From 4a72be87b354e7ae641ccebfb57242ee24c8d7f4 Mon Sep 17 00:00:00 2001 From: Rob Findley Date: Fri, 16 Jul 2021 19:52:46 -0400 Subject: [PATCH] [dev.typeparams] go/types: move instantiation code to instantiate.go (cleanup) This is a port of CL 333589 to go/types. Change-Id: Ib9fb1b09e10c400e62d20b55ff0558f3a92fc0eb Reviewed-on: https://go-review.googlesource.com/c/go/+/335072 Trust: Robert Findley Run-TryBot: Robert Findley TryBot-Result: Go Bot Reviewed-by: Robert Griesemer --- src/go/types/instantiate.go | 185 +++++++++++++++++++++++++++++++++++ src/go/types/subst.go | 186 +----------------------------------- 2 files changed, 186 insertions(+), 185 deletions(-) diff --git a/src/go/types/instantiate.go b/src/go/types/instantiate.go index 61b9055326..55e34ca0c1 100644 --- a/src/go/types/instantiate.go +++ b/src/go/types/instantiate.go @@ -2,6 +2,9 @@ // 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 types import ( @@ -9,6 +12,106 @@ import ( "go/token" ) +// 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 token.Pos, typ Type, targs []Type, posList []token.Pos, verify bool) (res Type) { + if verify && check == nil { + panic("cannot have nil receiver if verify is set") + } + + if check != nil && 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(atPos(pos), _Todo, "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 token.Pos, typ Type, targs []Type, verify bool) (res Type) { @@ -25,3 +128,85 @@ func (check *Checker) InstantiateLazy(pos token.Pos, typ Type, targs []Type, ver 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 token.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(atPos(pos), 0, "%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(atPos(pos), 0, "%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. + // TODO(rFindley) should this use parentheses rather than ':' for qualification? + check.softErrorf(atPos(pos), _Todo, + "%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s", + targ, tpar.bound, wrong, m, + ) + } else { + check.softErrorf(atPos(pos), 0, "%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(atPos(pos), _Todo, "%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(atPos(pos), 0, "%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(atPos(pos), _Todo, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, targ, iface.typeSet().types) + return false + } + + return true +} diff --git a/src/go/types/subst.go b/src/go/types/subst.go index d367369158..ec85a6bfc4 100644 --- a/src/go/types/subst.go +++ b/src/go/types/subst.go @@ -2,9 +2,7 @@ // 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 types @@ -56,188 +54,6 @@ func (m *substMap) lookup(tpar *TypeParam) Type { 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 token.Pos, typ Type, targs []Type, posList []token.Pos, verify bool) (res Type) { - if verify && check == nil { - panic("cannot have nil receiver if verify is set") - } - - if check != nil && 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(atPos(pos), _Todo, "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 token.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(atPos(pos), 0, "%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(atPos(pos), 0, "%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. - // TODO(rFindley) should this use parentheses rather than ':' for qualification? - check.softErrorf(atPos(pos), _Todo, - "%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s", - targ, tpar.bound, wrong, m, - ) - } else { - check.softErrorf(atPos(pos), 0, "%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(atPos(pos), _Todo, "%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(atPos(pos), 0, "%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(atPos(pos), _Todo, "%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