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-rw-r--r--src/go/parser/resolver.go612
1 files changed, 612 insertions, 0 deletions
diff --git a/src/go/parser/resolver.go b/src/go/parser/resolver.go
new file mode 100644
index 0000000..f8ff618
--- /dev/null
+++ b/src/go/parser/resolver.go
@@ -0,0 +1,612 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package parser
+
+import (
+ "fmt"
+ "go/ast"
+ "go/token"
+ "strings"
+)
+
+const debugResolve = false
+
+// resolveFile walks the given file to resolve identifiers within the file
+// scope, updating ast.Ident.Obj fields with declaration information.
+//
+// If declErr is non-nil, it is used to report declaration errors during
+// resolution. tok is used to format position in error messages.
+func resolveFile(file *ast.File, handle *token.File, declErr func(token.Pos, string)) {
+ pkgScope := ast.NewScope(nil)
+ r := &resolver{
+ handle: handle,
+ declErr: declErr,
+ topScope: pkgScope,
+ pkgScope: pkgScope,
+ depth: 1,
+ }
+
+ for _, decl := range file.Decls {
+ ast.Walk(r, decl)
+ }
+
+ r.closeScope()
+ assert(r.topScope == nil, "unbalanced scopes")
+ assert(r.labelScope == nil, "unbalanced label scopes")
+
+ // resolve global identifiers within the same file
+ i := 0
+ for _, ident := range r.unresolved {
+ // i <= index for current ident
+ assert(ident.Obj == unresolved, "object already resolved")
+ ident.Obj = r.pkgScope.Lookup(ident.Name) // also removes unresolved sentinel
+ if ident.Obj == nil {
+ r.unresolved[i] = ident
+ i++
+ } else if debugResolve {
+ pos := ident.Obj.Decl.(interface{ Pos() token.Pos }).Pos()
+ r.trace("resolved %s@%v to package object %v", ident.Name, ident.Pos(), pos)
+ }
+ }
+ file.Scope = r.pkgScope
+ file.Unresolved = r.unresolved[0:i]
+}
+
+const maxScopeDepth int = 1e3
+
+type resolver struct {
+ handle *token.File
+ declErr func(token.Pos, string)
+
+ // Ordinary identifier scopes
+ pkgScope *ast.Scope // pkgScope.Outer == nil
+ topScope *ast.Scope // top-most scope; may be pkgScope
+ unresolved []*ast.Ident // unresolved identifiers
+ depth int // scope depth
+
+ // Label scopes
+ // (maintained by open/close LabelScope)
+ labelScope *ast.Scope // label scope for current function
+ targetStack [][]*ast.Ident // stack of unresolved labels
+}
+
+func (r *resolver) trace(format string, args ...any) {
+ fmt.Println(strings.Repeat(". ", r.depth) + r.sprintf(format, args...))
+}
+
+func (r *resolver) sprintf(format string, args ...any) string {
+ for i, arg := range args {
+ switch arg := arg.(type) {
+ case token.Pos:
+ args[i] = r.handle.Position(arg)
+ }
+ }
+ return fmt.Sprintf(format, args...)
+}
+
+func (r *resolver) openScope(pos token.Pos) {
+ r.depth++
+ if r.depth > maxScopeDepth {
+ panic(bailout{pos: pos, msg: "exceeded max scope depth during object resolution"})
+ }
+ if debugResolve {
+ r.trace("opening scope @%v", pos)
+ }
+ r.topScope = ast.NewScope(r.topScope)
+}
+
+func (r *resolver) closeScope() {
+ r.depth--
+ if debugResolve {
+ r.trace("closing scope")
+ }
+ r.topScope = r.topScope.Outer
+}
+
+func (r *resolver) openLabelScope() {
+ r.labelScope = ast.NewScope(r.labelScope)
+ r.targetStack = append(r.targetStack, nil)
+}
+
+func (r *resolver) closeLabelScope() {
+ // resolve labels
+ n := len(r.targetStack) - 1
+ scope := r.labelScope
+ for _, ident := range r.targetStack[n] {
+ ident.Obj = scope.Lookup(ident.Name)
+ if ident.Obj == nil && r.declErr != nil {
+ r.declErr(ident.Pos(), fmt.Sprintf("label %s undefined", ident.Name))
+ }
+ }
+ // pop label scope
+ r.targetStack = r.targetStack[0:n]
+ r.labelScope = r.labelScope.Outer
+}
+
+func (r *resolver) declare(decl, data any, scope *ast.Scope, kind ast.ObjKind, idents ...*ast.Ident) {
+ for _, ident := range idents {
+ if ident.Obj != nil {
+ panic(fmt.Sprintf("%v: identifier %s already declared or resolved", ident.Pos(), ident.Name))
+ }
+ obj := ast.NewObj(kind, ident.Name)
+ // remember the corresponding declaration for redeclaration
+ // errors and global variable resolution/typechecking phase
+ obj.Decl = decl
+ obj.Data = data
+ // Identifiers (for receiver type parameters) are written to the scope, but
+ // never set as the resolved object. See issue #50956.
+ if _, ok := decl.(*ast.Ident); !ok {
+ ident.Obj = obj
+ }
+ if ident.Name != "_" {
+ if debugResolve {
+ r.trace("declaring %s@%v", ident.Name, ident.Pos())
+ }
+ if alt := scope.Insert(obj); alt != nil && r.declErr != nil {
+ prevDecl := ""
+ if pos := alt.Pos(); pos.IsValid() {
+ prevDecl = r.sprintf("\n\tprevious declaration at %v", pos)
+ }
+ r.declErr(ident.Pos(), fmt.Sprintf("%s redeclared in this block%s", ident.Name, prevDecl))
+ }
+ }
+ }
+}
+
+func (r *resolver) shortVarDecl(decl *ast.AssignStmt) {
+ // Go spec: A short variable declaration may redeclare variables
+ // provided they were originally declared in the same block with
+ // the same type, and at least one of the non-blank variables is new.
+ n := 0 // number of new variables
+ for _, x := range decl.Lhs {
+ if ident, isIdent := x.(*ast.Ident); isIdent {
+ assert(ident.Obj == nil, "identifier already declared or resolved")
+ obj := ast.NewObj(ast.Var, ident.Name)
+ // remember corresponding assignment for other tools
+ obj.Decl = decl
+ ident.Obj = obj
+ if ident.Name != "_" {
+ if debugResolve {
+ r.trace("declaring %s@%v", ident.Name, ident.Pos())
+ }
+ if alt := r.topScope.Insert(obj); alt != nil {
+ ident.Obj = alt // redeclaration
+ } else {
+ n++ // new declaration
+ }
+ }
+ }
+ }
+ if n == 0 && r.declErr != nil {
+ r.declErr(decl.Lhs[0].Pos(), "no new variables on left side of :=")
+ }
+}
+
+// The unresolved object is a sentinel to mark identifiers that have been added
+// to the list of unresolved identifiers. The sentinel is only used for verifying
+// internal consistency.
+var unresolved = new(ast.Object)
+
+// If x is an identifier, resolve attempts to resolve x by looking up
+// the object it denotes. If no object is found and collectUnresolved is
+// set, x is marked as unresolved and collected in the list of unresolved
+// identifiers.
+func (r *resolver) resolve(ident *ast.Ident, collectUnresolved bool) {
+ if ident.Obj != nil {
+ panic(r.sprintf("%v: identifier %s already declared or resolved", ident.Pos(), ident.Name))
+ }
+ // '_' should never refer to existing declarations, because it has special
+ // handling in the spec.
+ if ident.Name == "_" {
+ return
+ }
+ for s := r.topScope; s != nil; s = s.Outer {
+ if obj := s.Lookup(ident.Name); obj != nil {
+ if debugResolve {
+ r.trace("resolved %v:%s to %v", ident.Pos(), ident.Name, obj)
+ }
+ assert(obj.Name != "", "obj with no name")
+ // Identifiers (for receiver type parameters) are written to the scope,
+ // but never set as the resolved object. See issue #50956.
+ if _, ok := obj.Decl.(*ast.Ident); !ok {
+ ident.Obj = obj
+ }
+ return
+ }
+ }
+ // all local scopes are known, so any unresolved identifier
+ // must be found either in the file scope, package scope
+ // (perhaps in another file), or universe scope --- collect
+ // them so that they can be resolved later
+ if collectUnresolved {
+ ident.Obj = unresolved
+ r.unresolved = append(r.unresolved, ident)
+ }
+}
+
+func (r *resolver) walkExprs(list []ast.Expr) {
+ for _, node := range list {
+ ast.Walk(r, node)
+ }
+}
+
+func (r *resolver) walkLHS(list []ast.Expr) {
+ for _, expr := range list {
+ expr := unparen(expr)
+ if _, ok := expr.(*ast.Ident); !ok && expr != nil {
+ ast.Walk(r, expr)
+ }
+ }
+}
+
+func (r *resolver) walkStmts(list []ast.Stmt) {
+ for _, stmt := range list {
+ ast.Walk(r, stmt)
+ }
+}
+
+func (r *resolver) Visit(node ast.Node) ast.Visitor {
+ if debugResolve && node != nil {
+ r.trace("node %T@%v", node, node.Pos())
+ }
+
+ switch n := node.(type) {
+
+ // Expressions.
+ case *ast.Ident:
+ r.resolve(n, true)
+
+ case *ast.FuncLit:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ r.walkFuncType(n.Type)
+ r.walkBody(n.Body)
+
+ case *ast.SelectorExpr:
+ ast.Walk(r, n.X)
+ // Note: don't try to resolve n.Sel, as we don't support qualified
+ // resolution.
+
+ case *ast.StructType:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ r.walkFieldList(n.Fields, ast.Var)
+
+ case *ast.FuncType:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ r.walkFuncType(n)
+
+ case *ast.CompositeLit:
+ if n.Type != nil {
+ ast.Walk(r, n.Type)
+ }
+ for _, e := range n.Elts {
+ if kv, _ := e.(*ast.KeyValueExpr); kv != nil {
+ // See issue #45160: try to resolve composite lit keys, but don't
+ // collect them as unresolved if resolution failed. This replicates
+ // existing behavior when resolving during parsing.
+ if ident, _ := kv.Key.(*ast.Ident); ident != nil {
+ r.resolve(ident, false)
+ } else {
+ ast.Walk(r, kv.Key)
+ }
+ ast.Walk(r, kv.Value)
+ } else {
+ ast.Walk(r, e)
+ }
+ }
+
+ case *ast.InterfaceType:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ r.walkFieldList(n.Methods, ast.Fun)
+
+ // Statements
+ case *ast.LabeledStmt:
+ r.declare(n, nil, r.labelScope, ast.Lbl, n.Label)
+ ast.Walk(r, n.Stmt)
+
+ case *ast.AssignStmt:
+ r.walkExprs(n.Rhs)
+ if n.Tok == token.DEFINE {
+ r.shortVarDecl(n)
+ } else {
+ r.walkExprs(n.Lhs)
+ }
+
+ case *ast.BranchStmt:
+ // add to list of unresolved targets
+ if n.Tok != token.FALLTHROUGH && n.Label != nil {
+ depth := len(r.targetStack) - 1
+ r.targetStack[depth] = append(r.targetStack[depth], n.Label)
+ }
+
+ case *ast.BlockStmt:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ r.walkStmts(n.List)
+
+ case *ast.IfStmt:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ if n.Init != nil {
+ ast.Walk(r, n.Init)
+ }
+ ast.Walk(r, n.Cond)
+ ast.Walk(r, n.Body)
+ if n.Else != nil {
+ ast.Walk(r, n.Else)
+ }
+
+ case *ast.CaseClause:
+ r.walkExprs(n.List)
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ r.walkStmts(n.Body)
+
+ case *ast.SwitchStmt:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ if n.Init != nil {
+ ast.Walk(r, n.Init)
+ }
+ if n.Tag != nil {
+ // The scope below reproduces some unnecessary behavior of the parser,
+ // opening an extra scope in case this is a type switch. It's not needed
+ // for expression switches.
+ // TODO: remove this once we've matched the parser resolution exactly.
+ if n.Init != nil {
+ r.openScope(n.Tag.Pos())
+ defer r.closeScope()
+ }
+ ast.Walk(r, n.Tag)
+ }
+ if n.Body != nil {
+ r.walkStmts(n.Body.List)
+ }
+
+ case *ast.TypeSwitchStmt:
+ if n.Init != nil {
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ ast.Walk(r, n.Init)
+ }
+ r.openScope(n.Assign.Pos())
+ defer r.closeScope()
+ ast.Walk(r, n.Assign)
+ // s.Body consists only of case clauses, so does not get its own
+ // scope.
+ if n.Body != nil {
+ r.walkStmts(n.Body.List)
+ }
+
+ case *ast.CommClause:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ if n.Comm != nil {
+ ast.Walk(r, n.Comm)
+ }
+ r.walkStmts(n.Body)
+
+ case *ast.SelectStmt:
+ // as for switch statements, select statement bodies don't get their own
+ // scope.
+ if n.Body != nil {
+ r.walkStmts(n.Body.List)
+ }
+
+ case *ast.ForStmt:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ if n.Init != nil {
+ ast.Walk(r, n.Init)
+ }
+ if n.Cond != nil {
+ ast.Walk(r, n.Cond)
+ }
+ if n.Post != nil {
+ ast.Walk(r, n.Post)
+ }
+ ast.Walk(r, n.Body)
+
+ case *ast.RangeStmt:
+ r.openScope(n.Pos())
+ defer r.closeScope()
+ ast.Walk(r, n.X)
+ var lhs []ast.Expr
+ if n.Key != nil {
+ lhs = append(lhs, n.Key)
+ }
+ if n.Value != nil {
+ lhs = append(lhs, n.Value)
+ }
+ if len(lhs) > 0 {
+ if n.Tok == token.DEFINE {
+ // Note: we can't exactly match the behavior of object resolution
+ // during the parsing pass here, as it uses the position of the RANGE
+ // token for the RHS OpPos. That information is not contained within
+ // the AST.
+ as := &ast.AssignStmt{
+ Lhs: lhs,
+ Tok: token.DEFINE,
+ TokPos: n.TokPos,
+ Rhs: []ast.Expr{&ast.UnaryExpr{Op: token.RANGE, X: n.X}},
+ }
+ // TODO(rFindley): this walkLHS reproduced the parser resolution, but
+ // is it necessary? By comparison, for a normal AssignStmt we don't
+ // walk the LHS in case there is an invalid identifier list.
+ r.walkLHS(lhs)
+ r.shortVarDecl(as)
+ } else {
+ r.walkExprs(lhs)
+ }
+ }
+ ast.Walk(r, n.Body)
+
+ // Declarations
+ case *ast.GenDecl:
+ switch n.Tok {
+ case token.CONST, token.VAR:
+ for i, spec := range n.Specs {
+ spec := spec.(*ast.ValueSpec)
+ kind := ast.Con
+ if n.Tok == token.VAR {
+ kind = ast.Var
+ }
+ r.walkExprs(spec.Values)
+ if spec.Type != nil {
+ ast.Walk(r, spec.Type)
+ }
+ r.declare(spec, i, r.topScope, kind, spec.Names...)
+ }
+ case token.TYPE:
+ for _, spec := range n.Specs {
+ spec := spec.(*ast.TypeSpec)
+ // Go spec: The scope of a type identifier declared inside a function begins
+ // at the identifier in the TypeSpec and ends at the end of the innermost
+ // containing block.
+ r.declare(spec, nil, r.topScope, ast.Typ, spec.Name)
+ if spec.TypeParams != nil {
+ r.openScope(spec.Pos())
+ defer r.closeScope()
+ r.walkTParams(spec.TypeParams)
+ }
+ ast.Walk(r, spec.Type)
+ }
+ }
+
+ case *ast.FuncDecl:
+ // Open the function scope.
+ r.openScope(n.Pos())
+ defer r.closeScope()
+
+ r.walkRecv(n.Recv)
+
+ // Type parameters are walked normally: they can reference each other, and
+ // can be referenced by normal parameters.
+ if n.Type.TypeParams != nil {
+ r.walkTParams(n.Type.TypeParams)
+ // TODO(rFindley): need to address receiver type parameters.
+ }
+
+ // Resolve and declare parameters in a specific order to get duplicate
+ // declaration errors in the correct location.
+ r.resolveList(n.Type.Params)
+ r.resolveList(n.Type.Results)
+ r.declareList(n.Recv, ast.Var)
+ r.declareList(n.Type.Params, ast.Var)
+ r.declareList(n.Type.Results, ast.Var)
+
+ r.walkBody(n.Body)
+ if n.Recv == nil && n.Name.Name != "init" {
+ r.declare(n, nil, r.pkgScope, ast.Fun, n.Name)
+ }
+
+ default:
+ return r
+ }
+
+ return nil
+}
+
+func (r *resolver) walkFuncType(typ *ast.FuncType) {
+ // typ.TypeParams must be walked separately for FuncDecls.
+ r.resolveList(typ.Params)
+ r.resolveList(typ.Results)
+ r.declareList(typ.Params, ast.Var)
+ r.declareList(typ.Results, ast.Var)
+}
+
+func (r *resolver) resolveList(list *ast.FieldList) {
+ if list == nil {
+ return
+ }
+ for _, f := range list.List {
+ if f.Type != nil {
+ ast.Walk(r, f.Type)
+ }
+ }
+}
+
+func (r *resolver) declareList(list *ast.FieldList, kind ast.ObjKind) {
+ if list == nil {
+ return
+ }
+ for _, f := range list.List {
+ r.declare(f, nil, r.topScope, kind, f.Names...)
+ }
+}
+
+func (r *resolver) walkRecv(recv *ast.FieldList) {
+ // If our receiver has receiver type parameters, we must declare them before
+ // trying to resolve the rest of the receiver, and avoid re-resolving the
+ // type parameter identifiers.
+ if recv == nil || len(recv.List) == 0 {
+ return // nothing to do
+ }
+ typ := recv.List[0].Type
+ if ptr, ok := typ.(*ast.StarExpr); ok {
+ typ = ptr.X
+ }
+
+ var declareExprs []ast.Expr // exprs to declare
+ var resolveExprs []ast.Expr // exprs to resolve
+ switch typ := typ.(type) {
+ case *ast.IndexExpr:
+ declareExprs = []ast.Expr{typ.Index}
+ resolveExprs = append(resolveExprs, typ.X)
+ case *ast.IndexListExpr:
+ declareExprs = typ.Indices
+ resolveExprs = append(resolveExprs, typ.X)
+ default:
+ resolveExprs = append(resolveExprs, typ)
+ }
+ for _, expr := range declareExprs {
+ if id, _ := expr.(*ast.Ident); id != nil {
+ r.declare(expr, nil, r.topScope, ast.Typ, id)
+ } else {
+ // The receiver type parameter expression is invalid, but try to resolve
+ // it anyway for consistency.
+ resolveExprs = append(resolveExprs, expr)
+ }
+ }
+ for _, expr := range resolveExprs {
+ if expr != nil {
+ ast.Walk(r, expr)
+ }
+ }
+ // The receiver is invalid, but try to resolve it anyway for consistency.
+ for _, f := range recv.List[1:] {
+ if f.Type != nil {
+ ast.Walk(r, f.Type)
+ }
+ }
+}
+
+func (r *resolver) walkFieldList(list *ast.FieldList, kind ast.ObjKind) {
+ if list == nil {
+ return
+ }
+ r.resolveList(list)
+ r.declareList(list, kind)
+}
+
+// walkTParams is like walkFieldList, but declares type parameters eagerly so
+// that they may be resolved in the constraint expressions held in the field
+// Type.
+func (r *resolver) walkTParams(list *ast.FieldList) {
+ r.declareList(list, ast.Typ)
+ r.resolveList(list)
+}
+
+func (r *resolver) walkBody(body *ast.BlockStmt) {
+ if body == nil {
+ return
+ }
+ r.openLabelScope()
+ defer r.closeLabelScope()
+ r.walkStmts(body.List)
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-29 17:25:33 +0000