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[dev.typeparams] go/types: factor out constraint satisfaction check

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This is a port of CL 322070 to go/types, adjusted for the different
error reporting API.

Change-Id: I75eafe015b5b00554116527ea021e7a5f9e0343b
Reviewed-on: https://go-review.googlesource.com/c/go/+/324759
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Rob Findley 2021-06-03 12:14:16 -04:00 committed by Robert Findley
parent 7497e57a39
commit 7c8a5be2d6
1 changed files with 83 additions and 74 deletions
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45
src/go/types/subst.go
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@ -121,20 +121,30 @@ func (check *Checker) instantiate(pos token.Pos, typ Type, targs []Type, poslist
// check bounds
for i, tname := range tparams {
tpar := tname.typ.(*_TypeParam)
iface := tpar.Bound()
if iface.Empty() {
continue // no type bound
}
targ := targs[i]
// 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.
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
@ -150,7 +160,7 @@ func (check *Checker) instantiate(pos token.Pos, typ Type, targs []Type, poslist
// 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)
break
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!
@ -171,13 +181,13 @@ func (check *Checker) instantiate(pos token.Pos, typ Type, targs []Type, poslist
} else {
check.softErrorf(atPos(pos), 0, "%s does not satisfy %s (missing method %s)", targ, tpar.bound, m.name)
}
break
return false
}
}
// targ's underlying type must also be one of the interface types listed, if any
if iface.allTypes == nil {
continue // nothing to do
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
@ -186,26 +196,25 @@ func (check *Checker) instantiate(pos token.Pos, typ Type, targs []Type, poslist
targBound := targ.Bound()
if targBound.allTypes == nil {
check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
break
return false
}
for _, t := range unpackType(targBound.allTypes) {
if !iface.isSatisfiedBy(t) {
// 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, t, iface.allTypes)
break
return false
}
}
break
return false
}
// 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 or %s not found in %s)", targ, tpar.bound, targ, under(targ), iface.allTypes)
break
}
check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, under(targ), iface.allTypes)
return false
}
return check.subst(pos, typ, smap)
return true
}
// subst returns the type typ with its type parameters tpars replaced by