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[dev.typeparams] cmd/compile/internal/types2: factor out constraint satisfaction check
This is a simple move of a block of inlined code into a function to make instantiation more manageable and easier to understand. There is no change in functionality or behavior. Change-Id: I46e7a9ea03527731e1f0219b3402eb03949627c5 Reviewed-on: https://go-review.googlesource.com/c/go/+/322070 Trust: Robert Griesemer <gri@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Robert Griesemer
parent
5770d7a637
commit
155dc0e541
@ -119,85 +119,13 @@ func (check *Checker) instantiate(pos syntax.Pos, typ Type, targs []Type, poslis
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// check bounds
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for i, tname := range tparams {
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tpar := tname.typ.(*TypeParam)
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iface := tpar.Bound()
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if iface.Empty() {
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continue // no type bound
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}
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targ := targs[i]
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// best position for error reporting
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pos := pos
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if i < len(poslist) {
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pos = poslist[i]
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}
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// The type parameter bound is parameterized with the same type parameters
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// as the instantiated type; before we can use it for bounds checking we
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// need to instantiate it with the type arguments with which we instantiate
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// the parameterized type.
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iface = check.subst(pos, iface, smap).(*Interface)
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// targ must implement iface (methods)
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// - check only if we have methods
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check.completeInterface(nopos, iface)
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if len(iface.allMethods) > 0 {
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// If the type argument is a pointer to a type parameter, the type argument's
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// method set is empty.
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// TODO(gri) is this what we want? (spec question)
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if base, isPtr := deref(targ); isPtr && asTypeParam(base) != nil {
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check.errorf(pos, "%s has no methods", targ)
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break
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}
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if m, wrong := check.missingMethod(targ, iface, true); m != nil {
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// TODO(gri) needs to print updated name to avoid major confusion in error message!
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// (print warning for now)
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// Old warning:
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// check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", targ, tpar.bound, iface, m)
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if m.name == "==" {
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// We don't want to report "missing method ==".
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check.softErrorf(pos, "%s does not satisfy comparable", targ)
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} else if wrong != nil {
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// TODO(gri) This can still report uninstantiated types which makes the error message
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// more difficult to read then necessary.
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check.softErrorf(pos,
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"%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s",
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targ, tpar.bound, wrong, m,
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)
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} else {
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check.softErrorf(pos, "%s does not satisfy %s (missing method %s)", targ, tpar.bound, m.name)
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}
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break
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}
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}
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// targ's underlying type must also be one of the interface types listed, if any
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if iface.allTypes == nil {
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continue // nothing to do
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}
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// If targ is itself a type parameter, each of its possible types, but at least one, must be in the
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// list of iface types (i.e., the targ type list must be a non-empty subset of the iface types).
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if targ := asTypeParam(targ); targ != nil {
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targBound := targ.Bound()
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if targBound.allTypes == nil {
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check.softErrorf(pos, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
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break
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}
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for _, t := range unpack(targBound.allTypes) {
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if !iface.isSatisfiedBy(t) {
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// TODO(gri) match this error message with the one below (or vice versa)
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check.softErrorf(pos, "%s does not satisfy %s (%s type constraint %s not found in %s)", targ, tpar.bound, targ, t, iface.allTypes)
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break
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}
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}
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break
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}
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// Otherwise, targ's type or underlying type must also be one of the interface types listed, if any.
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if !iface.isSatisfiedBy(targ) {
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check.softErrorf(pos, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, under(targ), iface.allTypes)
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// stop checking bounds after the first failure
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if !check.satisfies(pos, targs[i], tname.typ.(*TypeParam), smap) {
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break
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}
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}
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@ -205,6 +133,86 @@ func (check *Checker) instantiate(pos syntax.Pos, typ Type, targs []Type, poslis
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return check.subst(pos, typ, smap)
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}
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// satisfies reports whether the type argument targ satisfies the constraint of type parameter
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// parameter tpar (after any of its type parameters have been substituted through smap).
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// A suitable error is reported if the result is false.
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func (check *Checker) satisfies(pos syntax.Pos, targ Type, tpar *TypeParam, smap *substMap) bool {
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iface := tpar.Bound()
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if iface.Empty() {
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return true // no type bound
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}
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// The type parameter bound is parameterized with the same type parameters
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// as the instantiated type; before we can use it for bounds checking we
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// need to instantiate it with the type arguments with which we instantiate
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// the parameterized type.
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iface = check.subst(pos, iface, smap).(*Interface)
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// targ must implement iface (methods)
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// - check only if we have methods
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check.completeInterface(nopos, iface)
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if len(iface.allMethods) > 0 {
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// If the type argument is a pointer to a type parameter, the type argument's
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// method set is empty.
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// TODO(gri) is this what we want? (spec question)
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if base, isPtr := deref(targ); isPtr && asTypeParam(base) != nil {
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check.errorf(pos, "%s has no methods", targ)
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return false
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}
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if m, wrong := check.missingMethod(targ, iface, true); m != nil {
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// TODO(gri) needs to print updated name to avoid major confusion in error message!
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// (print warning for now)
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// Old warning:
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// check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", targ, tpar.bound, iface, m)
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if m.name == "==" {
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// We don't want to report "missing method ==".
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check.softErrorf(pos, "%s does not satisfy comparable", targ)
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} else if wrong != nil {
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// TODO(gri) This can still report uninstantiated types which makes the error message
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// more difficult to read then necessary.
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check.softErrorf(pos,
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"%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s",
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targ, tpar.bound, wrong, m,
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)
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} else {
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check.softErrorf(pos, "%s does not satisfy %s (missing method %s)", targ, tpar.bound, m.name)
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}
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return false
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}
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}
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// targ's underlying type must also be one of the interface types listed, if any
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if iface.allTypes == nil {
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return true // nothing to do
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}
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// If targ is itself a type parameter, each of its possible types, but at least one, must be in the
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// list of iface types (i.e., the targ type list must be a non-empty subset of the iface types).
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if targ := asTypeParam(targ); targ != nil {
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targBound := targ.Bound()
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if targBound.allTypes == nil {
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check.softErrorf(pos, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
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return false
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}
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for _, t := range unpack(targBound.allTypes) {
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if !iface.isSatisfiedBy(t) {
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// TODO(gri) match this error message with the one below (or vice versa)
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check.softErrorf(pos, "%s does not satisfy %s (%s type constraint %s not found in %s)", targ, tpar.bound, targ, t, iface.allTypes)
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return false
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}
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}
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return false
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}
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// Otherwise, targ's type or underlying type must also be one of the interface types listed, if any.
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if !iface.isSatisfiedBy(targ) {
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check.softErrorf(pos, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, under(targ), iface.allTypes)
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return false
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}
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return true
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}
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// subst returns the type typ with its type parameters tpars replaced by
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// the corresponding type arguments targs, recursively.
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// subst is functional in the sense that it doesn't modify the incoming
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