1 // Copyright 2014 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
9 "cmd/compile/internal/syntax"
12 . "internal/types/errors"
15 func (err *error_) recordAltDecl(obj Object) {
16 if pos := obj.Pos(); pos.IsKnown() {
17 // We use "other" rather than "previous" here because
18 // the first declaration seen may not be textually
19 // earlier in the source.
20 err.errorf(pos, "other declaration of %s", obj.Name())
24 func (check *Checker) declare(scope *Scope, id *syntax.Name, obj Object, pos syntax.Pos) {
25 // spec: "The blank identifier, represented by the underscore
26 // character _, may be used in a declaration like any other
27 // identifier but the declaration does not introduce a new
29 if obj.Name() != "_" {
30 if alt := scope.Insert(obj); alt != nil {
32 err.code = DuplicateDecl
33 err.errorf(obj, "%s redeclared in this block", obj.Name())
34 err.recordAltDecl(alt)
41 check.recordDef(id, obj)
45 // pathString returns a string of the form a->b-> ... ->g for a path [a, b, ... g].
46 func pathString(path []Object) string {
48 for i, p := range path {
57 // objDecl type-checks the declaration of obj in its respective (file) environment.
58 // For the meaning of def, see Checker.definedType, in typexpr.go.
59 func (check *Checker) objDecl(obj Object, def *Named) {
60 if check.conf.Trace && obj.Type() == nil {
61 if check.indent == 0 {
62 fmt.Println() // empty line between top-level objects for readability
64 check.trace(obj.Pos(), "-- checking %s (%s, objPath = %s)", obj, obj.color(), pathString(check.objPath))
68 check.trace(obj.Pos(), "=> %s (%s)", obj, obj.color())
72 // Checking the declaration of obj means inferring its type
73 // (and possibly its value, for constants).
74 // An object's type (and thus the object) may be in one of
75 // three states which are expressed by colors:
77 // - an object whose type is not yet known is painted white (initial color)
78 // - an object whose type is in the process of being inferred is painted grey
79 // - an object whose type is fully inferred is painted black
81 // During type inference, an object's color changes from white to grey
82 // to black (pre-declared objects are painted black from the start).
83 // A black object (i.e., its type) can only depend on (refer to) other black
84 // ones. White and grey objects may depend on white and black objects.
85 // A dependency on a grey object indicates a cycle which may or may not be
88 // When objects turn grey, they are pushed on the object path (a stack);
89 // they are popped again when they turn black. Thus, if a grey object (a
90 // cycle) is encountered, it is on the object path, and all the objects
91 // it depends on are the remaining objects on that path. Color encoding
92 // is such that the color value of a grey object indicates the index of
93 // that object in the object path.
95 // During type-checking, white objects may be assigned a type without
96 // traversing through objDecl; e.g., when initializing constants and
97 // variables. Update the colors of those objects here (rather than
98 // everywhere where we set the type) to satisfy the color invariants.
99 if obj.color() == white && obj.Type() != nil {
106 assert(obj.Type() == nil)
107 // All color values other than white and black are considered grey.
108 // Because black and white are < grey, all values >= grey are grey.
109 // Use those values to encode the object's index into the object path.
110 obj.setColor(grey + color(check.push(obj)))
112 check.pop().setColor(black)
116 assert(obj.Type() != nil)
120 // Color values other than white or black are considered grey.
124 // We have a (possibly invalid) cycle.
125 // In the existing code, this is marked by a non-nil type
126 // for the object except for constants and variables whose
127 // type may be non-nil (known), or nil if it depends on the
128 // not-yet known initialization value.
129 // In the former case, set the type to Typ[Invalid] because
130 // we have an initialization cycle. The cycle error will be
131 // reported later, when determining initialization order.
132 // TODO(gri) Report cycle here and simplify initialization
134 switch obj := obj.(type) {
136 if !check.validCycle(obj) || obj.typ == nil {
137 obj.typ = Typ[Invalid]
141 if !check.validCycle(obj) || obj.typ == nil {
142 obj.typ = Typ[Invalid]
146 if !check.validCycle(obj) {
148 // (without this, calling underlying()
149 // below may lead to an endless loop
150 // if we have a cycle for a defined
152 obj.typ = Typ[Invalid]
156 if !check.validCycle(obj) {
157 // Don't set obj.typ to Typ[Invalid] here
158 // because plenty of code type-asserts that
159 // functions have a *Signature type. Grey
160 // functions have their type set to an empty
161 // signature which makes it impossible to
162 // initialize a variable with the function.
168 assert(obj.Type() != nil)
172 d := check.objMap[obj]
174 check.dump("%v: %s should have been declared", obj.Pos(), obj)
178 // save/restore current environment and set up object environment
179 defer func(env environment) {
180 check.environment = env
182 check.environment = environment{
186 // Const and var declarations must not have initialization
187 // cycles. We track them by remembering the current declaration
188 // in check.decl. Initialization expressions depending on other
189 // consts, vars, or functions, add dependencies to the current
191 switch obj := obj.(type) {
193 check.decl = d // new package-level const decl
194 check.constDecl(obj, d.vtyp, d.init, d.inherited)
196 check.decl = d // new package-level var decl
197 check.varDecl(obj, d.lhs, d.vtyp, d.init)
199 // invalid recursive types are detected via path
200 check.typeDecl(obj, d.tdecl, def)
201 check.collectMethods(obj) // methods can only be added to top-level types
203 // functions may be recursive - no need to track dependencies
204 check.funcDecl(obj, d)
210 // validCycle reports whether the cycle starting with obj is valid and
211 // reports an error if it is not.
212 func (check *Checker) validCycle(obj Object) (valid bool) {
213 // The object map contains the package scope objects and the non-interface methods.
215 info := check.objMap[obj]
216 inObjMap := info != nil && (info.fdecl == nil || info.fdecl.Recv == nil) // exclude methods
217 isPkgObj := obj.Parent() == check.pkg.scope
218 if isPkgObj != inObjMap {
219 check.dump("%v: inconsistent object map for %s (isPkgObj = %v, inObjMap = %v)", obj.Pos(), obj, isPkgObj, inObjMap)
224 // Count cycle objects.
225 assert(obj.color() >= grey)
226 start := obj.color() - grey // index of obj in objPath
227 cycle := check.objPath[start:]
228 tparCycle := false // if set, the cycle is through a type parameter list
229 nval := 0 // number of (constant or variable) values in the cycle; valid if !generic
230 ndef := 0 // number of type definitions in the cycle; valid if !generic
232 for _, obj := range cycle {
233 switch obj := obj.(type) {
237 // If we reach a generic type that is part of a cycle
238 // and we are in a type parameter list, we have a cycle
239 // through a type parameter list, which is invalid.
240 if check.inTParamList && isGeneric(obj.typ) {
245 // Determine if the type name is an alias or not. For
246 // package-level objects, use the object map which
247 // provides syntactic information (which doesn't rely
248 // on the order in which the objects are set up). For
249 // local objects, we can rely on the order, so use
250 // the object's predicate.
251 // TODO(gri) It would be less fragile to always access
252 // the syntactic information. We should consider storing
253 // this information explicitly in the object.
255 if d := check.objMap[obj]; d != nil {
256 alias = d.tdecl.Alias // package-level object
258 alias = obj.IsAlias() // function local object
270 if check.conf.Trace {
271 check.trace(obj.Pos(), "## cycle detected: objPath = %s->%s (len = %d)", pathString(cycle), obj.Name(), len(cycle))
273 check.trace(obj.Pos(), "## cycle contains: generic type in a type parameter list")
275 check.trace(obj.Pos(), "## cycle contains: %d values, %d type definitions", nval, ndef)
279 check.trace(obj.Pos(), "=> cycle is valid")
281 check.trace(obj.Pos(), "=> error: cycle is invalid")
287 // A cycle involving only constants and variables is invalid but we
288 // ignore them here because they are reported via the initialization
290 if nval == len(cycle) {
294 // A cycle involving only types (and possibly functions) must have at least
295 // one type definition to be permitted: If there is no type definition, we
296 // have a sequence of alias type names which will expand ad infinitum.
297 if nval == 0 && ndef > 0 {
302 check.cycleError(cycle)
306 // cycleError reports a declaration cycle starting with
307 // the object in cycle that is "first" in the source.
308 func (check *Checker) cycleError(cycle []Object) {
309 // name returns the (possibly qualified) object name.
310 // This is needed because with generic types, cycles
311 // may refer to imported types. See issue #50788.
312 // TODO(gri) This functionality is used elsewhere. Factor it out.
313 name := func(obj Object) string {
315 writePackage(&buf, obj.Pkg(), check.qualifier)
316 buf.WriteString(obj.Name())
320 // TODO(gri) Should we start with the last (rather than the first) object in the cycle
321 // since that is the earliest point in the source where we start seeing the
322 // cycle? That would be more consistent with other error messages.
323 i := firstInSrc(cycle)
326 // If obj is a type alias, mark it as valid (not broken) in order to avoid follow-on errors.
327 tname, _ := obj.(*TypeName)
328 if tname != nil && tname.IsAlias() {
329 check.validAlias(tname, Typ[Invalid])
332 // report a more concise error for self references
335 check.errorf(obj, InvalidDeclCycle, "invalid recursive type: %s refers to itself", objName)
337 check.errorf(obj, InvalidDeclCycle, "invalid cycle in declaration: %s refers to itself", objName)
343 err.code = InvalidDeclCycle
345 err.errorf(obj, "invalid recursive type %s", objName)
347 err.errorf(obj, "invalid cycle in declaration of %s", objName)
350 err.errorf(obj, "%s refers to", objName)
358 err.errorf(obj, "%s", objName)
362 // firstInSrc reports the index of the object with the "smallest"
363 // source position in path. path must not be empty.
364 func firstInSrc(path []Object) int {
365 fst, pos := 0, path[0].Pos()
366 for i, t := range path[1:] {
367 if t.Pos().Cmp(pos) < 0 {
368 fst, pos = i+1, t.Pos()
374 func (check *Checker) constDecl(obj *Const, typ, init syntax.Expr, inherited bool) {
375 assert(obj.typ == nil)
377 // use the correct value of iota and errpos
378 defer func(iota constant.Value, errpos syntax.Pos) {
380 check.errpos = errpos
381 }(check.iota, check.errpos)
385 // provide valid constant value under all circumstances
386 obj.val = constant.MakeUnknown()
388 // determine type, if any
392 // don't report an error if the type is an invalid C (defined) type
394 if under(t) != Typ[Invalid] {
395 check.errorf(typ, InvalidConstType, "invalid constant type %s", t)
397 obj.typ = Typ[Invalid]
403 // check initialization
407 // The initialization expression is inherited from a previous
408 // constant declaration, and (error) positions refer to that
409 // expression and not the current constant declaration. Use
410 // the constant identifier position for any errors during
411 // init expression evaluation since that is all we have
412 // (see issues #42991, #42992).
413 check.errpos = obj.pos
417 check.initConst(obj, &x)
420 func (check *Checker) varDecl(obj *Var, lhs []*Var, typ, init syntax.Expr) {
421 assert(obj.typ == nil)
423 // If we have undefined variable types due to errors,
424 // mark variables as used to avoid follow-on errors.
425 // Matches compiler behavior.
427 if obj.typ == Typ[Invalid] {
430 for _, lhs := range lhs {
431 if lhs.typ == Typ[Invalid] {
437 // determine type, if any
439 obj.typ = check.varType(typ)
440 // We cannot spread the type to all lhs variables if there
441 // are more than one since that would mark them as checked
442 // (see Checker.objDecl) and the assignment of init exprs,
443 // if any, would not be checked.
445 // TODO(gri) If we have no init expr, we should distribute
446 // a given type otherwise we need to re-evalate the type
447 // expr for each lhs variable, leading to duplicate work.
450 // check initialization
453 // error reported before by arityMatch
454 obj.typ = Typ[Invalid]
459 if lhs == nil || len(lhs) == 1 {
460 assert(lhs == nil || lhs[0] == obj)
463 check.initVar(obj, &x, "variable declaration")
468 // obj must be one of lhs
470 for _, lhs := range lhs {
477 panic("inconsistent lhs")
481 // We have multiple variables on the lhs and one init expr.
482 // Make sure all variables have been given the same type if
483 // one was specified, otherwise they assume the type of the
484 // init expression values (was issue #15755).
486 for _, lhs := range lhs {
491 check.initVars(lhs, []syntax.Expr{init}, nil)
494 // isImportedConstraint reports whether typ is an imported type constraint.
495 func (check *Checker) isImportedConstraint(typ Type) bool {
496 named, _ := typ.(*Named)
497 if named == nil || named.obj.pkg == check.pkg || named.obj.pkg == nil {
500 u, _ := named.under().(*Interface)
501 return u != nil && !u.IsMethodSet()
504 func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *Named) {
505 assert(obj.typ == nil)
509 if t, _ := obj.typ.(*Named); t != nil { // type may be invalid
512 // If typ is local, an error was already reported where typ is specified/defined.
513 if check.isImportedConstraint(rhs) && !check.allowVersion(check.pkg, 1, 18) {
514 check.versionErrorf(tdecl.Type, "go1.18", "using type constraint %s", rhs)
516 }).describef(obj, "validType(%s)", obj.Name())
519 if alias && tdecl.TParamList != nil {
520 // The parser will ensure this but we may still get an invalid AST.
521 // Complain and continue as regular type definition.
522 check.error(tdecl, BadDecl, "generic type cannot be alias")
528 if !check.allowVersion(check.pkg, 1, 9) {
529 check.versionErrorf(tdecl, "go1.9", "type aliases")
532 check.brokenAlias(obj)
533 rhs = check.typ(tdecl.Type)
534 check.validAlias(obj, rhs)
538 // type definition or generic type declaration
539 named := check.newNamed(obj, nil, nil)
540 def.setUnderlying(named)
542 if tdecl.TParamList != nil {
543 check.openScope(tdecl, "type parameters")
544 defer check.closeScope()
545 check.collectTypeParams(&named.tparams, tdecl.TParamList)
548 // determine underlying type of named
549 rhs = check.definedType(tdecl.Type, named)
553 // If the underlying type was not set while type-checking the right-hand
554 // side, it is invalid and an error should have been reported elsewhere.
555 if named.underlying == nil {
556 named.underlying = Typ[Invalid]
559 // Disallow a lone type parameter as the RHS of a type declaration (issue #45639).
560 // We don't need this restriction anymore if we make the underlying type of a type
561 // parameter its constraint interface: if the RHS is a lone type parameter, we will
562 // use its underlying type (like we do for any RHS in a type declaration), and its
563 // underlying type is an interface and the type declaration is well defined.
564 if isTypeParam(rhs) {
565 check.error(tdecl.Type, MisplacedTypeParam, "cannot use a type parameter as RHS in type declaration")
566 named.underlying = Typ[Invalid]
570 func (check *Checker) collectTypeParams(dst **TypeParamList, list []*syntax.Field) {
571 tparams := make([]*TypeParam, len(list))
573 // Declare type parameters up-front.
574 // The scope of type parameters starts at the beginning of the type parameter
575 // list (so we can have mutually recursive parameterized type bounds).
576 for i, f := range list {
577 tparams[i] = check.declareTypeParam(f.Name)
580 // Set the type parameters before collecting the type constraints because
581 // the parameterized type may be used by the constraints (issue #47887).
582 // Example: type T[P T[P]] interface{}
583 *dst = bindTParams(tparams)
585 // Signal to cycle detection that we are in a type parameter list.
586 // We can only be inside one type parameter list at any given time:
587 // function closures may appear inside a type parameter list but they
588 // cannot be generic, and their bodies are processed in delayed and
589 // sequential fashion. Note that with each new declaration, we save
590 // the existing environment and restore it when done; thus inTParamList
591 // is true exactly only when we are in a specific type parameter list.
592 assert(!check.inTParamList)
593 check.inTParamList = true
595 check.inTParamList = false
598 // Keep track of bounds for later validation.
600 for i, f := range list {
601 // Optimization: Re-use the previous type bound if it hasn't changed.
602 // This also preserves the grouped output of type parameter lists
603 // when printing type strings.
604 if i == 0 || f.Type != list[i-1].Type {
605 bound = check.bound(f.Type)
606 if isTypeParam(bound) {
607 // We may be able to allow this since it is now well-defined what
608 // the underlying type and thus type set of a type parameter is.
609 // But we may need some additional form of cycle detection within
610 // type parameter lists.
611 check.error(f.Type, MisplacedTypeParam, "cannot use a type parameter as constraint")
615 tparams[i].bound = bound
619 func (check *Checker) bound(x syntax.Expr) Type {
620 // A type set literal of the form ~T and A|B may only appear as constraint;
621 // embed it in an implicit interface so that only interface type-checking
622 // needs to take care of such type expressions.
623 if op, _ := x.(*syntax.Operation); op != nil && (op.Op == syntax.Tilde || op.Op == syntax.Or) {
624 t := check.typ(&syntax.InterfaceType{MethodList: []*syntax.Field{{Type: x}}})
625 // mark t as implicit interface if all went well
626 if t, _ := t.(*Interface); t != nil {
634 func (check *Checker) declareTypeParam(name *syntax.Name) *TypeParam {
635 // Use Typ[Invalid] for the type constraint to ensure that a type
636 // is present even if the actual constraint has not been assigned
638 // TODO(gri) Need to systematically review all uses of type parameter
639 // constraints to make sure we don't rely on them if they
640 // are not properly set yet.
641 tname := NewTypeName(name.Pos(), check.pkg, name.Value, nil)
642 tpar := check.newTypeParam(tname, Typ[Invalid]) // assigns type to tname as a side-effect
643 check.declare(check.scope, name, tname, check.scope.pos) // TODO(gri) check scope position
647 func (check *Checker) collectMethods(obj *TypeName) {
648 // get associated methods
649 // (Checker.collectObjects only collects methods with non-blank names;
650 // Checker.resolveBaseTypeName ensures that obj is not an alias name
651 // if it has attached methods.)
652 methods := check.methods[obj]
656 delete(check.methods, obj)
657 assert(!check.objMap[obj].tdecl.Alias) // don't use TypeName.IsAlias (requires fully set up object)
659 // use an objset to check for name conflicts
662 // spec: "If the base type is a struct type, the non-blank method
663 // and field names must be distinct."
664 base, _ := obj.typ.(*Named) // shouldn't fail but be conservative
666 assert(base.TypeArgs().Len() == 0) // collectMethods should not be called on an instantiated type
668 // See issue #52529: we must delay the expansion of underlying here, as
669 // base may not be fully set-up.
671 check.checkFieldUniqueness(base)
672 }).describef(obj, "verifying field uniqueness for %v", base)
674 // Checker.Files may be called multiple times; additional package files
675 // may add methods to already type-checked types. Add pre-existing methods
676 // so that we can detect redeclarations.
677 for i := 0; i < base.NumMethods(); i++ {
679 assert(m.name != "_")
680 assert(mset.insert(m) == nil)
685 for _, m := range methods {
686 // spec: "For a base type, the non-blank names of methods bound
687 // to it must be unique."
688 assert(m.name != "_")
689 if alt := mset.insert(m); alt != nil {
690 if alt.Pos().IsKnown() {
691 check.errorf(m.pos, DuplicateMethod, "method %s.%s already declared at %s", obj.Name(), m.name, alt.Pos())
693 check.errorf(m.pos, DuplicateMethod, "method %s.%s already declared", obj.Name(), m.name)
704 func (check *Checker) checkFieldUniqueness(base *Named) {
705 if t, _ := base.under().(*Struct); t != nil {
707 for i := 0; i < base.NumMethods(); i++ {
709 assert(m.name != "_")
710 assert(mset.insert(m) == nil)
713 // Check that any non-blank field names of base are distinct from its
715 for _, fld := range t.fields {
717 if alt := mset.insert(fld); alt != nil {
718 // Struct fields should already be unique, so we should only
719 // encounter an alternate via collision with a method name.
722 // For historical consistency, we report the primary error on the
723 // method, and the alt decl on the field.
725 err.code = DuplicateFieldAndMethod
726 err.errorf(alt, "field and method with the same name %s", fld.name)
727 err.recordAltDecl(fld)
735 func (check *Checker) funcDecl(obj *Func, decl *declInfo) {
736 assert(obj.typ == nil)
738 // func declarations cannot use iota
739 assert(check.iota == nil)
741 sig := new(Signature)
742 obj.typ = sig // guard against cycles
744 // Avoid cycle error when referring to method while type-checking the signature.
745 // This avoids a nuisance in the best case (non-parameterized receiver type) and
746 // since the method is not a type, we get an error. If we have a parameterized
747 // receiver type, instantiating the receiver type leads to the instantiation of
748 // its methods, and we don't want a cycle error in that case.
749 // TODO(gri) review if this is correct and/or whether we still need this?
753 check.funcType(sig, fdecl.Recv, fdecl.TParamList, fdecl.Type)
756 if len(fdecl.TParamList) > 0 && fdecl.Body == nil {
757 check.softErrorf(fdecl, BadDecl, "generic function is missing function body")
760 // function body must be type-checked after global declarations
761 // (functions implemented elsewhere have no body)
762 if !check.conf.IgnoreFuncBodies && fdecl.Body != nil {
764 check.funcBody(decl, obj.name, sig, fdecl.Body, nil)
765 }).describef(obj, "func %s", obj.name)
769 func (check *Checker) declStmt(list []syntax.Decl) {
772 first := -1 // index of first ConstDecl in the current group, or -1
773 var last *syntax.ConstDecl // last ConstDecl with init expressions, or nil
774 for index, decl := range list {
775 if _, ok := decl.(*syntax.ConstDecl); !ok {
776 first = -1 // we're not in a constant declaration
779 switch s := decl.(type) {
780 case *syntax.ConstDecl:
781 top := len(check.delayed)
783 // iota is the index of the current constDecl within the group
784 if first < 0 || s.Group == nil || list[index-1].(*syntax.ConstDecl).Group != s.Group {
788 iota := constant.MakeInt64(int64(index - first))
790 // determine which initialization expressions to use
793 case s.Type != nil || s.Values != nil:
797 last = new(syntax.ConstDecl) // make sure last exists
801 // declare all constants
802 lhs := make([]*Const, len(s.NameList))
803 values := unpackExpr(last.Values)
804 for i, name := range s.NameList {
805 obj := NewConst(name.Pos(), pkg, name.Value, nil, iota)
813 check.constDecl(obj, last.Type, init, inherited)
816 // Constants must always have init values.
817 check.arity(s.Pos(), s.NameList, values, true, inherited)
819 // process function literals in init expressions before scope changes
820 check.processDelayed(top)
822 // spec: "The scope of a constant or variable identifier declared
823 // inside a function begins at the end of the ConstSpec or VarSpec
824 // (ShortVarDecl for short variable declarations) and ends at the
825 // end of the innermost containing block."
826 scopePos := syntax.EndPos(s)
827 for i, name := range s.NameList {
828 check.declare(check.scope, name, lhs[i], scopePos)
831 case *syntax.VarDecl:
832 top := len(check.delayed)
834 lhs0 := make([]*Var, len(s.NameList))
835 for i, name := range s.NameList {
836 lhs0[i] = NewVar(name.Pos(), pkg, name.Value, nil)
839 // initialize all variables
840 values := unpackExpr(s.Values)
841 for i, obj := range lhs0 {
845 case len(s.NameList):
849 // rhs is expected to be a multi-valued expression
857 check.varDecl(obj, lhs, s.Type, init)
858 if len(values) == 1 {
859 // If we have a single lhs variable we are done either way.
860 // If we have a single rhs expression, it must be a multi-
861 // valued expression, in which case handling the first lhs
862 // variable will cause all lhs variables to have a type
863 // assigned, and we are done as well.
865 for _, obj := range lhs0 {
866 assert(obj.typ != nil)
873 // If we have no type, we must have values.
874 if s.Type == nil || values != nil {
875 check.arity(s.Pos(), s.NameList, values, false, false)
878 // process function literals in init expressions before scope changes
879 check.processDelayed(top)
881 // declare all variables
882 // (only at this point are the variable scopes (parents) set)
883 scopePos := syntax.EndPos(s) // see constant declarations
884 for i, name := range s.NameList {
885 // see constant declarations
886 check.declare(check.scope, name, lhs0[i], scopePos)
889 case *syntax.TypeDecl:
890 obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Value, nil)
891 // spec: "The scope of a type identifier declared inside a function
892 // begins at the identifier in the TypeSpec and ends at the end of
893 // the innermost containing block."
894 scopePos := s.Name.Pos()
895 check.declare(check.scope, s.Name, obj, scopePos)
896 // mark and unmark type before calling typeDecl; its type is still nil (see Checker.objDecl)
897 obj.setColor(grey + color(check.push(obj)))
898 check.typeDecl(obj, s, nil)
899 check.pop().setColor(black)
902 check.errorf(s, InvalidSyntaxTree, invalidAST+"unknown syntax.Decl node %T", s)