Lookup(pkg *Package, name string) *Selection {
// Shared empty method set.
var emptyMethodSet MethodSet
// Note: NewMethodSet is intended for external use only as it
// requires interfaces to be complete. If may be used
// internally if LookupFieldOrMethod completed the same
// interfaces beforehand.
// NewMethodSet returns the method set for the given type T.
// It always returns a non-nil method set, even if it is empty.
func NewMethodSet(T Type) *MethodSet {

16
src/go/types/testdata/cycles2.src vendored
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@ -22,13 +22,13 @@ func _() {
t.f(t)
t.f(u)
u.f(t)
u.f(u)
}
// Test case for issue 6589.
// Test case for issues #6589, #33656.
type A interface {
a() interface {
@ -45,26 +45,28 @@ type B interface {
type AB interface {
a() interface {
A
B /* ERROR a redeclared */
// TODO(gri) there shouldn't be an error here. See issue #33656.
B // ERROR duplicate method a
}
b() interface {
A
B /* ERROR a redeclared */
// TODO(gri) there shouldn't be an error here. See issue #33656.
B // ERROR duplicate method a
}
}
var x AB
var y interface {
A
B /* ERROR a redeclared */
B
}
var _ = x /* ERROR cannot compare */ == y
var _ = x == y
// Test case for issue 6638.
type T interface {
m() [T /* ERROR no value */ (nil).m()[0]]int
m() [T(nil).m /* ERROR undefined */ ()[0]]int
}
// Variations of this test case.

2
src/go/types/testdata/decls0.src vendored
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@ -139,7 +139,7 @@ type (
}
I3 interface {
m1()
m1 /* ERROR "redeclared" */ ()
m1 /* ERROR "duplicate method" */ ()
}
I4 interface {
m1(x, y, x /* ERROR "redeclared" */ float32)

82
src/go/types/testdata/issue6977.src vendored Normal file
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@ -0,0 +1,82 @@
// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package p
import "io"
// Alan's initial report.
type I interface { f(); String() string }
type J interface { g(); String() string }
type IJ1 = interface { I; J }
type IJ2 = interface { f(); g(); String() string }
var _ = (*IJ1)(nil) == (*IJ2)(nil) // static assert that IJ1 and IJ2 are identical types
// The canonical example.
type ReadWriteCloser interface { io.ReadCloser; io.WriteCloser }
// Some more cases.
type M interface { m() }
type M32 interface { m() int32 }
type M64 interface { m() int64 }
type U1 interface { m() }
type U2 interface { m(); M }
type U3 interface { M; m() }
type U4 interface { M; M; M }
type U5 interface { U1; U2; U3; U4 }
type U6 interface { m(); m /* ERROR duplicate method */ () }
type U7 interface { M32 /* ERROR duplicate method */ ; m() }
type U8 interface { m(); M32 /* ERROR duplicate method */ }
type U9 interface { M32; M64 /* ERROR duplicate method */ }
// Verify that repeated embedding of the same interface(s)
// eliminates duplicate methods early (rather than at the
// end) to prevent exponential memory and time use.
// Without early elimination, computing T29 may take dozens
// of minutes.
type (
T0 interface { m() }
T1 interface { T0; T0 }
T2 interface { T1; T1 }
T3 interface { T2; T2 }
T4 interface { T3; T3 }
T5 interface { T4; T4 }
T6 interface { T5; T5 }
T7 interface { T6; T6 }
T8 interface { T7; T7 }
T9 interface { T8; T8 }
T10 interface { T9; T9 }
T11 interface { T10; T10 }
T12 interface { T11; T11 }
T13 interface { T12; T12 }
T14 interface { T13; T13 }
T15 interface { T14; T14 }
T16 interface { T15; T15 }
T17 interface { T16; T16 }
T18 interface { T17; T17 }
T19 interface { T18; T18 }
T20 interface { T19; T19 }
T21 interface { T20; T20 }
T22 interface { T21; T21 }
T23 interface { T22; T22 }
T24 interface { T23; T23 }
T25 interface { T24; T24 }
T26 interface { T25; T25 }
T27 interface { T26; T26 }
T28 interface { T27; T27 }
T29 interface { T28; T28 }
)
// Verify that m is present.
var x T29
var _ = x.m

9
src/go/types/testdata/issues.src vendored
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@ -91,7 +91,7 @@ func issue10979() {
nosuchpkg /* ERROR undeclared name: nosuchpkg */ .Nosuchtype
}
type I interface {
I /* ERROR I\.m \(value of type func\(I\)\) is not a type */ .m
I.m /* ERROR no field or method m */
m()
}
}
@ -259,10 +259,9 @@ type E = interface {
m()
}
// Test case from issue. Eventually we may disallow this due
// to the cycle via the alias type name. But for now we make
// sure this is accepted.
type issue25301b = interface {
// Test case from issue.
// cmd/compile reports a cycle as well.
type issue25301b /* ERROR cycle */ = interface {
m() interface{ issue25301b }
}

75
src/go/types/type.go
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@ -284,31 +284,27 @@ func NewInterfaceType(methods []*Func, embeddeds []Type) *Interface {
return typ
}
var mset objset
// set method receivers if necessary
for _, m := range methods {
if mset.insert(m) != nil {
panic("multiple methods with the same name")
}
// set receiver if we don't have one
if sig := m.typ.(*Signature); sig.recv == nil {
sig.recv = NewVar(m.pos, m.pkg, "", typ)
}
}
sort.Sort(byUniqueMethodName(methods))
if len(embeddeds) > 0 {
// All embedded types should be interfaces; however, defined types
// may not yet be fully resolved. Only verify that non-defined types
// are interfaces. This matches the behavior of the code before the
// fix for #25301 (issue #25596).
for _, t := range embeddeds {
if _, ok := t.(*Named); !ok && !IsInterface(t) {
panic("embedded type is not an interface")
}
// All embedded types should be interfaces; however, defined types
// may not yet be fully resolved. Only verify that non-defined types
// are interfaces. This matches the behavior of the code before the
// fix for #25301 (issue #25596).
for _, t := range embeddeds {
if _, ok := t.(*Named); !ok && !IsInterface(t) {
panic("embedded type is not an interface")
}
sort.Stable(byUniqueTypeName(embeddeds))
}
// sort for API stability
sort.Sort(byUniqueMethodName(methods))
sort.Stable(byUniqueTypeName(embeddeds))
typ.methods = methods
typ.embeddeds = embeddeds
return typ
@ -346,28 +342,45 @@ func (t *Interface) Empty() bool { return len(t.allMethods) == 0 }
// Complete computes the interface's method set. It must be called by users of
// NewInterfaceType and NewInterface after the interface's embedded types are
// fully defined and before using the interface type in any way other than to
// form other types. Complete returns the receiver.
// form other types. The interface must not contain duplicate methods or a
// panic occurs. Complete returns the receiver.
func (t *Interface) Complete() *Interface {
// TODO(gri) consolidate this method with Checker.completeInterface
if t.allMethods != nil {
return t
}
// collect all methods
var allMethods []*Func
allMethods = append(allMethods, t.methods...)
for _, et := range t.embeddeds {
it := et.Underlying().(*Interface)
it.Complete()
// copy embedded methods unchanged (see issue #28282)
allMethods = append(allMethods, it.allMethods...)
}
sort.Sort(byUniqueMethodName(allMethods))
t.allMethods = markComplete // avoid infinite recursion
// t.methods and/or t.embeddeds may have been empty
if allMethods == nil {
allMethods = markComplete
var methods []*Func
var seen objset
addMethod := func(m *Func, explicit bool) {
switch alt := seen.insert(m); {
case alt == nil:
methods = append(methods, m)
case explicit || !Identical(m.Type(), alt.Type()):
panic("duplicate method " + m.name)
default:
// silently drop method m
}
}
for _, m := range t.methods {
addMethod(m, true)
}
for _, typ := range t.embeddeds {
typ := typ.Underlying().(*Interface)
typ.Complete()
for _, m := range typ.allMethods {
addMethod(m, false)
}
}
if methods != nil {
sort.Sort(byUniqueMethodName(methods))
t.allMethods = methods
}
t.allMethods = allMethods
return t
}

260
src/go/types/typexpr.go
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@ -472,171 +472,127 @@ func (check *Checker) declareInSet(oset *objset, pos token.Pos, obj Object) bool
}
func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, def *Named) {
// fast-track empty interface
if iface.Methods.List == nil {
ityp.allMethods = markComplete
return
}
for _, f := range iface.Methods.List {
if len(f.Names) > 0 {
// We have a method with name f.Names[0].
// (The parser ensures that there's only one method
// and we don't care if a constructed AST has more.)
name := f.Names[0]
if name.Name == "_" {
check.errorf(name.Pos(), "invalid method name _")
continue // ignore
}
// collect embedded interfaces
// Only needed for printing and API. Delay collection
// to end of type-checking (for package-global interfaces)
// when all types are complete. Local interfaces are handled
// after each statement (as each statement processes delayed
// functions).
interfaceContext := check.context // capture for use in closure below
check.later(func() {
if trace {
check.trace(iface.Pos(), "-- delayed checking embedded interfaces of %v", iface)
check.indent++
defer func() {
check.indent--
}()
}
// The context must be restored since for local interfaces
// delayed functions are processed after each statement
// (was issue #24140).
defer func(ctxt context) {
check.context = ctxt
}(check.context)
check.context = interfaceContext
for _, f := range iface.Methods.List {
if len(f.Names) == 0 {
typ := check.indirectType(f.Type)
// typ should be a named type denoting an interface
// (the parser will make sure it's a named type but
// constructed ASTs may be wrong).
if typ == Typ[Invalid] {
continue // error reported before
typ := check.indirectType(f.Type)
sig, _ := typ.(*Signature)
if sig == nil {
if typ != Typ[Invalid] {
check.invalidAST(f.Type.Pos(), "%s is not a method signature", typ)
}
embed, _ := typ.Underlying().(*Interface)
if embed == nil {
continue // ignore
}
// use named receiver type if available (for better error messages)
var recvTyp Type = ityp
if def != nil {
recvTyp = def
}
sig.recv = NewVar(name.Pos(), check.pkg, "", recvTyp)
m := NewFunc(name.Pos(), check.pkg, name.Name, sig)
check.recordDef(name, m)
ityp.methods = append(ityp.methods, m)
} else {
// We have an embedded interface and f.Type is its
// (possibly qualified) embedded type name. Collect
// it if it's a valid interface.
typ := check.typ(f.Type)
if _, ok := underlying(typ).(*Interface); !ok {
if typ != Typ[Invalid] {
check.errorf(f.Type.Pos(), "%s is not an interface", typ)
continue
}
// Correct embedded interfaces must be complete -
// don't just assert, but report error since this
// used to be the underlying cause for issue #18395.
if embed.allMethods == nil {
check.dump("%v: incomplete embedded interface %s", f.Type.Pos(), typ)
unreachable()
}
// collect interface
ityp.embeddeds = append(ityp.embeddeds, typ)
continue
}
}
// sort to match NewInterface/NewInterface2
// TODO(gri) we may be able to switch to source order
sort.Stable(byUniqueTypeName(ityp.embeddeds))
})
// compute method set
var tname *TypeName
var path []*TypeName
if def != nil {
tname = def.obj
path = []*TypeName{tname}
ityp.embeddeds = append(ityp.embeddeds, typ)
check.posMap[ityp] = append(check.posMap[ityp], f.Type.Pos())
}
}
info := check.infoFromTypeLit(check.scope, iface, tname, path)
if info == nil || info == &emptyIfaceInfo {
// we got an error or the empty interface - exit early
if len(ityp.methods) == 0 && len(ityp.embeddeds) == 0 {
// empty interface
ityp.allMethods = markComplete
return
}
// use named receiver type if available (for better error messages)
var recvTyp Type = ityp
if def != nil {
recvTyp = def
}
// Correct receiver type for all methods explicitly declared
// by this interface after we're done with type-checking at
// this level. See comment below for details.
check.later(func() {
for _, m := range ityp.methods {
m.typ.(*Signature).recv.typ = recvTyp
}
})
// collect methods
var sigfix []*methodInfo
for i, minfo := range info.methods {
fun := minfo.fun
if fun == nil {
name := minfo.src.Names[0]
pos := name.Pos()
// Don't type-check signature yet - use an
// empty signature now and update it later.
// But set up receiver since we know it and
// its position, and because interface method
// signatures don't get a receiver via regular
// type-checking (there isn't a receiver in the
// method's AST). Setting the receiver type is
// also important for ptrRecv() (see methodset.go).
//
// Note: For embedded methods, the receiver type
// should be the type of the interface that declared
// the methods in the first place. Since we get the
// methods here via methodInfo, which may be computed
// before we have all relevant interface types, we use
// the current interface's type (recvType). This may be
// the type of the interface embedding the interface that
// declared the methods. This doesn't matter for type-
// checking (we only care about the receiver type for
// the ptrRecv predicate, and it's never a pointer recv
// for interfaces), but it matters for go/types clients
// and for printing. We correct the receiver after type-
// checking.
//
// TODO(gri) Consider marking methods signatures
// as incomplete, for better error messages. See
// also the T4 and T5 tests in testdata/cycles2.src.
sig := new(Signature)
sig.recv = NewVar(pos, check.pkg, "", recvTyp)
fun = NewFunc(pos, check.pkg, name.Name, sig)
minfo.fun = fun
check.recordDef(name, fun)
sigfix = append(sigfix, minfo)
}
// fun != nil
if i < info.explicits {
ityp.methods = append(ityp.methods, fun)
}
ityp.allMethods = append(ityp.allMethods, fun)
}
// fix signatures now that we have collected all methods
savedContext := check.context
for _, minfo := range sigfix {
// (possibly embedded) methods must be type-checked within their scope and
// type-checking them must not affect the current context (was issue #23914)
check.context = context{scope: minfo.scope}
typ := check.indirectType(minfo.src.Type)
sig, _ := typ.(*Signature)
if sig == nil {
if typ != Typ[Invalid] {
check.invalidAST(minfo.src.Type.Pos(), "%s is not a method signature", typ)
}
continue // keep method with empty method signature
}
// update signature, but keep recv that was set up before
old := minfo.fun.typ.(*Signature)
sig.recv = old.recv
*old = *sig // update signature (don't replace pointer!)
}
check.context = savedContext
// sort to match NewInterface/NewInterface2
// TODO(gri) we may be able to switch to source order
// sort for API stability
sort.Sort(byUniqueMethodName(ityp.methods))
sort.Stable(byUniqueTypeName(ityp.embeddeds))
if ityp.allMethods == nil {
ityp.allMethods = markComplete
} else {
sort.Sort(byUniqueMethodName(ityp.allMethods))
check.later(func() { check.completeInterface(ityp) })
}
func (check *Checker) completeInterface(ityp *Interface) {
if ityp.allMethods != nil {
return
}
// completeInterface may be called via the LookupFieldOrMethod or
// MissingMethod external API in which case check will be nil. In
// this case, type-checking must be finished and all interfaces
// should have been completed.
if check == nil {
panic("internal error: incomplete interface")
}
if trace {
check.trace(token.NoPos, "complete %s", ityp)
check.indent++
defer func() {
check.indent--
check.trace(token.NoPos, "=> %s", ityp)
}()
}
ityp.allMethods = markComplete // avoid infinite recursion
var methods []*Func
var seen objset
addMethod := func(m *Func, explicit bool) {
switch alt := seen.insert(m); {
case alt == nil:
methods = append(methods, m)
case explicit || !Identical(m.Type(), alt.Type()):
check.errorf(m.pos, "duplicate method %s", m.name)
// We use "other" rather than "previous" here because
// the first declaration seen may not be textually
// earlier in the source.
check.errorf(alt.Pos(), "\tother declaration of %s", m) // secondary error, \t indented
default:
// silently drop method m
}
}
for _, m := range ityp.methods {
addMethod(m, true)
}
posList := check.posMap[ityp]
for i, typ := range ityp.embeddeds {
pos := posList[i] // embedding position
typ := typ.Underlying().(*Interface)
check.completeInterface(typ)
for _, m := range typ.allMethods {
copy := *m
copy.pos = pos // preserve embedding position
addMethod(&copy, false)
}
}
if methods != nil {
sort.Sort(byUniqueMethodName(methods))
ityp.allMethods = methods
}
}

14
test/fixedbugs/bug211.go
View File

@ -1,14 +0,0 @@
// errorcheck
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
type R interface { duplicate() }
type S interface { duplicate() }
type T interface { R; S } // ERROR "duplicate"
func main() {
}