// Unify parameter and argument types for generic parameters with typed arguments
// and collect the indices of generic parameters with untyped arguments.
// Terminology: generic parameter = function parameter with a type-parameterized type
- u := newUnifier(false)
- u.x.init(tparams)
+ u := newUnifier(tparams)
// Set the type arguments which we know already.
for i, targ := range targs {
if targ != nil {
- u.x.set(i, targ)
+ u.set(i, targ)
}
}
errorf := func(kind string, tpar, targ Type, arg *operand) {
// provide a better error message if we can
- targs, index := u.x.types()
+ targs, index := u.inferred()
if index == 0 {
// The first type parameter couldn't be inferred.
// If none of them could be inferred, don't try
// If we've got all type arguments, we're done.
var index int
- targs, index = u.x.types()
+ targs, index = u.inferred()
if index < 0 {
return targs
}
}
// If we've got all type arguments, we're done.
- targs, index = u.x.types()
+ targs, index = u.inferred()
if index < 0 {
return targs
}
}()
}
- // Setup bidirectional unification between constraints
- // and the corresponding type arguments (which may be nil!).
- u := newUnifier(false)
- u.x.init(tparams)
- u.y = u.x // type parameters between LHS and RHS of unification are identical
+ // Unify type parameters with their constraints.
+ u := newUnifier(tparams)
// Set the type arguments which we know already.
for i, targ := range targs {
if targ != nil {
- u.x.set(i, targ)
+ u.set(i, targ)
}
}
// here could handle the respective type parameters only,
// but that will come at a cost of extra complexity which
// may not be worth it.)
- for n := u.x.unknowns(); n > 0; {
+ for n := u.unknowns(); n > 0; {
nn := n
for i, tpar := range tparams {
u.tracef("core(%s) = %s (single = %v)", tpar, core, single)
}
// A type parameter can be unified with its core type in two cases.
- tx := u.x.at(i)
+ tx := u.at(i)
switch {
case tx != nil:
// The corresponding type argument tx is known.
// The corresponding type argument tx is unknown and there's a single
// specific type and no tilde.
// In this case the type argument must be that single type; set it.
- u.x.set(i, core.typ)
+ u.set(i, core.typ)
default:
// Unification is not possible and no progress was made.
}
// The number of known type arguments may have changed.
- nn = u.x.unknowns()
+ nn = u.unknowns()
if nn == 0 {
break // all type arguments are known
}
n = nn
}
- // u.x.types() now contains the incoming type arguments plus any additional type
+ // u.inferred() now contains the incoming type arguments plus any additional type
// arguments which were inferred from core terms. The newly inferred non-nil
// entries may still contain references to other type parameters.
// For instance, for [A any, B interface{ []C }, C interface{ *A }], if A == int
// was given, unification produced the type list [int, []C, *A]. We eliminate the
// remaining type parameters by substituting the type parameters in this type list
// until nothing changes anymore.
- types, _ = u.x.types()
+ types, _ = u.inferred()
if debug {
for i, targ := range targs {
assert(targ == nil || types[i] == targ)
"strings"
)
-// The unifier maintains two separate sets of type parameters x and y
-// which are used to resolve type parameters in the x and y arguments
-// provided to the unify call. For unidirectional unification, only
-// one of these sets (say x) is provided, and then type parameters are
-// only resolved for the x argument passed to unify, not the y argument
-// (even if that also contains possibly the same type parameters).
-//
-// For bidirectional unification, both sets are provided. This enables
-// unification to go from argument to parameter type and vice versa.
-// For constraint type inference, we use bidirectional unification
-// where both the x and y type parameters are identical. This is done
-// by setting up one of them (using init) and then assigning its value
-// to the other.
-
const (
// Upper limit for recursion depth. Used to catch infinite recursions
// due to implementation issues (e.g., see issues #48619, #48656).
// x ≢ y types x and y cannot be unified
// [p, q, ...] ➞ [x, y, ...] mapping from type parameters to types
traceInference = false
+
+ // If exactUnification is set, unification requires (named) types
+ // to match exactly. If it is not set, the underlying types are
+ // considered when unification is known to fail otherwise.
+ exactUnification = false
)
-// A unifier maintains the current type parameters for x and y
-// and the respective types inferred for each type parameter.
+// A unifier maintains a list of type parameters and
+// corresponding types inferred for each type parameter.
// A unifier is created by calling newUnifier.
type unifier struct {
- exact bool
- x, y tparamsList // x and y must initialized via tparamsList.init
- types []Type // inferred types, shared by x and y
- depth int // recursion depth during unification
+ tparams []*TypeParam
+ // For each tparams element, there is a corresponding type slot index in indices.
+ // index < 0: unifier.types[-index-1] == nil
+ // index == 0: no type slot allocated yet
+ // index > 0: unifier.types[index-1] == typ
+ // Joined tparams elements share the same type slot and thus have the same index.
+ // By using a negative index for nil types we don't need to check unifier.types
+ // to see if we have a type or not.
+ indices []int // len(indices) == len(tparams)
+ types []Type // inferred types, shared by x and y
+ depth int // recursion depth during unification
}
-// newUnifier returns a new unifier.
-// If exact is set, unification requires unified types to match
-// exactly. If exact is not set, a named type's underlying type
-// is considered if unification would fail otherwise, and the
-// direction of channels is ignored.
-// TODO(gri) exact is not set anymore by a caller. Consider removing it.
-func newUnifier(exact bool) *unifier {
- u := &unifier{exact: exact}
- u.x.unifier = u
- u.y.unifier = u
- return u
+// newUnifier returns a new unifier initialized with the given type parameters.
+// The type parameters must be in the order in which they appear in their declaration
+// (this ensures that the tparams indices match the respective type parameter index).
+func newUnifier(tparams []*TypeParam) *unifier {
+ if debug {
+ for i, tpar := range tparams {
+ assert(i == tpar.index)
+ }
+ }
+ return &unifier{
+ tparams: tparams,
+ indices: make([]int, len(tparams)),
+ }
}
// unify attempts to unify x and y and reports whether it succeeded.
+// As a side-effect, types may be inferred for type parameters.
func (u *unifier) unify(x, y Type) bool {
return u.nify(x, y, nil)
}
fmt.Println(strings.Repeat(". ", u.depth) + sprintf(nil, true, format, args...))
}
-// A tparamsList describes a list of type parameters and the types inferred for them.
-type tparamsList struct {
- unifier *unifier
- tparams []*TypeParam
- // For each tparams element, there is a corresponding type slot index in indices.
- // index < 0: unifier.types[-index-1] == nil
- // index == 0: no type slot allocated yet
- // index > 0: unifier.types[index-1] == typ
- // Joined tparams elements share the same type slot and thus have the same index.
- // By using a negative index for nil types we don't need to check unifier.types
- // to see if we have a type or not.
- indices []int // len(d.indices) == len(d.tparams)
-}
-
-// String returns a string representation for a tparamsList. For debugging.
-func (d *tparamsList) String() string {
+// String returns a string representation of the mapping from
+// type parameters to types.
+func (u *unifier) String() string {
var buf bytes.Buffer
w := newTypeWriter(&buf, nil)
w.byte('[')
- for i, tpar := range d.tparams {
+ for i, tpar := range u.tparams {
if i > 0 {
w.string(", ")
}
w.typ(tpar)
w.string(": ")
- w.typ(d.at(i))
+ w.typ(u.at(i))
}
w.byte(']')
return buf.String()
}
-// init initializes d with the given type parameters.
-// The type parameters must be in the order in which they appear in their declaration
-// (this ensures that the tparams indices match the respective type parameter index).
-func (d *tparamsList) init(tparams []*TypeParam) {
- if len(tparams) == 0 {
- return
- }
- if debug {
- for i, tpar := range tparams {
- assert(i == tpar.index)
- }
- }
- d.tparams = tparams
- d.indices = make([]int, len(tparams))
-}
-
-// join unifies the i'th type parameter of x with the j'th type parameter of y.
-// If both type parameters already have a type associated with them and they are
-// not joined, join fails and returns false.
+// join unifies the i'th type parameter with the j'th type parameter.
+// If both type parameters already have a type associated with them
+// and they are not joined, join fails and returns false.
func (u *unifier) join(i, j int) bool {
if traceInference {
- u.tracef("%s ⇄ %s", u.x.tparams[i], u.y.tparams[j])
+ u.tracef("%s ⇄ %s", u.tparams[i], u.tparams[j])
}
- ti := u.x.indices[i]
- tj := u.y.indices[j]
+ ti := u.indices[i]
+ tj := u.indices[j]
switch {
case ti == 0 && tj == 0:
// Neither type parameter has a type slot associated with them.
// Allocate a new joined nil type slot (negative index).
u.types = append(u.types, nil)
- u.x.indices[i] = -len(u.types)
- u.y.indices[j] = -len(u.types)
+ u.indices[i] = -len(u.types)
+ u.indices[j] = -len(u.types)
case ti == 0:
- // The type parameter for x has no type slot yet. Use slot of y.
- u.x.indices[i] = tj
+ // The type parameter (with index) i has no type slot yet. Use slot of j.
+ u.indices[i] = tj
case tj == 0:
- // The type parameter for y has no type slot yet. Use slot of x.
- u.y.indices[j] = ti
+ // The type parameter (with index) j has no type slot yet. Use slot of i.
+ u.indices[j] = ti
// Both type parameters have a slot: ti != 0 && tj != 0.
case ti == tj:
// TODO(gri) Should we check if types are identical? Investigate.
return false
case ti > 0:
- // Only the type parameter for x has an inferred type. Use x slot for y.
- u.y.setIndex(j, ti)
+ // Only the type parameter (with index) i has an inferred type. Use i slot for j.
+ u.setIndex(j, ti)
// This case is handled like the default case.
// case tj > 0:
// // Only the type parameter for y has an inferred type. Use y slot for x.
- // u.x.setIndex(i, tj)
+ // u.setIndex(i, tj)
default:
- // Neither type parameter has an inferred type. Use y slot for x
- // (or x slot for y, it doesn't matter).
- u.x.setIndex(i, tj)
+ // Neither type parameter has an inferred type. Use j slot for i
+ // (or i slot for j, it doesn't matter).
+ u.setIndex(i, tj)
}
return true
}
-// If typ is a type parameter of d, index returns the type parameter index.
+// If typ is a type parameter recorded with u, index returns the type parameter index.
// Otherwise, the result is < 0.
-func (d *tparamsList) index(typ Type) int {
+func (u *unifier) index(typ Type) int {
if tpar, ok := typ.(*TypeParam); ok {
- return tparamIndex(d.tparams, tpar)
+ return tparamIndex(u.tparams, tpar)
}
return -1
}
// setIndex sets the type slot index for the i'th type parameter
// (and all its joined parameters) to tj. The type parameter
// must have a (possibly nil) type slot associated with it.
-func (d *tparamsList) setIndex(i, tj int) {
- ti := d.indices[i]
+func (u *unifier) setIndex(i, tj int) {
+ ti := u.indices[i]
assert(ti != 0 && tj != 0)
- for k, tk := range d.indices {
+ for k, tk := range u.indices {
if tk == ti {
- d.indices[k] = tj
+ u.indices[k] = tj
}
}
}
// at returns the type set for the i'th type parameter; or nil.
-func (d *tparamsList) at(i int) Type {
- if ti := d.indices[i]; ti > 0 {
- return d.unifier.types[ti-1]
+func (u *unifier) at(i int) Type {
+ if ti := u.indices[i]; ti > 0 {
+ return u.types[ti-1]
}
return nil
}
// set sets the type typ for the i'th type parameter;
// typ must not be nil and it must not have been set before.
-func (d *tparamsList) set(i int, typ Type) {
+func (u *unifier) set(i int, typ Type) {
assert(typ != nil)
- u := d.unifier
if traceInference {
- u.tracef("%s ➞ %s", d.tparams[i], typ)
+ u.tracef("%s ➞ %s", u.tparams[i], typ)
}
- switch ti := d.indices[i]; {
+ switch ti := u.indices[i]; {
case ti < 0:
u.types[-ti-1] = typ
- d.setIndex(i, -ti)
+ u.setIndex(i, -ti)
case ti == 0:
u.types = append(u.types, typ)
- d.indices[i] = len(u.types)
+ u.indices[i] = len(u.types)
default:
panic("type already set")
}
}
// unknowns returns the number of type parameters for which no type has been set yet.
-func (d *tparamsList) unknowns() int {
+func (u *unifier) unknowns() int {
n := 0
- for _, ti := range d.indices {
+ for _, ti := range u.indices {
if ti <= 0 {
n++
}
return n
}
-// types returns the list of inferred types (via unification) for the type parameters
-// described by d, and an index. If all types were inferred, the returned index is < 0.
+// inferred returns the list of inferred types (via unification) for the type parameters
+// recorded with u, and an index. If all types were inferred, the returned index is < 0.
// Otherwise, it is the index of the first type parameter which couldn't be inferred;
// i.e., for which list[index] is nil.
-func (d *tparamsList) types() (list []Type, index int) {
- list = make([]Type, len(d.tparams))
+func (u *unifier) inferred() (list []Type, index int) {
+ list = make([]Type, len(u.tparams))
index = -1
- for i := range d.tparams {
- t := d.at(i)
+ for i := range u.tparams {
+ t := u.at(i)
list[i] = t
if index < 0 && t == nil {
index = i
}
}()
- if !u.exact {
+ if !exactUnification {
// If exact unification is known to fail because we attempt to
// match a type name against an unnamed type literal, consider
// the underlying type of the named type.
}
// Cases where at least one of x or y is a type parameter.
- switch i, j := u.x.index(x), u.y.index(y); {
+ switch i, j := u.index(x), u.index(y); {
case i >= 0 && j >= 0:
// both x and y are type parameters
if u.join(i, j) {
return true
}
// both x and y have an inferred type - they must match
- return u.nifyEq(u.x.at(i), u.y.at(j), p)
+ return u.nifyEq(u.at(i), u.at(j), p)
case i >= 0:
// x is a type parameter, y is not
- if tx := u.x.at(i); tx != nil {
+ if tx := u.at(i); tx != nil {
return u.nifyEq(tx, y, p)
}
// otherwise, infer type from y
- u.x.set(i, y)
+ u.set(i, y)
return true
case j >= 0:
// y is a type parameter, x is not
- if ty := u.y.at(j); ty != nil {
+ if ty := u.at(j); ty != nil {
return u.nifyEq(x, ty, p)
}
// otherwise, infer type from x
- u.y.set(j, x)
+ u.set(j, x)
return true
}
// If we get here and x or y is a type parameter, they are type parameters
// from outside our declaration list. Try to unify their core types, if any
// (see go.dev/issue/50755 for a test case).
- if enableCoreTypeUnification && !u.exact {
+ if enableCoreTypeUnification && !exactUnification {
if isTypeParam(x) && !hasName(y) {
// When considering the type parameter for unification
// we look at the adjusted core term (adjusted core type
// with tilde information).
// If the adjusted core type is a named type N; the
- // corresponding core type is under(N). Since !u.exact
+ // corresponding core type is under(N). Since !exactUnification
// and y doesn't have a name, unification will end up
// comparing under(N) to y, so we can just use the core
// type instead. And we can ignore the tilde because we
case *Chan:
// Two channel types are identical if they have identical value types.
if y, ok := y.(*Chan); ok {
- return (!u.exact || x.dir == y.dir) && u.nify(x.elem, y.elem, p)
+ return (!exactUnification || x.dir == y.dir) && u.nify(x.elem, y.elem, p)
}
case *Named:
// avoid a crash in case of nil type
default:
- panic(sprintf(nil, true, "u.nify(%s, %s), u.x.tparams = %s", x, y, u.x.tparams))
+ panic(sprintf(nil, true, "u.nify(%s, %s), u.tparams = %s", x, y, u.tparams))
}
return false
// Unify parameter and argument types for generic parameters with typed arguments
// and collect the indices of generic parameters with untyped arguments.
// Terminology: generic parameter = function parameter with a type-parameterized type
- u := newUnifier(false)
- u.x.init(tparams)
+ u := newUnifier(tparams)
// Set the type arguments which we know already.
for i, targ := range targs {
if targ != nil {
- u.x.set(i, targ)
+ u.set(i, targ)
}
}
errorf := func(kind string, tpar, targ Type, arg *operand) {
// provide a better error message if we can
- targs, index := u.x.types()
+ targs, index := u.inferred()
if index == 0 {
// The first type parameter couldn't be inferred.
// If none of them could be inferred, don't try
// If we've got all type arguments, we're done.
var index int
- targs, index = u.x.types()
+ targs, index = u.inferred()
if index < 0 {
return targs
}
}
// If we've got all type arguments, we're done.
- targs, index = u.x.types()
+ targs, index = u.inferred()
if index < 0 {
return targs
}
}()
}
- // Setup bidirectional unification between constraints
- // and the corresponding type arguments (which may be nil!).
- u := newUnifier(false)
- u.x.init(tparams)
- u.y = u.x // type parameters between LHS and RHS of unification are identical
+ // Unify type parameters with their constraints.
+ u := newUnifier(tparams)
// Set the type arguments which we know already.
for i, targ := range targs {
if targ != nil {
- u.x.set(i, targ)
+ u.set(i, targ)
}
}
// here could handle the respective type parameters only,
// but that will come at a cost of extra complexity which
// may not be worth it.)
- for n := u.x.unknowns(); n > 0; {
+ for n := u.unknowns(); n > 0; {
nn := n
for i, tpar := range tparams {
u.tracef("core(%s) = %s (single = %v)", tpar, core, single)
}
// A type parameter can be unified with its core type in two cases.
- tx := u.x.at(i)
+ tx := u.at(i)
switch {
case tx != nil:
// The corresponding type argument tx is known.
// The corresponding type argument tx is unknown and there's a single
// specific type and no tilde.
// In this case the type argument must be that single type; set it.
- u.x.set(i, core.typ)
+ u.set(i, core.typ)
default:
// Unification is not possible and no progress was made.
}
// The number of known type arguments may have changed.
- nn = u.x.unknowns()
+ nn = u.unknowns()
if nn == 0 {
break // all type arguments are known
}
n = nn
}
- // u.x.types() now contains the incoming type arguments plus any additional type
+ // u.inferred() now contains the incoming type arguments plus any additional type
// arguments which were inferred from core terms. The newly inferred non-nil
// entries may still contain references to other type parameters.
// For instance, for [A any, B interface{ []C }, C interface{ *A }], if A == int
// was given, unification produced the type list [int, []C, *A]. We eliminate the
// remaining type parameters by substituting the type parameters in this type list
// until nothing changes anymore.
- types, _ = u.x.types()
+ types, _ = u.inferred()
if debug {
for i, targ := range targs {
assert(targ == nil || types[i] == targ)
"strings"
)
-// The unifier maintains two separate sets of type parameters x and y
-// which are used to resolve type parameters in the x and y arguments
-// provided to the unify call. For unidirectional unification, only
-// one of these sets (say x) is provided, and then type parameters are
-// only resolved for the x argument passed to unify, not the y argument
-// (even if that also contains possibly the same type parameters).
-//
-// For bidirectional unification, both sets are provided. This enables
-// unification to go from argument to parameter type and vice versa.
-// For constraint type inference, we use bidirectional unification
-// where both the x and y type parameters are identical. This is done
-// by setting up one of them (using init) and then assigning its value
-// to the other.
-
const (
// Upper limit for recursion depth. Used to catch infinite recursions
// due to implementation issues (e.g., see issues #48619, #48656).
// x ≢ y types x and y cannot be unified
// [p, q, ...] ➞ [x, y, ...] mapping from type parameters to types
traceInference = false
+
+ // If exactUnification is set, unification requires (named) types
+ // to match exactly. If it is not set, the underlying types are
+ // considered when unification is known to fail otherwise.
+ exactUnification = false
)
-// A unifier maintains the current type parameters for x and y
-// and the respective types inferred for each type parameter.
+// A unifier maintains a list of type parameters and
+// corresponding types inferred for each type parameter.
// A unifier is created by calling newUnifier.
type unifier struct {
- exact bool
- x, y tparamsList // x and y must initialized via tparamsList.init
- types []Type // inferred types, shared by x and y
- depth int // recursion depth during unification
+ tparams []*TypeParam
+ // For each tparams element, there is a corresponding type slot index in indices.
+ // index < 0: unifier.types[-index-1] == nil
+ // index == 0: no type slot allocated yet
+ // index > 0: unifier.types[index-1] == typ
+ // Joined tparams elements share the same type slot and thus have the same index.
+ // By using a negative index for nil types we don't need to check unifier.types
+ // to see if we have a type or not.
+ indices []int // len(indices) == len(tparams)
+ types []Type // inferred types, shared by x and y
+ depth int // recursion depth during unification
}
-// newUnifier returns a new unifier.
-// If exact is set, unification requires unified types to match
-// exactly. If exact is not set, a named type's underlying type
-// is considered if unification would fail otherwise, and the
-// direction of channels is ignored.
-// TODO(gri) exact is not set anymore by a caller. Consider removing it.
-func newUnifier(exact bool) *unifier {
- u := &unifier{exact: exact}
- u.x.unifier = u
- u.y.unifier = u
- return u
+// newUnifier returns a new unifier initialized with the given type parameters.
+// The type parameters must be in the order in which they appear in their declaration
+// (this ensures that the tparams indices match the respective type parameter index).
+func newUnifier(tparams []*TypeParam) *unifier {
+ if debug {
+ for i, tpar := range tparams {
+ assert(i == tpar.index)
+ }
+ }
+ return &unifier{
+ tparams: tparams,
+ indices: make([]int, len(tparams)),
+ }
}
// unify attempts to unify x and y and reports whether it succeeded.
+// As a side-effect, types may be inferred for type parameters.
func (u *unifier) unify(x, y Type) bool {
return u.nify(x, y, nil)
}
fmt.Println(strings.Repeat(". ", u.depth) + sprintf(nil, nil, true, format, args...))
}
-// A tparamsList describes a list of type parameters and the types inferred for them.
-type tparamsList struct {
- unifier *unifier
- tparams []*TypeParam
- // For each tparams element, there is a corresponding type slot index in indices.
- // index < 0: unifier.types[-index-1] == nil
- // index == 0: no type slot allocated yet
- // index > 0: unifier.types[index-1] == typ
- // Joined tparams elements share the same type slot and thus have the same index.
- // By using a negative index for nil types we don't need to check unifier.types
- // to see if we have a type or not.
- indices []int // len(d.indices) == len(d.tparams)
-}
-
-// String returns a string representation for a tparamsList. For debugging.
-func (d *tparamsList) String() string {
+// String returns a string representation of the mapping from
+// type parameters to types.
+func (u *unifier) String() string {
var buf bytes.Buffer
w := newTypeWriter(&buf, nil)
w.byte('[')
- for i, tpar := range d.tparams {
+ for i, tpar := range u.tparams {
if i > 0 {
w.string(", ")
}
w.typ(tpar)
w.string(": ")
- w.typ(d.at(i))
+ w.typ(u.at(i))
}
w.byte(']')
return buf.String()
}
-// init initializes d with the given type parameters.
-// The type parameters must be in the order in which they appear in their declaration
-// (this ensures that the tparams indices match the respective type parameter index).
-func (d *tparamsList) init(tparams []*TypeParam) {
- if len(tparams) == 0 {
- return
- }
- if debug {
- for i, tpar := range tparams {
- assert(i == tpar.index)
- }
- }
- d.tparams = tparams
- d.indices = make([]int, len(tparams))
-}
-
-// join unifies the i'th type parameter of x with the j'th type parameter of y.
-// If both type parameters already have a type associated with them and they are
-// not joined, join fails and returns false.
+// join unifies the i'th type parameter with the j'th type parameter.
+// If both type parameters already have a type associated with them
+// and they are not joined, join fails and returns false.
func (u *unifier) join(i, j int) bool {
if traceInference {
- u.tracef("%s ⇄ %s", u.x.tparams[i], u.y.tparams[j])
+ u.tracef("%s ⇄ %s", u.tparams[i], u.tparams[j])
}
- ti := u.x.indices[i]
- tj := u.y.indices[j]
+ ti := u.indices[i]
+ tj := u.indices[j]
switch {
case ti == 0 && tj == 0:
// Neither type parameter has a type slot associated with them.
// Allocate a new joined nil type slot (negative index).
u.types = append(u.types, nil)
- u.x.indices[i] = -len(u.types)
- u.y.indices[j] = -len(u.types)
+ u.indices[i] = -len(u.types)
+ u.indices[j] = -len(u.types)
case ti == 0:
- // The type parameter for x has no type slot yet. Use slot of y.
- u.x.indices[i] = tj
+ // The type parameter (with index) i has no type slot yet. Use slot of j.
+ u.indices[i] = tj
case tj == 0:
- // The type parameter for y has no type slot yet. Use slot of x.
- u.y.indices[j] = ti
+ // The type parameter (with index) j has no type slot yet. Use slot of i.
+ u.indices[j] = ti
// Both type parameters have a slot: ti != 0 && tj != 0.
case ti == tj:
// TODO(gri) Should we check if types are identical? Investigate.
return false
case ti > 0:
- // Only the type parameter for x has an inferred type. Use x slot for y.
- u.y.setIndex(j, ti)
+ // Only the type parameter (with index) i has an inferred type. Use i slot for j.
+ u.setIndex(j, ti)
// This case is handled like the default case.
// case tj > 0:
// // Only the type parameter for y has an inferred type. Use y slot for x.
- // u.x.setIndex(i, tj)
+ // u.setIndex(i, tj)
default:
- // Neither type parameter has an inferred type. Use y slot for x
- // (or x slot for y, it doesn't matter).
- u.x.setIndex(i, tj)
+ // Neither type parameter has an inferred type. Use j slot for i
+ // (or i slot for j, it doesn't matter).
+ u.setIndex(i, tj)
}
return true
}
-// If typ is a type parameter of d, index returns the type parameter index.
+// If typ is a type parameter recorded with u, index returns the type parameter index.
// Otherwise, the result is < 0.
-func (d *tparamsList) index(typ Type) int {
+func (u *unifier) index(typ Type) int {
if tpar, ok := typ.(*TypeParam); ok {
- return tparamIndex(d.tparams, tpar)
+ return tparamIndex(u.tparams, tpar)
}
return -1
}
// setIndex sets the type slot index for the i'th type parameter
// (and all its joined parameters) to tj. The type parameter
// must have a (possibly nil) type slot associated with it.
-func (d *tparamsList) setIndex(i, tj int) {
- ti := d.indices[i]
+func (u *unifier) setIndex(i, tj int) {
+ ti := u.indices[i]
assert(ti != 0 && tj != 0)
- for k, tk := range d.indices {
+ for k, tk := range u.indices {
if tk == ti {
- d.indices[k] = tj
+ u.indices[k] = tj
}
}
}
// at returns the type set for the i'th type parameter; or nil.
-func (d *tparamsList) at(i int) Type {
- if ti := d.indices[i]; ti > 0 {
- return d.unifier.types[ti-1]
+func (u *unifier) at(i int) Type {
+ if ti := u.indices[i]; ti > 0 {
+ return u.types[ti-1]
}
return nil
}
// set sets the type typ for the i'th type parameter;
// typ must not be nil and it must not have been set before.
-func (d *tparamsList) set(i int, typ Type) {
+func (u *unifier) set(i int, typ Type) {
assert(typ != nil)
- u := d.unifier
if traceInference {
- u.tracef("%s ➞ %s", d.tparams[i], typ)
+ u.tracef("%s ➞ %s", u.tparams[i], typ)
}
- switch ti := d.indices[i]; {
+ switch ti := u.indices[i]; {
case ti < 0:
u.types[-ti-1] = typ
- d.setIndex(i, -ti)
+ u.setIndex(i, -ti)
case ti == 0:
u.types = append(u.types, typ)
- d.indices[i] = len(u.types)
+ u.indices[i] = len(u.types)
default:
panic("type already set")
}
}
// unknowns returns the number of type parameters for which no type has been set yet.
-func (d *tparamsList) unknowns() int {
+func (u *unifier) unknowns() int {
n := 0
- for _, ti := range d.indices {
+ for _, ti := range u.indices {
if ti <= 0 {
n++
}
return n
}
-// types returns the list of inferred types (via unification) for the type parameters
-// described by d, and an index. If all types were inferred, the returned index is < 0.
+// inferred returns the list of inferred types (via unification) for the type parameters
+// recorded with u, and an index. If all types were inferred, the returned index is < 0.
// Otherwise, it is the index of the first type parameter which couldn't be inferred;
// i.e., for which list[index] is nil.
-func (d *tparamsList) types() (list []Type, index int) {
- list = make([]Type, len(d.tparams))
+func (u *unifier) inferred() (list []Type, index int) {
+ list = make([]Type, len(u.tparams))
index = -1
- for i := range d.tparams {
- t := d.at(i)
+ for i := range u.tparams {
+ t := u.at(i)
list[i] = t
if index < 0 && t == nil {
index = i
}
}()
- if !u.exact {
+ if !exactUnification {
// If exact unification is known to fail because we attempt to
// match a type name against an unnamed type literal, consider
// the underlying type of the named type.
}
// Cases where at least one of x or y is a type parameter.
- switch i, j := u.x.index(x), u.y.index(y); {
+ switch i, j := u.index(x), u.index(y); {
case i >= 0 && j >= 0:
// both x and y are type parameters
if u.join(i, j) {
return true
}
// both x and y have an inferred type - they must match
- return u.nifyEq(u.x.at(i), u.y.at(j), p)
+ return u.nifyEq(u.at(i), u.at(j), p)
case i >= 0:
// x is a type parameter, y is not
- if tx := u.x.at(i); tx != nil {
+ if tx := u.at(i); tx != nil {
return u.nifyEq(tx, y, p)
}
// otherwise, infer type from y
- u.x.set(i, y)
+ u.set(i, y)
return true
case j >= 0:
// y is a type parameter, x is not
- if ty := u.y.at(j); ty != nil {
+ if ty := u.at(j); ty != nil {
return u.nifyEq(x, ty, p)
}
// otherwise, infer type from x
- u.y.set(j, x)
+ u.set(j, x)
return true
}
// If we get here and x or y is a type parameter, they are type parameters
// from outside our declaration list. Try to unify their core types, if any
// (see go.dev/issue/50755 for a test case).
- if enableCoreTypeUnification && !u.exact {
+ if enableCoreTypeUnification && !exactUnification {
if isTypeParam(x) && !hasName(y) {
// When considering the type parameter for unification
// we look at the adjusted core term (adjusted core type
// with tilde information).
// If the adjusted core type is a named type N; the
- // corresponding core type is under(N). Since !u.exact
+ // corresponding core type is under(N). Since !exactUnification
// and y doesn't have a name, unification will end up
// comparing under(N) to y, so we can just use the core
// type instead. And we can ignore the tilde because we
case *Chan:
// Two channel types are identical if they have identical value types.
if y, ok := y.(*Chan); ok {
- return (!u.exact || x.dir == y.dir) && u.nify(x.elem, y.elem, p)
+ return (!exactUnification || x.dir == y.dir) && u.nify(x.elem, y.elem, p)
}
case *Named:
// avoid a crash in case of nil type
default:
- panic(sprintf(nil, nil, true, "u.nify(%s, %s), u.x.tparams = %s", x, y, u.x.tparams))
+ panic(sprintf(nil, nil, true, "u.nify(%s, %s), u.tparams = %s", x, y, u.tparams))
}
return false