// (Cycles involving alias types, as in "type A = [10]A" are detected
// earlier, via the objDecl cycle detection mechanism.)
func (check *Checker) validType(typ *Named) {
- check.validType0(typ, nil, nil, nil)
+ check.validType0(typ, nil, nil)
}
// validType0 checks if the given type is valid. If typ is a type parameter
-// its value is looked up in the provided environment. The environment is
-// nil if typ is not part of (the RHS of) an instantiated type, in that case
-// any type parameter encountered must be from an enclosing function and can
-// be ignored. The nest list describes the stack (the "nest in memory") of
-// types which contain (or embed in the case of interfaces) other types. For
-// instance, a struct named S which contains a field of named type F contains
-// (the memory of) F in S, leading to the nest S->F. If a type appears in its
-// own nest (say S->F->S) we have an invalid recursive type. The path list is
-// the full path of named types in a cycle, it is only needed for error reporting.
-func (check *Checker) validType0(typ Type, env *tparamEnv, nest, path []*Named) bool {
+// its value is looked up in the type argument list of the instantiated
+// (enclosing) type, if it exists. Otherwise the type parameter must be from
+// an enclosing function and can be ignored.
+// The nest list describes the stack (the "nest in memory") of types which
+// contain (or embed in the case of interfaces) other types. For instance, a
+// struct named S which contains a field of named type F contains (the memory
+// of) F in S, leading to the nest S->F. If a type appears in its own nest
+// (say S->F->S) we have an invalid recursive type. The path list is the full
+// path of named types in a cycle, it is only needed for error reporting.
+func (check *Checker) validType0(typ Type, nest, path []*Named) bool {
switch t := typ.(type) {
case nil:
// We should never see a nil type but be conservative and panic
}
case *Array:
- return check.validType0(t.elem, env, nest, path)
+ return check.validType0(t.elem, nest, path)
case *Struct:
for _, f := range t.fields {
- if !check.validType0(f.typ, env, nest, path) {
+ if !check.validType0(f.typ, nest, path) {
return false
}
}
case *Union:
for _, t := range t.terms {
- if !check.validType0(t.typ, env, nest, path) {
+ if !check.validType0(t.typ, nest, path) {
return false
}
}
case *Interface:
for _, etyp := range t.embeddeds {
- if !check.validType0(etyp, env, nest, path) {
+ if !check.validType0(etyp, nest, path) {
return false
}
}
// Every type added to nest is also added to path; thus every type that is in nest
// must also be in path (invariant). But not every type in path is in nest, since
// nest may be pruned (see below, *TypeParam case).
- if !check.validType0(t.Origin().fromRHS, env.push(t), append(nest, t), append(path, t)) {
+ if !check.validType0(t.Origin().fromRHS, append(nest, t), append(path, t)) {
return false
}
case *TypeParam:
// A type parameter stands for the type (argument) it was instantiated with.
- // Check the corresponding type argument for validity if we have one.
- if env != nil {
- if targ := env.tmap[t]; targ != nil {
- // Type arguments found in targ must be looked
- // up in the enclosing environment env.link. The
- // type argument must be valid in the enclosing
- // type (where the current type was instantiated),
- // hence we must check targ's validity in the type
- // nest excluding the current (instantiated) type
- // (see the example at the end of this file).
- // For error reporting we keep the full path.
- return check.validType0(targ, env.link, nest[:len(nest)-1], path)
+ // Check the corresponding type argument for validity if we are in an
+ // instantiated type.
+ if len(nest) > 0 {
+ inst := nest[len(nest)-1] // the type instance
+ // Find the corresponding type argument for the type parameter
+ // and proceed with checking that type argument.
+ for i, tparam := range inst.TypeParams().list() {
+ // The type parameter and type argument lists should
+ // match in length but be careful in case of errors.
+ if t == tparam && i < inst.TypeArgs().Len() {
+ targ := inst.TypeArgs().At(i)
+ // The type argument must be valid in the enclosing
+ // type (where inst was instantiated), hence we must
+ // check targ's validity in the type nest excluding
+ // the current (instantiated) type (see the example
+ // at the end of this file).
+ // For error reporting we keep the full path.
+ return check.validType0(targ, nest[:len(nest)-1], path)
+ }
}
}
}
return olist
}
-// A tparamEnv provides the environment for looking up the type arguments
-// with which type parameters for a given instance were instantiated.
-// If we don't have an instance, the corresponding tparamEnv is nil.
-type tparamEnv struct {
- tmap substMap
- link *tparamEnv
-}
-
-func (env *tparamEnv) push(typ *Named) *tparamEnv {
- // If typ is not an instantiated type there are no typ-specific
- // type parameters to look up and we don't need an environment.
- targs := typ.TypeArgs()
- if targs == nil {
- return nil // no instance => nil environment
- }
-
- // Populate tmap: remember the type argument for each type parameter.
- // We cannot use makeSubstMap because the number of type parameters
- // and arguments may not match due to errors in the source (too many
- // or too few type arguments). Populate tmap "manually".
- tparams := typ.TypeParams()
- n, m := targs.Len(), tparams.Len()
- if n > m {
- n = m // too many targs
- }
- tmap := make(substMap, n)
- for i := 0; i < n; i++ {
- tmap[tparams.At(i)] = targs.At(i)
- }
-
- return &tparamEnv{tmap: tmap, link: env}
-}
-
-// TODO(gri) Alternative implementation:
-// We may not need to build a stack of environments to
-// look up the type arguments for type parameters. The
-// same information should be available via the path:
-// We should be able to just walk the path backwards
-// and find the type arguments in the instance objects.
-
// Here is an example illustrating why we need to exclude the
// instantiated type from nest when evaluating the validity of
// a type parameter. Given the declarations
// (Cycles involving alias types, as in "type A = [10]A" are detected
// earlier, via the objDecl cycle detection mechanism.)
func (check *Checker) validType(typ *Named) {
- check.validType0(typ, nil, nil, nil)
+ check.validType0(typ, nil, nil)
}
// validType0 checks if the given type is valid. If typ is a type parameter
-// its value is looked up in the provided environment. The environment is
-// nil if typ is not part of (the RHS of) an instantiated type, in that case
-// any type parameter encountered must be from an enclosing function and can
-// be ignored. The nest list describes the stack (the "nest in memory") of
-// types which contain (or embed in the case of interfaces) other types. For
-// instance, a struct named S which contains a field of named type F contains
-// (the memory of) F in S, leading to the nest S->F. If a type appears in its
-// own nest (say S->F->S) we have an invalid recursive type. The path list is
-// the full path of named types in a cycle, it is only needed for error reporting.
-func (check *Checker) validType0(typ Type, env *tparamEnv, nest, path []*Named) bool {
+// its value is looked up in the type argument list of the instantiated
+// (enclosing) type, if it exists. Otherwise the type parameter must be from
+// an enclosing function and can be ignored.
+// The nest list describes the stack (the "nest in memory") of types which
+// contain (or embed in the case of interfaces) other types. For instance, a
+// struct named S which contains a field of named type F contains (the memory
+// of) F in S, leading to the nest S->F. If a type appears in its own nest
+// (say S->F->S) we have an invalid recursive type. The path list is the full
+// path of named types in a cycle, it is only needed for error reporting.
+func (check *Checker) validType0(typ Type, nest, path []*Named) bool {
switch t := typ.(type) {
case nil:
// We should never see a nil type but be conservative and panic
}
case *Array:
- return check.validType0(t.elem, env, nest, path)
+ return check.validType0(t.elem, nest, path)
case *Struct:
for _, f := range t.fields {
- if !check.validType0(f.typ, env, nest, path) {
+ if !check.validType0(f.typ, nest, path) {
return false
}
}
case *Union:
for _, t := range t.terms {
- if !check.validType0(t.typ, env, nest, path) {
+ if !check.validType0(t.typ, nest, path) {
return false
}
}
case *Interface:
for _, etyp := range t.embeddeds {
- if !check.validType0(etyp, env, nest, path) {
+ if !check.validType0(etyp, nest, path) {
return false
}
}
// Every type added to nest is also added to path; thus every type that is in nest
// must also be in path (invariant). But not every type in path is in nest, since
// nest may be pruned (see below, *TypeParam case).
- if !check.validType0(t.Origin().fromRHS, env.push(t), append(nest, t), append(path, t)) {
+ if !check.validType0(t.Origin().fromRHS, append(nest, t), append(path, t)) {
return false
}
case *TypeParam:
// A type parameter stands for the type (argument) it was instantiated with.
- // Check the corresponding type argument for validity if we have one.
- if env != nil {
- if targ := env.tmap[t]; targ != nil {
- // Type arguments found in targ must be looked
- // up in the enclosing environment env.link. The
- // type argument must be valid in the enclosing
- // type (where the current type was instantiated),
- // hence we must check targ's validity in the type
- // nest excluding the current (instantiated) type
- // (see the example at the end of this file).
- // For error reporting we keep the full path.
- return check.validType0(targ, env.link, nest[:len(nest)-1], path)
+ // Check the corresponding type argument for validity if we are in an
+ // instantiated type.
+ if len(nest) > 0 {
+ inst := nest[len(nest)-1] // the type instance
+ // Find the corresponding type argument for the type parameter
+ // and proceed with checking that type argument.
+ for i, tparam := range inst.TypeParams().list() {
+ // The type parameter and type argument lists should
+ // match in length but be careful in case of errors.
+ if t == tparam && i < inst.TypeArgs().Len() {
+ targ := inst.TypeArgs().At(i)
+ // The type argument must be valid in the enclosing
+ // type (where inst was instantiated), hence we must
+ // check targ's validity in the type nest excluding
+ // the current (instantiated) type (see the example
+ // at the end of this file).
+ // For error reporting we keep the full path.
+ return check.validType0(targ, nest[:len(nest)-1], path)
+ }
}
}
}
return olist
}
-// A tparamEnv provides the environment for looking up the type arguments
-// with which type parameters for a given instance were instantiated.
-// If we don't have an instance, the corresponding tparamEnv is nil.
-type tparamEnv struct {
- tmap substMap
- link *tparamEnv
-}
-
-func (env *tparamEnv) push(typ *Named) *tparamEnv {
- // If typ is not an instantiated type there are no typ-specific
- // type parameters to look up and we don't need an environment.
- targs := typ.TypeArgs()
- if targs == nil {
- return nil // no instance => nil environment
- }
-
- // Populate tmap: remember the type argument for each type parameter.
- // We cannot use makeSubstMap because the number of type parameters
- // and arguments may not match due to errors in the source (too many
- // or too few type arguments). Populate tmap "manually".
- tparams := typ.TypeParams()
- n, m := targs.Len(), tparams.Len()
- if n > m {
- n = m // too many targs
- }
- tmap := make(substMap, n)
- for i := 0; i < n; i++ {
- tmap[tparams.At(i)] = targs.At(i)
- }
-
- return &tparamEnv{tmap: tmap, link: env}
-}
-
-// TODO(gri) Alternative implementation:
-// We may not need to build a stack of environments to
-// look up the type arguments for type parameters. The
-// same information should be available via the path:
-// We should be able to just walk the path backwards
-// and find the type arguments in the instance objects.
-
// Here is an example illustrating why we need to exclude the
// instantiated type from nest when evaluating the validity of
// a type parameter. Given the declarations