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go/types, types2: change missingMethod to match MissingMethod signature

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This simplifies the use of missingMethod and also opens the door to
further missingMethod-internal simplifications.

Change-Id: I74d9694b6fca67c4103aea04d08916a69ad0e3c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/472495
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
This commit is contained in:
Robert Griesemer 2023-03-01 08:06:42 -08:00 committed by Gopher Robot
parent c10ba768fe
commit 9f2fe2d721
4 changed files with 32 additions and 42 deletions
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3
src/cmd/compile/internal/types2/expr.go
View File

@ -1795,8 +1795,7 @@ func keyVal(x constant.Value) interface{} {
// typeAssertion checks x.(T). The type of x must be an interface.
func (check *Checker) typeAssertion(e syntax.Expr, x *operand, T Type, typeSwitch bool) {
var cause string
method, _ := check.assertableTo(x.typ, T, &cause)
if method == nil {
if check.assertableTo(x.typ, T, &cause) {
return // success
}

34
src/cmd/compile/internal/types2/lookup.go
View File

@ -305,9 +305,7 @@ func (l *instanceLookup) add(inst *Named) {
// present in V have matching types (e.g., for a type assertion x.(T) where
// x is of interface type V).
func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
m, alt := (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
// Only report a wrong type if the alternative method has the same name as m.
return m, alt != nil && alt.name == m.name // alt != nil implies m != nil
return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
}
// missingMethod is like MissingMethod but accepts a *Checker as receiver,
@ -318,17 +316,14 @@ func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType b
// The underlying type of T must be an interface; T (rather than its under-
// lying type) is used for better error messages (reported through *cause).
// The comparator is used to compare signatures.
// If a method is missing and cause is not nil, *cause is set to the error cause.
//
// If a method is missing on T but is found on *T, or if a method is found
// on T when looked up with case-folding, this alternative method is returned
// as the second result.
func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method, alt *Func) {
// If a method is missing and cause is not nil, *cause describes the error.
func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method *Func, wrongType bool) {
methods := under(T).(*Interface).typeSet().methods // T must be an interface
if len(methods) == 0 {
return
}
var alt *Func
if cause != nil {
defer func() {
if method != nil {
@ -347,11 +342,12 @@ func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y
if !static {
continue
}
return m, nil
return m, false
}
if !equivalent(f.typ, m.typ) {
return m, f
alt = f
return m, true
}
}
@ -376,7 +372,7 @@ func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y
// we must have a method (not a struct field)
f, _ := obj.(*Func)
if f == nil {
return m, nil
return m, false
}
// methods may not have a fully set up signature yet
@ -385,7 +381,8 @@ func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y
}
if !found || !equivalent(f.typ, m.typ) {
return m, f
alt = f
return m, f.name == m.name
}
}
@ -470,22 +467,21 @@ func (check *Checker) funcString(f *Func, pkgInfo bool) string {
}
// assertableTo reports whether a value of type V can be asserted to have type T.
// It returns (nil, false) as affirmative answer. Otherwise it returns a missing
// method required by V and whether it is missing or just has the wrong type.
// The receiver may be nil if assertableTo is invoked through an exported API call
// (such as AssertableTo), i.e., when all methods have been type-checked.
// The underlying type of V must be an interface.
// If the result is negative and cause is not nil, *cause is set to the error cause.
// If the result is false and cause is not nil, *cause describes the error.
// TODO(gri) replace calls to this function with calls to newAssertableTo.
func (check *Checker) assertableTo(V, T Type, cause *string) (method, wrongType *Func) {
func (check *Checker) assertableTo(V, T Type, cause *string) bool {
// no static check is required if T is an interface
// spec: "If T is an interface type, x.(T) asserts that the
// dynamic type of x implements the interface T."
if IsInterface(T) {
return
return true
}
// TODO(gri) fix this for generalized interfaces
return check.missingMethod(T, V, false, Identical, cause)
m, _ := check.missingMethod(T, V, false, Identical, cause)
return m == nil
}
// newAssertableTo reports whether a value of type V can be asserted to have type T.

3
src/go/types/expr.go
View File

@ -1742,8 +1742,7 @@ func keyVal(x constant.Value) interface{} {
// typeAssertion checks x.(T). The type of x must be an interface.
func (check *Checker) typeAssertion(e ast.Expr, x *operand, T Type, typeSwitch bool) {
var cause string
method, _ := check.assertableTo(x.typ, T, &cause)
if method == nil {
if check.assertableTo(x.typ, T, &cause) {
return // success
}

34
src/go/types/lookup.go
View File

@ -307,9 +307,7 @@ func (l *instanceLookup) add(inst *Named) {
// present in V have matching types (e.g., for a type assertion x.(T) where
// x is of interface type V).
func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
m, alt := (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
// Only report a wrong type if the alternative method has the same name as m.
return m, alt != nil && alt.name == m.name // alt != nil implies m != nil
return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
}
// missingMethod is like MissingMethod but accepts a *Checker as receiver,
@ -320,17 +318,14 @@ func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType b
// The underlying type of T must be an interface; T (rather than its under-
// lying type) is used for better error messages (reported through *cause).
// The comparator is used to compare signatures.
// If a method is missing and cause is not nil, *cause is set to the error cause.
//
// If a method is missing on T but is found on *T, or if a method is found
// on T when looked up with case-folding, this alternative method is returned
// as the second result.
func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method, alt *Func) {
// If a method is missing and cause is not nil, *cause describes the error.
func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method *Func, wrongType bool) {
methods := under(T).(*Interface).typeSet().methods // T must be an interface
if len(methods) == 0 {
return
}
var alt *Func
if cause != nil {
defer func() {
if method != nil {
@ -349,11 +344,12 @@ func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y
if !static {
continue
}
return m, nil
return m, false
}
if !equivalent(f.typ, m.typ) {
return m, f
alt = f
return m, true
}
}
@ -378,7 +374,7 @@ func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y
// we must have a method (not a struct field)
f, _ := obj.(*Func)
if f == nil {
return m, nil
return m, false
}
// methods may not have a fully set up signature yet
@ -387,7 +383,8 @@ func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y
}
if !found || !equivalent(f.typ, m.typ) {
return m, f
alt = f
return m, f.name == m.name
}
}
@ -472,22 +469,21 @@ func (check *Checker) funcString(f *Func, pkgInfo bool) string {
}
// assertableTo reports whether a value of type V can be asserted to have type T.
// It returns (nil, false) as affirmative answer. Otherwise it returns a missing
// method required by V and whether it is missing or just has the wrong type.
// The receiver may be nil if assertableTo is invoked through an exported API call
// (such as AssertableTo), i.e., when all methods have been type-checked.
// The underlying type of V must be an interface.
// If the result is negative and cause is not nil, *cause is set to the error cause.
// If the result is false and cause is not nil, *cause describes the error.
// TODO(gri) replace calls to this function with calls to newAssertableTo.
func (check *Checker) assertableTo(V, T Type, cause *string) (method, wrongType *Func) {
func (check *Checker) assertableTo(V, T Type, cause *string) bool {
// no static check is required if T is an interface
// spec: "If T is an interface type, x.(T) asserts that the
// dynamic type of x implements the interface T."
if IsInterface(T) {
return
return true
}
// TODO(gri) fix this for generalized interfaces
return check.missingMethod(T, V, false, Identical, cause)
m, _ := check.missingMethod(T, V, false, Identical, cause)
return m == nil
}
// newAssertableTo reports whether a value of type V can be asserted to have type T.