| // Copyright 2012 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. |
| |
| // This file implements typechecking of statements. |
| |
| package types |
| |
| import ( |
| "go/ast" |
| "go/constant" |
| "go/token" |
| "internal/buildcfg" |
| . "internal/types/errors" |
| "sort" |
| ) |
| |
| func (check *Checker) funcBody(decl *declInfo, name string, sig *Signature, body *ast.BlockStmt, iota constant.Value) { |
| if check.conf.IgnoreFuncBodies { |
| panic("function body not ignored") |
| } |
| |
| if check.conf._Trace { |
| check.trace(body.Pos(), "-- %s: %s", name, sig) |
| } |
| |
| // save/restore current environment and set up function environment |
| // (and use 0 indentation at function start) |
| defer func(env environment, indent int) { |
| check.environment = env |
| check.indent = indent |
| }(check.environment, check.indent) |
| check.environment = environment{ |
| decl: decl, |
| scope: sig.scope, |
| iota: iota, |
| sig: sig, |
| } |
| check.indent = 0 |
| |
| check.stmtList(0, body.List) |
| |
| if check.hasLabel { |
| check.labels(body) |
| } |
| |
| if sig.results.Len() > 0 && !check.isTerminating(body, "") { |
| check.error(atPos(body.Rbrace), MissingReturn, "missing return") |
| } |
| |
| // spec: "Implementation restriction: A compiler may make it illegal to |
| // declare a variable inside a function body if the variable is never used." |
| check.usage(sig.scope) |
| } |
| |
| func (check *Checker) usage(scope *Scope) { |
| var unused []*Var |
| for name, elem := range scope.elems { |
| elem = resolve(name, elem) |
| if v, _ := elem.(*Var); v != nil && !v.used { |
| unused = append(unused, v) |
| } |
| } |
| sort.Slice(unused, func(i, j int) bool { |
| return cmpPos(unused[i].pos, unused[j].pos) < 0 |
| }) |
| for _, v := range unused { |
| check.softErrorf(v, UnusedVar, "%s declared and not used", quote(v.name)) |
| } |
| |
| for _, scope := range scope.children { |
| // Don't go inside function literal scopes a second time; |
| // they are handled explicitly by funcBody. |
| if !scope.isFunc { |
| check.usage(scope) |
| } |
| } |
| } |
| |
| // stmtContext is a bitset describing which |
| // control-flow statements are permissible, |
| // and provides additional context information |
| // for better error messages. |
| type stmtContext uint |
| |
| const ( |
| // permissible control-flow statements |
| breakOk stmtContext = 1 << iota |
| continueOk |
| fallthroughOk |
| |
| // additional context information |
| finalSwitchCase |
| inTypeSwitch |
| ) |
| |
| func (check *Checker) simpleStmt(s ast.Stmt) { |
| if s != nil { |
| check.stmt(0, s) |
| } |
| } |
| |
| func trimTrailingEmptyStmts(list []ast.Stmt) []ast.Stmt { |
| for i := len(list); i > 0; i-- { |
| if _, ok := list[i-1].(*ast.EmptyStmt); !ok { |
| return list[:i] |
| } |
| } |
| return nil |
| } |
| |
| func (check *Checker) stmtList(ctxt stmtContext, list []ast.Stmt) { |
| ok := ctxt&fallthroughOk != 0 |
| inner := ctxt &^ fallthroughOk |
| list = trimTrailingEmptyStmts(list) // trailing empty statements are "invisible" to fallthrough analysis |
| for i, s := range list { |
| inner := inner |
| if ok && i+1 == len(list) { |
| inner |= fallthroughOk |
| } |
| check.stmt(inner, s) |
| } |
| } |
| |
| func (check *Checker) multipleDefaults(list []ast.Stmt) { |
| var first ast.Stmt |
| for _, s := range list { |
| var d ast.Stmt |
| switch c := s.(type) { |
| case *ast.CaseClause: |
| if len(c.List) == 0 { |
| d = s |
| } |
| case *ast.CommClause: |
| if c.Comm == nil { |
| d = s |
| } |
| default: |
| check.error(s, InvalidSyntaxTree, "case/communication clause expected") |
| } |
| if d != nil { |
| if first != nil { |
| check.errorf(d, DuplicateDefault, "multiple defaults (first at %s)", check.fset.Position(first.Pos())) |
| } else { |
| first = d |
| } |
| } |
| } |
| } |
| |
| func (check *Checker) openScope(node ast.Node, comment string) { |
| scope := NewScope(check.scope, node.Pos(), node.End(), comment) |
| check.recordScope(node, scope) |
| check.scope = scope |
| } |
| |
| func (check *Checker) closeScope() { |
| check.scope = check.scope.Parent() |
| } |
| |
| func assignOp(op token.Token) token.Token { |
| // token_test.go verifies the token ordering this function relies on |
| if token.ADD_ASSIGN <= op && op <= token.AND_NOT_ASSIGN { |
| return op + (token.ADD - token.ADD_ASSIGN) |
| } |
| return token.ILLEGAL |
| } |
| |
| func (check *Checker) suspendedCall(keyword string, call *ast.CallExpr) { |
| var x operand |
| var msg string |
| var code Code |
| switch check.rawExpr(nil, &x, call, nil, false) { |
| case conversion: |
| msg = "requires function call, not conversion" |
| code = InvalidDefer |
| if keyword == "go" { |
| code = InvalidGo |
| } |
| case expression: |
| msg = "discards result of" |
| code = UnusedResults |
| case statement: |
| return |
| default: |
| panic("unreachable") |
| } |
| check.errorf(&x, code, "%s %s %s", keyword, msg, &x) |
| } |
| |
| // goVal returns the Go value for val, or nil. |
| func goVal(val constant.Value) any { |
| // val should exist, but be conservative and check |
| if val == nil { |
| return nil |
| } |
| // Match implementation restriction of other compilers. |
| // gc only checks duplicates for integer, floating-point |
| // and string values, so only create Go values for these |
| // types. |
| switch val.Kind() { |
| case constant.Int: |
| if x, ok := constant.Int64Val(val); ok { |
| return x |
| } |
| if x, ok := constant.Uint64Val(val); ok { |
| return x |
| } |
| case constant.Float: |
| if x, ok := constant.Float64Val(val); ok { |
| return x |
| } |
| case constant.String: |
| return constant.StringVal(val) |
| } |
| return nil |
| } |
| |
| // A valueMap maps a case value (of a basic Go type) to a list of positions |
| // where the same case value appeared, together with the corresponding case |
| // types. |
| // Since two case values may have the same "underlying" value but different |
| // types we need to also check the value's types (e.g., byte(1) vs myByte(1)) |
| // when the switch expression is of interface type. |
| type ( |
| valueMap map[any][]valueType // underlying Go value -> valueType |
| valueType struct { |
| pos token.Pos |
| typ Type |
| } |
| ) |
| |
| func (check *Checker) caseValues(x *operand, values []ast.Expr, seen valueMap) { |
| L: |
| for _, e := range values { |
| var v operand |
| check.expr(nil, &v, e) |
| if x.mode == invalid || v.mode == invalid { |
| continue L |
| } |
| check.convertUntyped(&v, x.typ) |
| if v.mode == invalid { |
| continue L |
| } |
| // Order matters: By comparing v against x, error positions are at the case values. |
| res := v // keep original v unchanged |
| check.comparison(&res, x, token.EQL, true) |
| if res.mode == invalid { |
| continue L |
| } |
| if v.mode != constant_ { |
| continue L // we're done |
| } |
| // look for duplicate values |
| if val := goVal(v.val); val != nil { |
| // look for duplicate types for a given value |
| // (quadratic algorithm, but these lists tend to be very short) |
| for _, vt := range seen[val] { |
| if Identical(v.typ, vt.typ) { |
| err := check.newError(DuplicateCase) |
| err.addf(&v, "duplicate case %s in expression switch", &v) |
| err.addf(atPos(vt.pos), "previous case") |
| err.report() |
| continue L |
| } |
| } |
| seen[val] = append(seen[val], valueType{v.Pos(), v.typ}) |
| } |
| } |
| } |
| |
| // isNil reports whether the expression e denotes the predeclared value nil. |
| func (check *Checker) isNil(e ast.Expr) bool { |
| // The only way to express the nil value is by literally writing nil (possibly in parentheses). |
| if name, _ := ast.Unparen(e).(*ast.Ident); name != nil { |
| _, ok := check.lookup(name.Name).(*Nil) |
| return ok |
| } |
| return false |
| } |
| |
| // If the type switch expression is invalid, x is nil. |
| func (check *Checker) caseTypes(x *operand, types []ast.Expr, seen map[Type]ast.Expr) (T Type) { |
| var dummy operand |
| L: |
| for _, e := range types { |
| // The spec allows the value nil instead of a type. |
| if check.isNil(e) { |
| T = nil |
| check.expr(nil, &dummy, e) // run e through expr so we get the usual Info recordings |
| } else { |
| T = check.varType(e) |
| if !isValid(T) { |
| continue L |
| } |
| } |
| // look for duplicate types |
| // (quadratic algorithm, but type switches tend to be reasonably small) |
| for t, other := range seen { |
| if T == nil && t == nil || T != nil && t != nil && Identical(T, t) { |
| // talk about "case" rather than "type" because of nil case |
| Ts := "nil" |
| if T != nil { |
| Ts = TypeString(T, check.qualifier) |
| } |
| err := check.newError(DuplicateCase) |
| err.addf(e, "duplicate case %s in type switch", Ts) |
| err.addf(other, "previous case") |
| err.report() |
| continue L |
| } |
| } |
| seen[T] = e |
| if x != nil && T != nil { |
| check.typeAssertion(e, x, T, true) |
| } |
| } |
| return |
| } |
| |
| // TODO(gri) Once we are certain that typeHash is correct in all situations, use this version of caseTypes instead. |
| // (Currently it may be possible that different types have identical names and import paths due to ImporterFrom.) |
| // |
| // func (check *Checker) caseTypes(x *operand, xtyp *Interface, types []ast.Expr, seen map[string]ast.Expr) (T Type) { |
| // var dummy operand |
| // L: |
| // for _, e := range types { |
| // // The spec allows the value nil instead of a type. |
| // var hash string |
| // if check.isNil(e) { |
| // check.expr(nil, &dummy, e) // run e through expr so we get the usual Info recordings |
| // T = nil |
| // hash = "<nil>" // avoid collision with a type named nil |
| // } else { |
| // T = check.varType(e) |
| // if !isValid(T) { |
| // continue L |
| // } |
| // hash = typeHash(T, nil) |
| // } |
| // // look for duplicate types |
| // if other := seen[hash]; other != nil { |
| // // talk about "case" rather than "type" because of nil case |
| // Ts := "nil" |
| // if T != nil { |
| // Ts = TypeString(T, check.qualifier) |
| // } |
| // err := check.newError(_DuplicateCase) |
| // err.addf(e, "duplicate case %s in type switch", Ts) |
| // err.addf(other, "previous case") |
| // err.report() |
| // continue L |
| // } |
| // seen[hash] = e |
| // if T != nil { |
| // check.typeAssertion(e.Pos(), x, xtyp, T) |
| // } |
| // } |
| // return |
| // } |
| |
| // stmt typechecks statement s. |
| func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) { |
| // statements must end with the same top scope as they started with |
| if debug { |
| defer func(scope *Scope) { |
| // don't check if code is panicking |
| if p := recover(); p != nil { |
| panic(p) |
| } |
| assert(scope == check.scope) |
| }(check.scope) |
| } |
| |
| // process collected function literals before scope changes |
| defer check.processDelayed(len(check.delayed)) |
| |
| // reset context for statements of inner blocks |
| inner := ctxt &^ (fallthroughOk | finalSwitchCase | inTypeSwitch) |
| |
| switch s := s.(type) { |
| case *ast.BadStmt, *ast.EmptyStmt: |
| // ignore |
| |
| case *ast.DeclStmt: |
| check.declStmt(s.Decl) |
| |
| case *ast.LabeledStmt: |
| check.hasLabel = true |
| check.stmt(ctxt, s.Stmt) |
| |
| case *ast.ExprStmt: |
| // spec: "With the exception of specific built-in functions, |
| // function and method calls and receive operations can appear |
| // in statement context. Such statements may be parenthesized." |
| var x operand |
| kind := check.rawExpr(nil, &x, s.X, nil, false) |
| var msg string |
| var code Code |
| switch x.mode { |
| default: |
| if kind == statement { |
| return |
| } |
| msg = "is not used" |
| code = UnusedExpr |
| case builtin: |
| msg = "must be called" |
| code = UncalledBuiltin |
| case typexpr: |
| msg = "is not an expression" |
| code = NotAnExpr |
| } |
| check.errorf(&x, code, "%s %s", &x, msg) |
| |
| case *ast.SendStmt: |
| var ch, val operand |
| check.expr(nil, &ch, s.Chan) |
| check.expr(nil, &val, s.Value) |
| if ch.mode == invalid || val.mode == invalid { |
| return |
| } |
| u := coreType(ch.typ) |
| if u == nil { |
| check.errorf(inNode(s, s.Arrow), InvalidSend, invalidOp+"cannot send to %s: no core type", &ch) |
| return |
| } |
| uch, _ := u.(*Chan) |
| if uch == nil { |
| check.errorf(inNode(s, s.Arrow), InvalidSend, invalidOp+"cannot send to non-channel %s", &ch) |
| return |
| } |
| if uch.dir == RecvOnly { |
| check.errorf(inNode(s, s.Arrow), InvalidSend, invalidOp+"cannot send to receive-only channel %s", &ch) |
| return |
| } |
| check.assignment(&val, uch.elem, "send") |
| |
| case *ast.IncDecStmt: |
| var op token.Token |
| switch s.Tok { |
| case token.INC: |
| op = token.ADD |
| case token.DEC: |
| op = token.SUB |
| default: |
| check.errorf(inNode(s, s.TokPos), InvalidSyntaxTree, "unknown inc/dec operation %s", s.Tok) |
| return |
| } |
| |
| var x operand |
| check.expr(nil, &x, s.X) |
| if x.mode == invalid { |
| return |
| } |
| if !allNumeric(x.typ) { |
| check.errorf(s.X, NonNumericIncDec, invalidOp+"%s%s (non-numeric type %s)", s.X, s.Tok, x.typ) |
| return |
| } |
| |
| Y := &ast.BasicLit{ValuePos: s.X.Pos(), Kind: token.INT, Value: "1"} // use x's position |
| check.binary(&x, nil, s.X, Y, op, s.TokPos) |
| if x.mode == invalid { |
| return |
| } |
| check.assignVar(s.X, nil, &x, "assignment") |
| |
| case *ast.AssignStmt: |
| switch s.Tok { |
| case token.ASSIGN, token.DEFINE: |
| if len(s.Lhs) == 0 { |
| check.error(s, InvalidSyntaxTree, "missing lhs in assignment") |
| return |
| } |
| if s.Tok == token.DEFINE { |
| check.shortVarDecl(inNode(s, s.TokPos), s.Lhs, s.Rhs) |
| } else { |
| // regular assignment |
| check.assignVars(s.Lhs, s.Rhs) |
| } |
| |
| default: |
| // assignment operations |
| if len(s.Lhs) != 1 || len(s.Rhs) != 1 { |
| check.errorf(inNode(s, s.TokPos), MultiValAssignOp, "assignment operation %s requires single-valued expressions", s.Tok) |
| return |
| } |
| op := assignOp(s.Tok) |
| if op == token.ILLEGAL { |
| check.errorf(atPos(s.TokPos), InvalidSyntaxTree, "unknown assignment operation %s", s.Tok) |
| return |
| } |
| var x operand |
| check.binary(&x, nil, s.Lhs[0], s.Rhs[0], op, s.TokPos) |
| if x.mode == invalid { |
| return |
| } |
| check.assignVar(s.Lhs[0], nil, &x, "assignment") |
| } |
| |
| case *ast.GoStmt: |
| check.suspendedCall("go", s.Call) |
| |
| case *ast.DeferStmt: |
| check.suspendedCall("defer", s.Call) |
| |
| case *ast.ReturnStmt: |
| res := check.sig.results |
| // Return with implicit results allowed for function with named results. |
| // (If one is named, all are named.) |
| if len(s.Results) == 0 && res.Len() > 0 && res.vars[0].name != "" { |
| // spec: "Implementation restriction: A compiler may disallow an empty expression |
| // list in a "return" statement if a different entity (constant, type, or variable) |
| // with the same name as a result parameter is in scope at the place of the return." |
| for _, obj := range res.vars { |
| if alt := check.lookup(obj.name); alt != nil && alt != obj { |
| err := check.newError(OutOfScopeResult) |
| err.addf(s, "result parameter %s not in scope at return", quote(obj.name)) |
| err.addf(alt, "inner declaration of %s", obj) |
| err.report() |
| // ok to continue |
| } |
| } |
| } else { |
| var lhs []*Var |
| if res.Len() > 0 { |
| lhs = res.vars |
| } |
| check.initVars(lhs, s.Results, s) |
| } |
| |
| case *ast.BranchStmt: |
| if s.Label != nil { |
| check.hasLabel = true |
| return // checked in 2nd pass (check.labels) |
| } |
| switch s.Tok { |
| case token.BREAK: |
| if ctxt&breakOk == 0 { |
| check.error(s, MisplacedBreak, "break not in for, switch, or select statement") |
| } |
| case token.CONTINUE: |
| if ctxt&continueOk == 0 { |
| check.error(s, MisplacedContinue, "continue not in for statement") |
| } |
| case token.FALLTHROUGH: |
| if ctxt&fallthroughOk == 0 { |
| var msg string |
| switch { |
| case ctxt&finalSwitchCase != 0: |
| msg = "cannot fallthrough final case in switch" |
| case ctxt&inTypeSwitch != 0: |
| msg = "cannot fallthrough in type switch" |
| default: |
| msg = "fallthrough statement out of place" |
| } |
| check.error(s, MisplacedFallthrough, msg) |
| } |
| default: |
| check.errorf(s, InvalidSyntaxTree, "branch statement: %s", s.Tok) |
| } |
| |
| case *ast.BlockStmt: |
| check.openScope(s, "block") |
| defer check.closeScope() |
| |
| check.stmtList(inner, s.List) |
| |
| case *ast.IfStmt: |
| check.openScope(s, "if") |
| defer check.closeScope() |
| |
| check.simpleStmt(s.Init) |
| var x operand |
| check.expr(nil, &x, s.Cond) |
| if x.mode != invalid && !allBoolean(x.typ) { |
| check.error(s.Cond, InvalidCond, "non-boolean condition in if statement") |
| } |
| check.stmt(inner, s.Body) |
| // The parser produces a correct AST but if it was modified |
| // elsewhere the else branch may be invalid. Check again. |
| switch s.Else.(type) { |
| case nil, *ast.BadStmt: |
| // valid or error already reported |
| case *ast.IfStmt, *ast.BlockStmt: |
| check.stmt(inner, s.Else) |
| default: |
| check.error(s.Else, InvalidSyntaxTree, "invalid else branch in if statement") |
| } |
| |
| case *ast.SwitchStmt: |
| inner |= breakOk |
| check.openScope(s, "switch") |
| defer check.closeScope() |
| |
| check.simpleStmt(s.Init) |
| var x operand |
| if s.Tag != nil { |
| check.expr(nil, &x, s.Tag) |
| // By checking assignment of x to an invisible temporary |
| // (as a compiler would), we get all the relevant checks. |
| check.assignment(&x, nil, "switch expression") |
| if x.mode != invalid && !Comparable(x.typ) && !hasNil(x.typ) { |
| check.errorf(&x, InvalidExprSwitch, "cannot switch on %s (%s is not comparable)", &x, x.typ) |
| x.mode = invalid |
| } |
| } else { |
| // spec: "A missing switch expression is |
| // equivalent to the boolean value true." |
| x.mode = constant_ |
| x.typ = Typ[Bool] |
| x.val = constant.MakeBool(true) |
| x.expr = &ast.Ident{NamePos: s.Body.Lbrace, Name: "true"} |
| } |
| |
| check.multipleDefaults(s.Body.List) |
| |
| seen := make(valueMap) // map of seen case values to positions and types |
| for i, c := range s.Body.List { |
| clause, _ := c.(*ast.CaseClause) |
| if clause == nil { |
| check.error(c, InvalidSyntaxTree, "incorrect expression switch case") |
| continue |
| } |
| check.caseValues(&x, clause.List, seen) |
| check.openScope(clause, "case") |
| inner := inner |
| if i+1 < len(s.Body.List) { |
| inner |= fallthroughOk |
| } else { |
| inner |= finalSwitchCase |
| } |
| check.stmtList(inner, clause.Body) |
| check.closeScope() |
| } |
| |
| case *ast.TypeSwitchStmt: |
| inner |= breakOk | inTypeSwitch |
| check.openScope(s, "type switch") |
| defer check.closeScope() |
| |
| check.simpleStmt(s.Init) |
| |
| // A type switch guard must be of the form: |
| // |
| // TypeSwitchGuard = [ identifier ":=" ] PrimaryExpr "." "(" "type" ")" . |
| // |
| // The parser is checking syntactic correctness; |
| // remaining syntactic errors are considered AST errors here. |
| // TODO(gri) better factoring of error handling (invalid ASTs) |
| // |
| var lhs *ast.Ident // lhs identifier or nil |
| var rhs ast.Expr |
| switch guard := s.Assign.(type) { |
| case *ast.ExprStmt: |
| rhs = guard.X |
| case *ast.AssignStmt: |
| if len(guard.Lhs) != 1 || guard.Tok != token.DEFINE || len(guard.Rhs) != 1 { |
| check.error(s, InvalidSyntaxTree, "incorrect form of type switch guard") |
| return |
| } |
| |
| lhs, _ = guard.Lhs[0].(*ast.Ident) |
| if lhs == nil { |
| check.error(s, InvalidSyntaxTree, "incorrect form of type switch guard") |
| return |
| } |
| |
| if lhs.Name == "_" { |
| // _ := x.(type) is an invalid short variable declaration |
| check.softErrorf(lhs, NoNewVar, "no new variable on left side of :=") |
| lhs = nil // avoid declared and not used error below |
| } else { |
| check.recordDef(lhs, nil) // lhs variable is implicitly declared in each cause clause |
| } |
| |
| rhs = guard.Rhs[0] |
| |
| default: |
| check.error(s, InvalidSyntaxTree, "incorrect form of type switch guard") |
| return |
| } |
| |
| // rhs must be of the form: expr.(type) and expr must be an ordinary interface |
| expr, _ := rhs.(*ast.TypeAssertExpr) |
| if expr == nil || expr.Type != nil { |
| check.error(s, InvalidSyntaxTree, "incorrect form of type switch guard") |
| return |
| } |
| var x operand |
| check.expr(nil, &x, expr.X) |
| if x.mode == invalid { |
| return |
| } |
| // TODO(gri) we may want to permit type switches on type parameter values at some point |
| var sx *operand // switch expression against which cases are compared against; nil if invalid |
| if isTypeParam(x.typ) { |
| check.errorf(&x, InvalidTypeSwitch, "cannot use type switch on type parameter value %s", &x) |
| } else { |
| if _, ok := under(x.typ).(*Interface); ok { |
| sx = &x |
| } else { |
| check.errorf(&x, InvalidTypeSwitch, "%s is not an interface", &x) |
| } |
| } |
| |
| check.multipleDefaults(s.Body.List) |
| |
| var lhsVars []*Var // list of implicitly declared lhs variables |
| seen := make(map[Type]ast.Expr) // map of seen types to positions |
| for _, s := range s.Body.List { |
| clause, _ := s.(*ast.CaseClause) |
| if clause == nil { |
| check.error(s, InvalidSyntaxTree, "incorrect type switch case") |
| continue |
| } |
| // Check each type in this type switch case. |
| T := check.caseTypes(sx, clause.List, seen) |
| check.openScope(clause, "case") |
| // If lhs exists, declare a corresponding variable in the case-local scope. |
| if lhs != nil { |
| // spec: "The TypeSwitchGuard may include a short variable declaration. |
| // When that form is used, the variable is declared at the beginning of |
| // the implicit block in each clause. In clauses with a case listing |
| // exactly one type, the variable has that type; otherwise, the variable |
| // has the type of the expression in the TypeSwitchGuard." |
| if len(clause.List) != 1 || T == nil { |
| T = x.typ |
| } |
| obj := NewVar(lhs.Pos(), check.pkg, lhs.Name, T) |
| scopePos := clause.Pos() + token.Pos(len("default")) // for default clause (len(List) == 0) |
| if n := len(clause.List); n > 0 { |
| scopePos = clause.List[n-1].End() |
| } |
| check.declare(check.scope, nil, obj, scopePos) |
| check.recordImplicit(clause, obj) |
| // For the "declared and not used" error, all lhs variables act as |
| // one; i.e., if any one of them is 'used', all of them are 'used'. |
| // Collect them for later analysis. |
| lhsVars = append(lhsVars, obj) |
| } |
| check.stmtList(inner, clause.Body) |
| check.closeScope() |
| } |
| |
| // If lhs exists, we must have at least one lhs variable that was used. |
| if lhs != nil { |
| var used bool |
| for _, v := range lhsVars { |
| if v.used { |
| used = true |
| } |
| v.used = true // avoid usage error when checking entire function |
| } |
| if !used { |
| check.softErrorf(lhs, UnusedVar, "%s declared and not used", lhs.Name) |
| } |
| } |
| |
| case *ast.SelectStmt: |
| inner |= breakOk |
| |
| check.multipleDefaults(s.Body.List) |
| |
| for _, s := range s.Body.List { |
| clause, _ := s.(*ast.CommClause) |
| if clause == nil { |
| continue // error reported before |
| } |
| |
| // clause.Comm must be a SendStmt, RecvStmt, or default case |
| valid := false |
| var rhs ast.Expr // rhs of RecvStmt, or nil |
| switch s := clause.Comm.(type) { |
| case nil, *ast.SendStmt: |
| valid = true |
| case *ast.AssignStmt: |
| if len(s.Rhs) == 1 { |
| rhs = s.Rhs[0] |
| } |
| case *ast.ExprStmt: |
| rhs = s.X |
| } |
| |
| // if present, rhs must be a receive operation |
| if rhs != nil { |
| if x, _ := ast.Unparen(rhs).(*ast.UnaryExpr); x != nil && x.Op == token.ARROW { |
| valid = true |
| } |
| } |
| |
| if !valid { |
| check.error(clause.Comm, InvalidSelectCase, "select case must be send or receive (possibly with assignment)") |
| continue |
| } |
| |
| check.openScope(s, "case") |
| if clause.Comm != nil { |
| check.stmt(inner, clause.Comm) |
| } |
| check.stmtList(inner, clause.Body) |
| check.closeScope() |
| } |
| |
| case *ast.ForStmt: |
| inner |= breakOk | continueOk |
| check.openScope(s, "for") |
| defer check.closeScope() |
| |
| check.simpleStmt(s.Init) |
| if s.Cond != nil { |
| var x operand |
| check.expr(nil, &x, s.Cond) |
| if x.mode != invalid && !allBoolean(x.typ) { |
| check.error(s.Cond, InvalidCond, "non-boolean condition in for statement") |
| } |
| } |
| check.simpleStmt(s.Post) |
| // spec: "The init statement may be a short variable |
| // declaration, but the post statement must not." |
| if s, _ := s.Post.(*ast.AssignStmt); s != nil && s.Tok == token.DEFINE { |
| check.softErrorf(s, InvalidPostDecl, "cannot declare in post statement") |
| // Don't call useLHS here because we want to use the lhs in |
| // this erroneous statement so that we don't get errors about |
| // these lhs variables being declared and not used. |
| check.use(s.Lhs...) // avoid follow-up errors |
| } |
| check.stmt(inner, s.Body) |
| |
| case *ast.RangeStmt: |
| inner |= breakOk | continueOk |
| check.rangeStmt(inner, s) |
| |
| default: |
| check.error(s, InvalidSyntaxTree, "invalid statement") |
| } |
| } |
| |
| func (check *Checker) rangeStmt(inner stmtContext, s *ast.RangeStmt) { |
| // Convert go/ast form to local variables. |
| type Expr = ast.Expr |
| type identType = ast.Ident |
| identName := func(n *identType) string { return n.Name } |
| sKey, sValue := s.Key, s.Value |
| var sExtra ast.Expr = nil // (used only in types2 fork) |
| isDef := s.Tok == token.DEFINE |
| rangeVar := s.X |
| noNewVarPos := inNode(s, s.TokPos) |
| |
| // Everything from here on is shared between cmd/compile/internal/types2 and go/types. |
| |
| // check expression to iterate over |
| var x operand |
| check.expr(nil, &x, rangeVar) |
| |
| // determine key/value types |
| var key, val Type |
| if x.mode != invalid { |
| // Ranging over a type parameter is permitted if it has a core type. |
| k, v, cause, isFunc, ok := rangeKeyVal(x.typ, func(v goVersion) bool { |
| return check.allowVersion(x.expr, v) |
| }) |
| switch { |
| case !ok && cause != "": |
| check.softErrorf(&x, InvalidRangeExpr, "cannot range over %s: %s", &x, cause) |
| case !ok: |
| check.softErrorf(&x, InvalidRangeExpr, "cannot range over %s", &x) |
| case k == nil && sKey != nil: |
| check.softErrorf(sKey, InvalidIterVar, "range over %s permits no iteration variables", &x) |
| case v == nil && sValue != nil: |
| check.softErrorf(sValue, InvalidIterVar, "range over %s permits only one iteration variable", &x) |
| case sExtra != nil: |
| check.softErrorf(sExtra, InvalidIterVar, "range clause permits at most two iteration variables") |
| case isFunc && ((k == nil) != (sKey == nil) || (v == nil) != (sValue == nil)): |
| var count string |
| switch { |
| case k == nil: |
| count = "no iteration variables" |
| case v == nil: |
| count = "one iteration variable" |
| default: |
| count = "two iteration variables" |
| } |
| check.softErrorf(&x, InvalidIterVar, "range over %s must have %s", &x, count) |
| } |
| key, val = k, v |
| } |
| |
| // Open the for-statement block scope now, after the range clause. |
| // Iteration variables declared with := need to go in this scope (was go.dev/issue/51437). |
| check.openScope(s, "range") |
| defer check.closeScope() |
| |
| // check assignment to/declaration of iteration variables |
| // (irregular assignment, cannot easily map to existing assignment checks) |
| |
| // lhs expressions and initialization value (rhs) types |
| lhs := [2]Expr{sKey, sValue} // sKey, sValue may be nil |
| rhs := [2]Type{key, val} // key, val may be nil |
| |
| constIntRange := x.mode == constant_ && isInteger(x.typ) |
| |
| if isDef { |
| // short variable declaration |
| var vars []*Var |
| for i, lhs := range lhs { |
| if lhs == nil { |
| continue |
| } |
| |
| // determine lhs variable |
| var obj *Var |
| if ident, _ := lhs.(*identType); ident != nil { |
| // declare new variable |
| name := identName(ident) |
| obj = NewVar(ident.Pos(), check.pkg, name, nil) |
| check.recordDef(ident, obj) |
| // _ variables don't count as new variables |
| if name != "_" { |
| vars = append(vars, obj) |
| } |
| } else { |
| check.errorf(lhs, InvalidSyntaxTree, "cannot declare %s", lhs) |
| obj = NewVar(lhs.Pos(), check.pkg, "_", nil) // dummy variable |
| } |
| assert(obj.typ == nil) |
| |
| // initialize lhs iteration variable, if any |
| typ := rhs[i] |
| if typ == nil { |
| obj.typ = Typ[Invalid] |
| obj.used = true // don't complain about unused variable |
| continue |
| } |
| |
| // initialize lhs variable |
| if constIntRange { |
| check.initVar(obj, &x, "range clause") |
| } else { |
| x.mode = value |
| x.expr = lhs // we don't have a better rhs expression to use here |
| x.typ = typ |
| check.initVar(obj, &x, "assignment") // error is on variable, use "assignment" not "range clause" |
| } |
| assert(obj.typ != nil) |
| } |
| |
| // declare variables |
| if len(vars) > 0 { |
| scopePos := s.Body.Pos() |
| for _, obj := range vars { |
| check.declare(check.scope, nil /* recordDef already called */, obj, scopePos) |
| } |
| } else { |
| check.error(noNewVarPos, NoNewVar, "no new variables on left side of :=") |
| } |
| } else if sKey != nil /* lhs[0] != nil */ { |
| // ordinary assignment |
| for i, lhs := range lhs { |
| if lhs == nil { |
| continue |
| } |
| |
| // assign to lhs iteration variable, if any |
| typ := rhs[i] |
| if typ == nil { |
| continue |
| } |
| |
| if constIntRange { |
| check.assignVar(lhs, nil, &x, "range clause") |
| } else { |
| x.mode = value |
| x.expr = lhs // we don't have a better rhs expression to use here |
| x.typ = typ |
| check.assignVar(lhs, nil, &x, "assignment") // error is on variable, use "assignment" not "range clause" |
| } |
| } |
| } else if constIntRange { |
| // If we don't have any iteration variables, we still need to |
| // check that a (possibly untyped) integer range expression x |
| // is valid. |
| // We do this by checking the assignment _ = x. This ensures |
| // that an untyped x can be converted to a value of type int. |
| check.assignment(&x, nil, "range clause") |
| } |
| |
| check.stmt(inner, s.Body) |
| } |
| |
| // rangeKeyVal returns the key and value type produced by a range clause |
| // over an expression of type typ. |
| // If allowVersion != nil, it is used to check the required language version. |
| // If the range clause is not permitted, rangeKeyVal returns ok = false. |
| // When ok = false, rangeKeyVal may also return a reason in cause. |
| func rangeKeyVal(typ Type, allowVersion func(goVersion) bool) (key, val Type, cause string, isFunc, ok bool) { |
| bad := func(cause string) (Type, Type, string, bool, bool) { |
| return Typ[Invalid], Typ[Invalid], cause, false, false |
| } |
| toSig := func(t Type) *Signature { |
| sig, _ := coreType(t).(*Signature) |
| return sig |
| } |
| |
| orig := typ |
| switch typ := arrayPtrDeref(coreType(typ)).(type) { |
| case nil: |
| return bad("no core type") |
| case *Basic: |
| if isString(typ) { |
| return Typ[Int], universeRune, "", false, true // use 'rune' name |
| } |
| if isInteger(typ) { |
| if allowVersion != nil && !allowVersion(go1_22) { |
| return bad("requires go1.22 or later") |
| } |
| return orig, nil, "", false, true |
| } |
| case *Array: |
| return Typ[Int], typ.elem, "", false, true |
| case *Slice: |
| return Typ[Int], typ.elem, "", false, true |
| case *Map: |
| return typ.key, typ.elem, "", false, true |
| case *Chan: |
| if typ.dir == SendOnly { |
| return bad("receive from send-only channel") |
| } |
| return typ.elem, nil, "", false, true |
| case *Signature: |
| if !buildcfg.Experiment.RangeFunc && allowVersion != nil && !allowVersion(go1_23) { |
| return bad("requires go1.23 or later") |
| } |
| assert(typ.Recv() == nil) |
| switch { |
| case typ.Params().Len() != 1: |
| return bad("func must be func(yield func(...) bool): wrong argument count") |
| case toSig(typ.Params().At(0).Type()) == nil: |
| return bad("func must be func(yield func(...) bool): argument is not func") |
| case typ.Results().Len() != 0: |
| return bad("func must be func(yield func(...) bool): unexpected results") |
| } |
| cb := toSig(typ.Params().At(0).Type()) |
| assert(cb.Recv() == nil) |
| switch { |
| case cb.Params().Len() > 2: |
| return bad("func must be func(yield func(...) bool): yield func has too many parameters") |
| case cb.Results().Len() != 1 || !isBoolean(cb.Results().At(0).Type()): |
| return bad("func must be func(yield func(...) bool): yield func does not return bool") |
| } |
| if cb.Params().Len() >= 1 { |
| key = cb.Params().At(0).Type() |
| } |
| if cb.Params().Len() >= 2 { |
| val = cb.Params().At(1).Type() |
| } |
| return key, val, "", true, true |
| } |
| return |
| } |
