From 155dc0e541368bbd208bfcf12985f58fb375dd5c Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Fri, 21 May 2021 19:46:45 -0700 Subject: [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 Reviewed-by: Robert Findley --- src/cmd/compile/internal/types2/subst.go | 146 ++++++++++++++++--------------- 1 file changed, 77 insertions(+), 69 deletions(-) (limited to 'src/cmd/compile/internal/types2/subst.go') diff --git a/src/cmd/compile/internal/types2/subst.go b/src/cmd/compile/internal/types2/subst.go index 04a3527d6d..a2b81ba0cc 100644 --- a/src/cmd/compile/internal/types2/subst.go +++ b/src/cmd/compile/internal/types2/subst.go @@ -119,90 +119,98 @@ func (check *Checker) instantiate(pos syntax.Pos, typ Type, targs []Type, poslis // 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 -- cgit v1.2.3-54-g00ecf