// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
+// This file implements instantiation of generic types
+// through substitution of type parameters by type arguments.
+
package types2
import (
"fmt"
)
+// Instantiate instantiates the type typ with the given type arguments
+// targs. To check type constraint satisfaction, verify must be set.
+// pos and posList correspond to the instantiation and type argument
+// positions respectively; posList may be nil or shorter than the number
+// of type arguments provided.
+// typ must be a *Named or a *Signature type, and its number of type
+// parameters must match the number of provided type arguments.
+// The receiver (check) may be nil if and only if verify is not set.
+// The result is a new, instantiated (not generic) type of the same kind
+// (either a *Named or a *Signature).
+// Any methods attached to a *Named are simply copied; they are not
+// instantiated.
+func (check *Checker) Instantiate(pos syntax.Pos, typ Type, targs []Type, posList []syntax.Pos, verify bool) (res Type) {
+ if verify && check == nil {
+ panic("cannot have nil receiver if verify is set")
+ }
+
+ if check != nil && check.conf.Trace {
+ check.trace(pos, "-- instantiating %s with %s", typ, typeListString(targs))
+ check.indent++
+ defer func() {
+ check.indent--
+ var under Type
+ if res != nil {
+ // Calling under() here may lead to endless instantiations.
+ // Test case: type T[P any] T[P]
+ // TODO(gri) investigate if that's a bug or to be expected.
+ under = res.Underlying()
+ }
+ check.trace(pos, "=> %s (under = %s)", res, under)
+ }()
+ }
+
+ assert(len(posList) <= len(targs))
+
+ // TODO(gri) What is better here: work with TypeParams, or work with TypeNames?
+ var tparams []*TypeName
+ switch t := typ.(type) {
+ case *Named:
+ tparams = t.TParams()
+ case *Signature:
+ tparams = t.tparams
+ defer func() {
+ // If we had an unexpected failure somewhere don't panic below when
+ // asserting res.(*Signature). Check for *Signature in case Typ[Invalid]
+ // is returned.
+ if _, ok := res.(*Signature); !ok {
+ return
+ }
+ // If the signature doesn't use its type parameters, subst
+ // will not make a copy. In that case, make a copy now (so
+ // we can set tparams to nil w/o causing side-effects).
+ if t == res {
+ copy := *t
+ res = ©
+ }
+ // After instantiating a generic signature, it is not generic
+ // anymore; we need to set tparams to nil.
+ res.(*Signature).tparams = nil
+ }()
+ default:
+ // only types and functions can be generic
+ panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ))
+ }
+
+ // the number of supplied types must match the number of type parameters
+ if len(targs) != len(tparams) {
+ // TODO(gri) provide better error message
+ if check != nil {
+ check.errorf(pos, "got %d arguments but %d type parameters", len(targs), len(tparams))
+ return Typ[Invalid]
+ }
+ panic(fmt.Sprintf("%v: got %d arguments but %d type parameters", pos, len(targs), len(tparams)))
+ }
+
+ if len(tparams) == 0 {
+ return typ // nothing to do (minor optimization)
+ }
+
+ smap := makeSubstMap(tparams, targs)
+
+ // check bounds
+ if verify {
+ for i, tname := range tparams {
+ // best position for error reporting
+ pos := pos
+ if i < len(posList) {
+ pos = posList[i]
+ }
+ // stop checking bounds after the first failure
+ if !check.satisfies(pos, targs[i], tname.typ.(*TypeParam), smap) {
+ break
+ }
+ }
+ }
+
+ return check.subst(pos, typ, smap)
+}
+
// InstantiateLazy is like Instantiate, but avoids actually
// instantiating the type until needed.
func (check *Checker) InstantiateLazy(pos syntax.Pos, typ Type, targs []Type, verify bool) (res Type) {
verify: verify,
}
}
+
+// satisfies reports whether the type argument targ satisfies the constraint of type parameter
+// parameter tpar (after any of its type parameters have been substituted through smap).
+// A suitable error is reported if the result is false.
+// TODO(gri) This should be a method of interfaces or type sets.
+func (check *Checker) satisfies(pos syntax.Pos, targ Type, tpar *TypeParam, smap *substMap) bool {
+ iface := tpar.Bound()
+ if iface.Empty() {
+ return true // no type bound
+ }
+
+ // The type parameter bound is parameterized with the same type parameters
+ // as the instantiated type; before we can use it for bounds checking we
+ // need to instantiate it with the type arguments with which we instantiate
+ // the parameterized type.
+ iface = check.subst(pos, iface, smap).(*Interface)
+
+ // targ must implement iface (methods)
+ // - check only if we have methods
+ if iface.NumMethods() > 0 {
+ // If the type argument is a pointer to a type parameter, the type argument's
+ // method set is empty.
+ // TODO(gri) is this what we want? (spec question)
+ if base, isPtr := deref(targ); isPtr && asTypeParam(base) != nil {
+ check.errorf(pos, "%s has no methods", targ)
+ return false
+ }
+ if m, wrong := check.missingMethod(targ, iface, true); m != nil {
+ // TODO(gri) needs to print updated name to avoid major confusion in error message!
+ // (print warning for now)
+ // Old warning:
+ // check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", targ, tpar.bound, iface, m)
+ if m.name == "==" {
+ // We don't want to report "missing method ==".
+ check.softErrorf(pos, "%s does not satisfy comparable", targ)
+ } else if wrong != nil {
+ // TODO(gri) This can still report uninstantiated types which makes the error message
+ // more difficult to read then necessary.
+ check.softErrorf(pos,
+ "%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s",
+ targ, tpar.bound, wrong, m,
+ )
+ } else {
+ check.softErrorf(pos, "%s does not satisfy %s (missing method %s)", targ, tpar.bound, m.name)
+ }
+ return false
+ }
+ }
+
+ // targ's underlying type must also be one of the interface types listed, if any
+ if iface.typeSet().types == nil {
+ return true // nothing to do
+ }
+
+ // If targ is itself a type parameter, each of its possible types, but at least one, must be in the
+ // list of iface types (i.e., the targ type list must be a non-empty subset of the iface types).
+ if targ := asTypeParam(targ); targ != nil {
+ targBound := targ.Bound()
+ if targBound.typeSet().types == nil {
+ check.softErrorf(pos, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
+ return false
+ }
+ return iface.is(func(typ Type, tilde bool) bool {
+ // TODO(gri) incorporate tilde information!
+ if !iface.isSatisfiedBy(typ) {
+ // TODO(gri) match this error message with the one below (or vice versa)
+ check.softErrorf(pos, "%s does not satisfy %s (%s type constraint %s not found in %s)", targ, tpar.bound, targ, typ, iface.typeSet().types)
+ return false
+ }
+ return true
+ })
+ }
+
+ // Otherwise, targ's type or underlying type must also be one of the interface types listed, if any.
+ if !iface.isSatisfiedBy(targ) {
+ check.softErrorf(pos, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, targ, iface.typeSet().types)
+ return false
+ }
+
+ return true
+}
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
-// This file implements instantiation of generic types
-// through substitution of type parameters by actual
-// types.
+// This file implements type parameter substitution.
package types2
return tpar
}
-// Instantiate instantiates the type typ with the given type arguments
-// targs. To check type constraint satisfaction, verify must be set.
-// pos and posList correspond to the instantiation and type argument
-// positions respectively; posList may be nil or shorter than the number
-// of type arguments provided.
-// typ must be a *Named or a *Signature type, and its number of type
-// parameters must match the number of provided type arguments.
-// The receiver (check) may be nil if and only if verify is not set.
-// The result is a new, instantiated (not generic) type of the same kind
-// (either a *Named or a *Signature).
-// Any methods attached to a *Named are simply copied; they are not
-// instantiated.
-func (check *Checker) Instantiate(pos syntax.Pos, typ Type, targs []Type, posList []syntax.Pos, verify bool) (res Type) {
- if verify && check == nil {
- panic("cannot have nil receiver if verify is set")
- }
-
- if check != nil && check.conf.Trace {
- check.trace(pos, "-- instantiating %s with %s", typ, typeListString(targs))
- check.indent++
- defer func() {
- check.indent--
- var under Type
- if res != nil {
- // Calling under() here may lead to endless instantiations.
- // Test case: type T[P any] T[P]
- // TODO(gri) investigate if that's a bug or to be expected.
- under = res.Underlying()
- }
- check.trace(pos, "=> %s (under = %s)", res, under)
- }()
- }
-
- assert(len(posList) <= len(targs))
-
- // TODO(gri) What is better here: work with TypeParams, or work with TypeNames?
- var tparams []*TypeName
- switch t := typ.(type) {
- case *Named:
- tparams = t.TParams()
- case *Signature:
- tparams = t.tparams
- defer func() {
- // If we had an unexpected failure somewhere don't panic below when
- // asserting res.(*Signature). Check for *Signature in case Typ[Invalid]
- // is returned.
- if _, ok := res.(*Signature); !ok {
- return
- }
- // If the signature doesn't use its type parameters, subst
- // will not make a copy. In that case, make a copy now (so
- // we can set tparams to nil w/o causing side-effects).
- if t == res {
- copy := *t
- res = ©
- }
- // After instantiating a generic signature, it is not generic
- // anymore; we need to set tparams to nil.
- res.(*Signature).tparams = nil
- }()
- default:
- // only types and functions can be generic
- panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ))
- }
-
- // the number of supplied types must match the number of type parameters
- if len(targs) != len(tparams) {
- // TODO(gri) provide better error message
- if check != nil {
- check.errorf(pos, "got %d arguments but %d type parameters", len(targs), len(tparams))
- return Typ[Invalid]
- }
- panic(fmt.Sprintf("%v: got %d arguments but %d type parameters", pos, len(targs), len(tparams)))
- }
-
- if len(tparams) == 0 {
- return typ // nothing to do (minor optimization)
- }
-
- smap := makeSubstMap(tparams, targs)
-
- // check bounds
- if verify {
- for i, tname := range tparams {
- // best position for error reporting
- pos := pos
- if i < len(posList) {
- pos = posList[i]
- }
- // stop checking bounds after the first failure
- if !check.satisfies(pos, targs[i], tname.typ.(*TypeParam), smap) {
- break
- }
- }
- }
-
- return check.subst(pos, typ, smap)
-}
-
-// satisfies reports whether the type argument targ satisfies the constraint of type parameter
-// parameter tpar (after any of its type parameters have been substituted through smap).
-// A suitable error is reported if the result is false.
-// TODO(gri) This should be a method of interfaces or type sets.
-func (check *Checker) satisfies(pos syntax.Pos, targ Type, tpar *TypeParam, smap *substMap) bool {
- iface := tpar.Bound()
- if iface.Empty() {
- return true // no type bound
- }
-
- // The type parameter bound is parameterized with the same type parameters
- // as the instantiated type; before we can use it for bounds checking we
- // need to instantiate it with the type arguments with which we instantiate
- // the parameterized type.
- iface = check.subst(pos, iface, smap).(*Interface)
-
- // targ must implement iface (methods)
- // - check only if we have methods
- if iface.NumMethods() > 0 {
- // If the type argument is a pointer to a type parameter, the type argument's
- // method set is empty.
- // TODO(gri) is this what we want? (spec question)
- if base, isPtr := deref(targ); isPtr && asTypeParam(base) != nil {
- check.errorf(pos, "%s has no methods", targ)
- return false
- }
- if m, wrong := check.missingMethod(targ, iface, true); m != nil {
- // TODO(gri) needs to print updated name to avoid major confusion in error message!
- // (print warning for now)
- // Old warning:
- // check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", targ, tpar.bound, iface, m)
- if m.name == "==" {
- // We don't want to report "missing method ==".
- check.softErrorf(pos, "%s does not satisfy comparable", targ)
- } else if wrong != nil {
- // TODO(gri) This can still report uninstantiated types which makes the error message
- // more difficult to read then necessary.
- check.softErrorf(pos,
- "%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s",
- targ, tpar.bound, wrong, m,
- )
- } else {
- check.softErrorf(pos, "%s does not satisfy %s (missing method %s)", targ, tpar.bound, m.name)
- }
- return false
- }
- }
-
- // targ's underlying type must also be one of the interface types listed, if any
- if iface.typeSet().types == nil {
- return true // nothing to do
- }
-
- // If targ is itself a type parameter, each of its possible types, but at least one, must be in the
- // list of iface types (i.e., the targ type list must be a non-empty subset of the iface types).
- if targ := asTypeParam(targ); targ != nil {
- targBound := targ.Bound()
- if targBound.typeSet().types == nil {
- check.softErrorf(pos, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
- return false
- }
- return iface.is(func(typ Type, tilde bool) bool {
- // TODO(gri) incorporate tilde information!
- if !iface.isSatisfiedBy(typ) {
- // TODO(gri) match this error message with the one below (or vice versa)
- check.softErrorf(pos, "%s does not satisfy %s (%s type constraint %s not found in %s)", targ, tpar.bound, targ, typ, iface.typeSet().types)
- return false
- }
- return true
- })
- }
-
- // Otherwise, targ's type or underlying type must also be one of the interface types listed, if any.
- if !iface.isSatisfiedBy(targ) {
- check.softErrorf(pos, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, targ, iface.typeSet().types)
- return false
- }
-
- return true
-}
-
// subst returns the type typ with its type parameters tpars replaced by
// the corresponding type arguments targs, recursively.
// subst is functional in the sense that it doesn't modify the incoming