// 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
+ }
+ }
- // 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
- check.completeInterface(nopos, iface)
- if len(iface.allMethods) > 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)
- break
- }
- 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)
- }
- 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 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
+ check.completeInterface(nopos, iface)
+ if len(iface.allMethods) > 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.allTypes == nil {
- continue // nothing to do
- }
+ // targ's underlying type must also be one of the interface types listed, if any
+ if iface.allTypes == 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.allTypes == nil {
- check.softErrorf(pos, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
- break
- }
- for _, t := range unpack(targBound.allTypes) {
- if !iface.isSatisfiedBy(t) {
- // 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, t, iface.allTypes)
- break
- }
+ // 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.allTypes == nil {
+ check.softErrorf(pos, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
+ return false
+ }
+ for _, t := range unpack(targBound.allTypes) {
+ if !iface.isSatisfiedBy(t) {
+ // 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, t, iface.allTypes)
+ 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(pos, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, under(targ), iface.allTypes)
- break
- }
+ // 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, 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