func (p *parser) parseCallOrConversion(fun ast.Expr) *ast.CallExpr {
if p.trace {
defer un(trace(p, "CallOrConversion"))
}
lparen := p.expect(token.LPAREN)
p.exprLev++
var list []ast.Expr
var ellipsis token.Pos
for p.tok != token.RPAREN && p.tok != token.EOF && !ellipsis.IsValid() {
list = append(list, p.parseExpr())
if p.tok == token.ELLIPSIS {
ellipsis = p.pos
p.next()
}
if p.tok != token.COMMA {
break
}
p.next()
}
p.exprLev--
rparen := p.expect(token.RPAREN)
return &ast.CallExpr{fun, lparen, list, ellipsis, rparen}
}
// If returnPos is valid, initVars is called to type-check the assignment of
// return expressions, and returnPos is the position of the return statement.
func (check *checker) initVars(lhs []*Var, rhs []ast.Expr, returnPos token.Pos) {
l := len(lhs)
get, r, commaOk := unpack(func(x *operand, i int) { check.expr(x, rhs[i]) }, len(rhs), l == 2 && !returnPos.IsValid())
if l != r {
// invalidate lhs
for _, obj := range lhs {
if obj.Type == nil {
obj.Type = Typ[Invalid]
}
}
if returnPos.IsValid() {
check.errorf(returnPos, "wrong number of return values (want %d, got %d)", l, r)
return
}
check.errorf(rhs[0].Pos(), "assignment count mismatch (%d vs %d)", l, r)
return
}
var x operand
if commaOk {
var a [2]Type
for i := range a {
get(&x, i)
a[i] = check.initVar(lhs[i], &x)
}
check.recordCommaOkTypes(rhs[0], a)
return
}
for i, lhs := range lhs {
get(&x, i)
check.initVar(lhs, &x)
}
}
func debugCall(fName string, pos token.Pos, args ...string) []byte {
vals := make(map[string]string)
if len(args) > 0 {
vals["args"] = strings.Join(args, ", ")
} else {
vals["args"] = ""
}
if timing {
vals["timing"] = "true"
}
vals["fname"] = fName
if pos.IsValid() {
vals["position"] = fset.Position(pos).String()
}
if showReturn {
vals["return"] = "true"
}
var b bytes.Buffer
err := funcTemplate.Execute(&b, vals)
if err != nil {
log.Fatal(err)
}
return b.Bytes()
}
func (check *checker) declareObj(scope, altScope *Scope, obj Object, dotImport token.Pos) {
alt := scope.Insert(obj)
if alt == nil && altScope != nil {
// see if there is a conflicting declaration in altScope
alt = altScope.Lookup(obj.Name())
}
if alt != nil {
prevDecl := ""
// for dot-imports, local declarations are declared first - swap messages
if dotImport.IsValid() {
if pos := alt.Pos(); pos.IsValid() {
check.errorf(pos, fmt.Sprintf("%s redeclared in this block by dot-import at %s",
obj.Name(), check.fset.Position(dotImport)))
return
}
// get by w/o other position
check.errorf(dotImport, fmt.Sprintf("dot-import redeclares %s", obj.Name()))
return
}
if pos := alt.Pos(); pos.IsValid() {
prevDecl = fmt.Sprintf("\n\tother declaration at %s", check.fset.Position(pos))
}
check.errorf(obj.Pos(), fmt.Sprintf("%s redeclared in this block%s", obj.Name(), prevDecl))
}
}
// distanceFrom returns the column difference between from and p.pos (the current
// estimated position) if both are on the same line; if they are on different lines
// (or unknown) the result is infinity.
func (p *printer) distanceFrom(from token.Pos) int {
if from.IsValid() && p.pos.IsValid() {
if f := p.posFor(from); f.Line == p.pos.Line {
return p.pos.Column - f.Column
}
}
return infinity
}
func error_(pos token.Pos, msg string, args ...interface{}) {
nerrors++
if pos.IsValid() {
fmt.Fprintf(os.Stderr, "%s: ", fset.Position(pos).String())
}
fmt.Fprintf(os.Stderr, msg, args...)
fmt.Fprintf(os.Stderr, "\n")
}
func warn(pos token.Pos, msg string, args ...interface{}) {
if pos.IsValid() {
msg = "%s: " + msg
arg1 := []interface{}{fset.Position(pos).String()}
args = append(arg1, args...)
}
fmt.Fprintf(os.Stderr, msg+"\n", args...)
}
// LookupParent follows the parent chain of scopes starting with s until
// it finds a scope where Lookup(name) returns a non-nil object, and then
// returns that scope and object. If a valid position pos is provided,
// only objects that were declared at or before pos are considered.
// If no such scope and object exists, the result is (nil, nil).
//
// Note that obj.Parent() may be different from the returned scope if the
// object was inserted into the scope and already had a parent at that
// time (see Insert, below). This can only happen for dot-imported objects
// whose scope is the scope of the package that exported them.
func (s *Scope) LookupParent(name string, pos token.Pos) (*Scope, Object) {
for ; s != nil; s = s.parent {
if obj := s.elems[name]; obj != nil && (!pos.IsValid() || obj.scopePos() <= pos) {
return s, obj
}
}
return nil, nil
}
// SetLocation sets the current debug location.
func (d *DIBuilder) SetLocation(b llvm.Builder, pos token.Pos) {
if !pos.IsValid() {
return
}
position := d.fset.Position(pos)
d.lb = llvm.Metadata{}
if position.Filename != d.fnFile && position.Filename != "" {
// This can happen rarely, e.g. in init functions.
diFile := d.builder.CreateFile(d.remapFilePath(position.Filename), "")
d.lb = d.builder.CreateLexicalBlockFile(d.scope(), diFile, 0)
}
b.SetCurrentDebugLocation(uint(position.Line), uint(position.Column), d.scope(), llvm.Metadata{})
}
// Eval returns the type and, if constant, the value for the
// expression expr, evaluated at position pos of package pkg,
// which must have been derived from type-checking an AST with
// complete position information relative to the provided file
// set.
//
// If the expression contains function literals, their bodies
// are ignored (i.e., the bodies are not type-checked).
//
// If pkg == nil, the Universe scope is used and the provided
// position pos is ignored. If pkg != nil, and pos is invalid,
// the package scope is used. Otherwise, pos must belong to the
// package.
//
// An error is returned if pos is not within the package or
// if the node cannot be evaluated.
//
// Note: Eval should not be used instead of running Check to compute
// types and values, but in addition to Check. Eval will re-evaluate
// its argument each time, and it also does not know about the context
// in which an expression is used (e.g., an assignment). Thus, top-
// level untyped constants will return an untyped type rather then the
// respective context-specific type.
//
func Eval(fset *token.FileSet, pkg *Package, pos token.Pos, expr string) (tv TypeAndValue, err error) {
// determine scope
var scope *Scope
if pkg == nil {
scope = Universe
pos = token.NoPos
} else if !pos.IsValid() {
scope = pkg.scope
} else {
// The package scope extent (position information) may be
// incorrect (files spread accross a wide range of fset
// positions) - ignore it and just consider its children
// (file scopes).
for _, fscope := range pkg.scope.children {
if scope = fscope.Innermost(pos); scope != nil {
break
}
}
if scope == nil || debug {
s := scope
for s != nil && s != pkg.scope {
s = s.parent
}
// s == nil || s == pkg.scope
if s == nil {
return TypeAndValue{}, fmt.Errorf("no position %s found in package %s", fset.Position(pos), pkg.name)
}
}
}
// parse expressions
// BUG(gri) In case of type-checking errors below, the type checker
// doesn't have the correct file set for expr. The correct
// solution requires a ParseExpr that uses the incoming
// file set fset.
node, err := parser.ParseExpr(expr)
if err != nil {
return TypeAndValue{}, err
}
// initialize checker
check := NewChecker(nil, fset, pkg, nil)
check.scope = scope
check.pos = pos
defer check.handleBailout(&err)
// evaluate node
var x operand
check.rawExpr(&x, node, nil)
return TypeAndValue{x.mode, x.typ, x.val}, err
}
// MakePosHash keeps track of references put into the code for later extraction in a runtime debug function.
// It returns the PosHash integer to be used for exception handling that was passed in.
func MakePosHash(pos token.Pos) PosHash {
if pos.IsValid() {
fname := rootProgram.Fset.Position(pos).Filename
for f := range PosHashFileList {
if PosHashFileList[f].FileName == fname {
LatestValidPosHash = PosHash(PosHashFileList[f].BasePosHash + rootProgram.Fset.Position(pos).Line)
return LatestValidPosHash
}
}
panic(fmt.Errorf("pogo.MakePosHash() Cant find file: %s", fname))
} else {
if LatestValidPosHash == NoPosHash {
return NoPosHash
}
return -LatestValidPosHash // -ve value => nearby reference
}
}
// argument checks passing of argument x to the i'th parameter of the given signature.
// If ellipsis is valid, the argument is followed by ... at that position in the call.
func (check *Checker) argument(sig *Signature, i int, x *operand, ellipsis token.Pos) {
n := sig.params.Len()
// determine parameter type
var typ Type
switch {
case i < n:
typ = sig.params.vars[i].typ
case sig.variadic:
typ = sig.params.vars[n-1].typ
if debug {
if _, ok := typ.(*Slice); !ok {
check.dump("%s: expected unnamed slice type, got %s", sig.params.vars[n-1].Pos(), typ)
}
}
default:
check.errorf(x.pos(), "too many arguments")
return
}
if ellipsis.IsValid() {
// argument is of the form x...
if i != n-1 {
check.errorf(ellipsis, "can only use ... with matching parameter")
return
}
switch t := x.typ.Underlying().(type) {
case *Slice:
// ok
case *Tuple:
check.errorf(ellipsis, "cannot use ... with %d-valued expression %s", t.Len(), x)
return
default:
check.errorf(x.pos(), "cannot use %s as parameter of type %s", x, typ)
return
}
} else if sig.variadic && i >= n-1 {
// use the variadic parameter slice's element type
typ = typ.(*Slice).elem
}
if !check.assignment(x, typ) && x.mode != invalid {
check.errorf(x.pos(), "cannot pass argument %s to parameter of type %s", x, typ)
}
}
// SetLocation sets the current debug location.
func (d *DIBuilder) SetLocation(b llvm.Builder, pos token.Pos) {
if !pos.IsValid() {
return
}
position := d.fset.Position(pos)
d.lb = llvm.Value{nil}
if position.Filename != d.fnFile && position.Filename != "" {
// This can happen rarely, e.g. in init functions.
diFile := d.builder.CreateFile(d.remapFilePath(position.Filename), "")
d.lb = d.builder.CreateLexicalBlockFile(d.scope(), diFile, 0)
}
b.SetCurrentDebugLocation(llvm.MDNode([]llvm.Value{
llvm.ConstInt(llvm.Int32Type(), uint64(position.Line), false),
llvm.ConstInt(llvm.Int32Type(), uint64(position.Column), false),
d.scope(),
llvm.Value{},
}))
}
// If returnPos is valid, initVars is called to type-check the assignment of
// return expressions, and returnPos is the position of the return statement.
func (check *Checker) initVars(lhs []*Var, rhs []ast.Expr, returnPos token.Pos) {
l := len(lhs)
get, r, commaOk := unpack(func(x *operand, i int) { check.multiExpr(x, rhs[i]) }, len(rhs), l == 2 && !returnPos.IsValid())
if get == nil || l != r {
// invalidate lhs and use rhs
for _, obj := range lhs {
if obj.typ == nil {
obj.typ = Typ[Invalid]
}
}
if get == nil {
return // error reported by unpack
}
check.useGetter(get, r)
if returnPos.IsValid() {
check.errorf(returnPos, "wrong number of return values (want %d, got %d)", l, r)
return
}
check.errorf(rhs[0].Pos(), "assignment count mismatch (%d vs %d)", l, r)
return
}
context := "assignment"
if returnPos.IsValid() {
context = "return statement"
}
var x operand
if commaOk {
var a [2]Type
for i := range a {
get(&x, i)
a[i] = check.initVar(lhs[i], &x, context)
}
check.recordCommaOkTypes(rhs[0], a)
return
}
for i, lhs := range lhs {
get(&x, i)
check.initVar(lhs, &x, context)
}
}
// argument checks passing of argument x to the i'th parameter of the given signature.
// If ellipsis is valid, the argument is followed by ... at that position in the call.
func (check *Checker) argument(fun ast.Expr, sig *Signature, i int, x *operand, ellipsis token.Pos) {
check.singleValue(x)
if x.mode == invalid {
return
}
n := sig.params.Len()
// determine parameter type
var typ Type
switch {
case i < n:
typ = sig.params.vars[i].typ
case sig.variadic:
typ = sig.params.vars[n-1].typ
if debug {
if _, ok := typ.(*Slice); !ok {
check.dump("%s: expected unnamed slice type, got %s", sig.params.vars[n-1].Pos(), typ)
}
}
default:
check.errorf(x.pos(), "too many arguments")
return
}
if ellipsis.IsValid() {
// argument is of the form x... and x is single-valued
if i != n-1 {
check.errorf(ellipsis, "can only use ... with matching parameter")
return
}
if _, ok := x.typ.Underlying().(*Slice); !ok {
check.errorf(x.pos(), "cannot use %s as parameter of type %s", x, typ)
return
}
} else if sig.variadic && i >= n-1 {
// use the variadic parameter slice's element type
typ = typ.(*Slice).elem
}
check.assignment(x, typ, check.sprintf("argument to %s", fun))
}
func newPosLink_urlFunc(srcPosLinkFunc func(s string, line, low, high int) string) func(info *PageInfo, n interface{}) string {
// n must be an ast.Node or a *doc.Note
return func(info *PageInfo, n interface{}) string {
var pos, end token.Pos
switch n := n.(type) {
case ast.Node:
pos = n.Pos()
end = n.End()
case *doc.Note:
pos = n.Pos
end = n.End
default:
panic(fmt.Sprintf("wrong type for posLink_url template formatter: %T", n))
}
var relpath string
var line int
var low, high int // selection offset range
if pos.IsValid() {
p := info.FSet.Position(pos)
relpath = p.Filename
line = p.Line
low = p.Offset
}
if end.IsValid() {
high = info.FSet.Position(end).Offset
}
return srcPosLinkFunc(relpath, line, low, high)
}
}
// n must be an ast.Node or a *doc.Note
func posLink_urlFunc(info *PageInfo, n interface{}) string {
var pos, end token.Pos
switch n := n.(type) {
case ast.Node:
pos = n.Pos()
end = n.End()
case *doc.Note:
pos = n.Pos
end = n.End
default:
panic(fmt.Sprintf("wrong type for posLink_url template formatter: %T", n))
}
var relpath string
var line int
var low, high int // selection offset range
if pos.IsValid() {
p := info.FSet.Position(pos)
relpath = p.Filename
line = p.Line
low = p.Offset
}
if end.IsValid() {
high = info.FSet.Position(end).Offset
}
var buf bytes.Buffer
template.HTMLEscape(&buf, []byte(relpath))
// selection ranges are of form "s=low:high"
if low < high {
fmt.Fprintf(&buf, "?s=%d:%d", low, high) // no need for URL escaping
// if we have a selection, position the page
// such that the selection is a bit below the top
line -= 10
if line < 1 {
line = 1
}
}
// line id's in html-printed source are of the
// form "L%d" where %d stands for the line number
if line > 0 {
fmt.Fprintf(&buf, "#L%d", line) // no need for URL escaping
}
return buf.String()
}
// If returnPos is valid, initVars is called to type-check the assignment of
// return expressions, and returnPos is the position of the return statement.
func (check *checker) initVars(lhs []*Var, rhs []ast.Expr, returnPos token.Pos) {
l := len(lhs)
r := len(rhs)
assert(l > 0)
// If the lhs and rhs have corresponding expressions,
// treat each matching pair as an individual pair.
if l == r {
var x operand
for i, e := range rhs {
check.expr(&x, e)
check.initVar(lhs[i], &x)
}
return
}
// Otherwise, the rhs must be a single expression (possibly
// a function call returning multiple values, or a comma-ok
// expression).
if r == 1 {
// l > 1
// Start with rhs so we have expression types
// for declarations with implicit types.
var x operand
rhs := rhs[0]
check.expr(&x, rhs)
if x.mode == invalid {
invalidateVars(lhs)
return
}
if t, ok := x.typ.(*Tuple); ok {
// function result
r = t.Len()
if l == r {
for i, lhs := range lhs {
x.mode = value
x.expr = rhs
x.typ = t.At(i).typ
check.initVar(lhs, &x)
}
return
}
}
if !returnPos.IsValid() && x.mode == valueok && l == 2 {
// comma-ok expression (not permitted with return statements)
x.mode = value
t1 := check.initVar(lhs[0], &x)
x.mode = value
x.expr = rhs
x.typ = Typ[UntypedBool]
t2 := check.initVar(lhs[1], &x)
if t1 != nil && t2 != nil {
check.recordCommaOkTypes(rhs, t1, t2)
}
return
}
}
invalidateVars(lhs)
// lhs variables may be function result parameters (return statement);
// use rhs position for properly located error messages
if returnPos.IsValid() {
check.errorf(returnPos, "wrong number of return values (want %d, got %d)", l, r)
return
}
check.errorf(rhs[0].Pos(), "assignment count mismatch (%d vs %d)", l, r)
}
// stmt typechecks statement s.
func (check *checker) stmt(ctxt stmtContext, s ast.Stmt) {
// statements cannot use iota in general
// (constant declarations set it explicitly)
assert(check.iota == nil)
// 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.topScope)
}(check.topScope)
}
inner := ctxt &^ fallthroughOk
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(&x, s.X, nil)
var msg string
switch x.mode {
default:
if kind == statement {
return
}
msg = "is not used"
case builtin:
msg = "must be called"
case typexpr:
msg = "is not an expression"
}
check.errorf(x.pos(), "%s %s", &x, msg)
case *ast.SendStmt:
var ch, x operand
check.expr(&ch, s.Chan)
check.expr(&x, s.Value)
if ch.mode == invalid || x.mode == invalid {
return
}
if tch, ok := ch.typ.Underlying().(*Chan); !ok || tch.dir&ast.SEND == 0 || !check.assignment(&x, tch.elt) {
if x.mode != invalid {
check.invalidOp(ch.pos(), "cannot send %s to channel %s", &x, &ch)
}
}
case *ast.IncDecStmt:
var op token.Token
switch s.Tok {
case token.INC:
op = token.ADD
case token.DEC:
op = token.SUB
default:
check.invalidAST(s.TokPos, "unknown inc/dec operation %s", s.Tok)
return
}
var x operand
Y := &ast.BasicLit{ValuePos: s.X.Pos(), Kind: token.INT, Value: "1"} // use x's position
check.binary(&x, s.X, Y, op, nil)
if x.mode == invalid {
return
}
check.assignVar(s.X, &x)
case *ast.AssignStmt:
switch s.Tok {
case token.ASSIGN, token.DEFINE:
if len(s.Lhs) == 0 {
check.invalidAST(s.Pos(), "missing lhs in assignment")
return
}
if s.Tok == token.DEFINE {
check.shortVarDecl(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(s.TokPos, "assignment operation %s requires single-valued expressions", s.Tok)
return
}
op := assignOp(s.Tok)
if op == token.ILLEGAL {
check.invalidAST(s.TokPos, "unknown assignment operation %s", s.Tok)
return
}
var x operand
check.binary(&x, s.Lhs[0], s.Rhs[0], op, nil)
if x.mode == invalid {
return
}
check.assignVar(s.Lhs[0], &x)
}
case *ast.GoStmt:
check.suspendedCall("go", s.Call)
case *ast.DeferStmt:
check.suspendedCall("defer", s.Call)
case *ast.ReturnStmt:
sig := check.funcSig
if n := sig.results.Len(); n > 0 {
// determine if the function has named results
named := false
lhs := make([]*Var, n)
for i, res := range sig.results.vars {
if res.name != "" {
// a blank (_) result parameter is a named result
named = true
}
lhs[i] = res
}
if len(s.Results) > 0 || !named {
check.initVars(lhs, s.Results, s.Return)
return
}
} else if len(s.Results) > 0 {
check.errorf(s.Pos(), "no result values expected")
}
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&inBreakable == 0 {
check.errorf(s.Pos(), "break not in for, switch, or select statement")
}
case token.CONTINUE:
if ctxt&inContinuable == 0 {
check.errorf(s.Pos(), "continue not in for statement")
}
case token.FALLTHROUGH:
if ctxt&fallthroughOk == 0 {
check.errorf(s.Pos(), "fallthrough statement out of place")
}
default:
check.invalidAST(s.Pos(), "branch statement: %s", s.Tok)
}
case *ast.BlockStmt:
check.openScope(s)
check.stmtList(inner, s.List)
check.closeScope()
case *ast.IfStmt:
check.openScope(s)
check.initStmt(s.Init)
var x operand
check.expr(&x, s.Cond)
if x.mode != invalid && !isBoolean(x.typ) {
check.errorf(s.Cond.Pos(), "non-boolean condition in if statement")
}
check.stmt(inner, s.Body)
if s.Else != nil {
check.stmt(inner, s.Else)
}
check.closeScope()
case *ast.SwitchStmt:
inner |= inBreakable
check.openScope(s)
check.initStmt(s.Init)
var x operand
tag := s.Tag
if tag == nil {
// use fake true tag value and position it at the opening { of the switch
ident := &ast.Ident{NamePos: s.Body.Lbrace, Name: "true"}
check.recordObject(ident, Universe.Lookup("true"))
tag = ident
}
check.expr(&x, tag)
check.multipleDefaults(s.Body.List)
// TODO(gri) check also correct use of fallthrough
seen := make(map[interface{}]token.Pos)
for i, c := range s.Body.List {
clause, _ := c.(*ast.CaseClause)
if clause == nil {
continue // error reported before
}
if x.mode != invalid {
for _, expr := range clause.List {
x := x // copy of x (don't modify original)
var y operand
check.expr(&y, expr)
if y.mode == invalid {
continue // error reported before
}
// If we have a constant case value, it must appear only
// once in the switch statement. Determine if there is a
// duplicate entry, but only report an error if there are
// no other errors.
var dupl token.Pos
var yy operand
if y.mode == constant {
// TODO(gri) This code doesn't work correctly for
// large integer, floating point, or
// complex values - the respective struct
// comparisons are shallow. Need to use a
// hash function to index the map.
dupl = seen[y.val]
seen[y.val] = y.pos()
yy = y // remember y
}
// TODO(gri) The convertUntyped call pair below appears in other places. Factor!
// Order matters: By comparing y against x, error positions are at the case values.
check.convertUntyped(&y, x.typ)
if y.mode == invalid {
continue // error reported before
}
check.convertUntyped(&x, y.typ)
if x.mode == invalid {
continue // error reported before
}
check.comparison(&y, &x, token.EQL)
if y.mode != invalid && dupl.IsValid() {
check.errorf(yy.pos(), "%s is duplicate case (previous at %s)",
&yy, check.fset.Position(dupl))
}
}
}
check.openScope(clause)
inner := inner
if i+1 < len(s.Body.List) {
inner |= fallthroughOk
}
check.stmtList(inner, clause.Body)
check.closeScope()
}
check.closeScope()
case *ast.TypeSwitchStmt:
inner |= inBreakable
check.openScope(s)
defer check.closeScope()
check.initStmt(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.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
lhs, _ = guard.Lhs[0].(*ast.Ident)
if lhs == nil {
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
check.recordObject(lhs, nil) // lhs variable is implicitly declared in each cause clause
rhs = guard.Rhs[0]
default:
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
// rhs must be of the form: expr.(type) and expr must be an interface
expr, _ := rhs.(*ast.TypeAssertExpr)
if expr == nil || expr.Type != nil {
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
var x operand
check.expr(&x, expr.X)
if x.mode == invalid {
return
}
xtyp, _ := x.typ.Underlying().(*Interface)
if xtyp == nil {
check.errorf(x.pos(), "%s is not an interface", &x)
return
}
check.multipleDefaults(s.Body.List)
var lhsVars []*Var // set of implicitly declared lhs variables
for _, s := range s.Body.List {
clause, _ := s.(*ast.CaseClause)
if clause == nil {
continue // error reported before
}
// Check each type in this type switch case.
var T Type
for _, expr := range clause.List {
T = check.typOrNil(expr)
if T != nil && T != Typ[Invalid] {
check.typeAssertion(expr.Pos(), &x, xtyp, T)
}
}
check.openScope(clause)
// If lhs exists, declare a corresponding variable in the case-local scope if necessary.
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)
// For the "declared but 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.declareObj(check.topScope, nil, obj)
check.recordImplicit(clause, obj)
}
check.stmtList(inner, clause.Body)
check.closeScope()
}
// If a lhs variable was declared but there were no case clauses, make sure
// we have at least one (dummy) 'unused' variable to force an error message.
if len(lhsVars) == 0 && lhs != nil {
lhsVars = []*Var{NewVar(lhs.Pos(), check.pkg, lhs.Name, x.typ)}
}
// Record lhs variables for this type switch, if any.
if len(lhsVars) > 0 {
check.lhsVarsList = append(check.lhsVarsList, lhsVars)
}
case *ast.SelectStmt:
inner |= inBreakable
check.multipleDefaults(s.Body.List)
for _, s := range s.Body.List {
clause, _ := s.(*ast.CommClause)
if clause == nil {
continue // error reported before
}
check.openScope(clause)
if s := clause.Comm; s != nil {
check.stmt(inner, s) // TODO(gri) check correctness of c.Comm (must be Send/RecvStmt)
}
check.stmtList(inner, clause.Body)
check.closeScope()
}
case *ast.ForStmt:
inner |= inBreakable | inContinuable
check.openScope(s)
check.initStmt(s.Init)
if s.Cond != nil {
var x operand
check.expr(&x, s.Cond)
if x.mode != invalid && !isBoolean(x.typ) {
check.errorf(s.Cond.Pos(), "non-boolean condition in for statement")
}
}
check.initStmt(s.Post)
check.stmt(inner, s.Body)
check.closeScope()
case *ast.RangeStmt:
inner |= inBreakable | inContinuable
check.openScope(s)
defer check.closeScope()
// check expression to iterate over
decl := s.Tok == token.DEFINE
var x operand
check.expr(&x, s.X)
if x.mode == invalid {
// if we don't have a declaration, we can still check the loop's body
// (otherwise we can't because we are missing the declared variables)
if !decl {
check.stmt(inner, s.Body)
}
return
}
// determine key/value types
var key, val Type
switch typ := x.typ.Underlying().(type) {
case *Basic:
if isString(typ) {
key = Typ[Int]
val = Typ[Rune]
}
case *Array:
key = Typ[Int]
val = typ.elt
case *Slice:
key = Typ[Int]
val = typ.elt
case *Pointer:
if typ, _ := typ.base.Underlying().(*Array); typ != nil {
key = Typ[Int]
val = typ.elt
}
case *Map:
key = typ.key
val = typ.elt
case *Chan:
key = typ.elt
val = Typ[Invalid]
if typ.dir&ast.RECV == 0 {
check.errorf(x.pos(), "cannot range over send-only channel %s", &x)
// ok to continue
}
if s.Value != nil {
check.errorf(s.Value.Pos(), "iteration over %s permits only one iteration variable", &x)
// ok to continue
}
}
if key == nil {
check.errorf(x.pos(), "cannot range over %s", &x)
// if we don't have a declaration, we can still check the loop's body
if !decl {
check.stmt(inner, s.Body)
}
return
}
// check assignment to/declaration of iteration variables
// (irregular assignment, cannot easily map to existing assignment checks)
if s.Key == nil {
check.invalidAST(s.Pos(), "range clause requires index iteration variable")
// ok to continue
}
// lhs expressions and initialization value (rhs) types
lhs := [2]ast.Expr{s.Key, s.Value}
rhs := [2]Type{key, val}
if decl {
// declaration; variable scope starts after the range clause
var idents []*ast.Ident
var vars []*Var
for i, lhs := range lhs {
if lhs == nil {
continue
}
// determine lhs variable
name := "_" // dummy, in case lhs is not an identifier
ident, _ := lhs.(*ast.Ident)
if ident != nil {
name = ident.Name
} else {
check.errorf(lhs.Pos(), "cannot declare %s", lhs)
}
idents = append(idents, ident)
obj := NewVar(lhs.Pos(), check.pkg, name, nil)
vars = append(vars, obj)
// initialize lhs variable
x.mode = value
x.expr = lhs // we don't have a better rhs expression to use here
x.typ = rhs[i]
check.initVar(obj, &x)
}
// declare variables
for i, ident := range idents {
check.declareObj(check.topScope, ident, vars[i])
}
} else {
// ordinary assignment
for i, lhs := range lhs {
if lhs == nil {
continue
}
x.mode = value
x.expr = lhs // we don't have a better rhs expression to use here
x.typ = rhs[i]
check.assignVar(lhs, &x)
}
}
check.stmt(inner, s.Body)
default:
check.errorf(s.Pos(), "invalid statement")
}
}
func (ctxt *context) getErrorInfo(v ssa.Value, member int, enclosingPos token.Pos, seen map[ssa.Value]bool) (result *errorInfo) {
if !enclosingPos.IsValid() {
panicf("getErrorInfo with invalid pos; %T %s", v, v)
}
// log.Printf("getErrorInfo[%d] %T %v {", member, v, v)
// defer func() {
// log.Printf("} -> %+v", result)
// }()
if seen[v] {
return &errorInfo{}
}
seen[v] = true
defer delete(seen, v)
if pos := v.Pos(); pos.IsValid() {
enclosingPos = pos
}
terminate := func() []errorTermination {
return []errorTermination{{
val: v,
pos: enclosingPos,
}}
}
switch v := v.(type) {
case *ssa.Call:
if member > 0 && member != v.Type().(*types.Tuple).Len()-1 {
log.Printf("error from non-final member of function")
return &errorInfo{unknown: terminate()}
}
return &errorInfo{nested: []*ssa.Call{v}}
case *ssa.ChangeInterface:
return ctxt.getErrorInfo(v.X, 0, enclosingPos, seen)
case *ssa.Extract:
return ctxt.getErrorInfo(v.Tuple, v.Index, enclosingPos, seen)
case *ssa.Field:
return &errorInfo{unknown: terminate()}
case *ssa.Index:
return &errorInfo{unknown: terminate()}
case *ssa.Lookup:
return &errorInfo{unknown: terminate()}
case *ssa.Const:
if v.Value != nil {
panicf("non-nil constant cannot make error, surely?")
}
return &errorInfo{}
case *ssa.MakeInterface:
// TODO look into components of v.X
return &errorInfo{nonNil: terminate()}
case *ssa.Next:
return &errorInfo{unknown: terminate()}
case *ssa.Parameter:
return &errorInfo{unknown: terminate()}
case *ssa.Phi:
var info errorInfo
for _, edge := range v.Edges {
info.add(ctxt.getErrorInfo(edge, member, enclosingPos, seen))
}
return &info
case *ssa.Select:
return &errorInfo{unknown: terminate()}
case *ssa.TypeAssert:
if v.CommaOk {
return &errorInfo{unknown: terminate()}
}
return ctxt.getErrorInfo(v.X, 0, enclosingPos, seen)
case *ssa.UnOp:
switch v.Op {
case token.ARROW:
return &errorInfo{unknown: terminate()}
case token.MUL:
if _, isGlobal := v.X.(*ssa.Global); isGlobal {
// Assume that if we're returning a global variable, it's a
// global non-nil error, such as os.ErrInvalid.
return &errorInfo{nonNil: terminate()}
}
return &errorInfo{unknown: terminate()}
default:
panicf("unexpected unary operator %s at %s", v, ctxt.lprog.Fset.Position(enclosingPos))
}
}
panicf("unexpected value found for error: %T; %v", v, v)
panic("not reached")
}
// blockBranches processes a block's statement list and returns the set of outgoing forward jumps.
// all is the scope of all declared labels, parent the set of labels declared in the immediately
// enclosing block, and lstmt is the labeled statement this block is associated with (or nil).
func (check *Checker) blockBranches(all *Scope, parent *block, lstmt *ast.LabeledStmt, list []ast.Stmt) []*ast.BranchStmt {
b := &block{parent: parent, lstmt: lstmt}
var (
varDeclPos token.Pos
fwdJumps, badJumps []*ast.BranchStmt
)
// All forward jumps jumping over a variable declaration are possibly
// invalid (they may still jump out of the block and be ok).
// recordVarDecl records them for the given position.
recordVarDecl := func(pos token.Pos) {
varDeclPos = pos
badJumps = append(badJumps[:0], fwdJumps...) // copy fwdJumps to badJumps
}
jumpsOverVarDecl := func(jmp *ast.BranchStmt) bool {
if varDeclPos.IsValid() {
for _, bad := range badJumps {
if jmp == bad {
return true
}
}
}
return false
}
blockBranches := func(lstmt *ast.LabeledStmt, list []ast.Stmt) {
// Unresolved forward jumps inside the nested block
// become forward jumps in the current block.
fwdJumps = append(fwdJumps, check.blockBranches(all, b, lstmt, list)...)
}
var stmtBranches func(ast.Stmt)
stmtBranches = func(s ast.Stmt) {
switch s := s.(type) {
case *ast.DeclStmt:
if d, _ := s.Decl.(*ast.GenDecl); d != nil && d.Tok == token.VAR {
recordVarDecl(d.Pos())
}
case *ast.LabeledStmt:
// declare non-blank label
if name := s.Label.Name; name != "_" {
lbl := NewLabel(s.Label.Pos(), check.pkg, name)
if alt := all.Insert(lbl); alt != nil {
check.softErrorf(lbl.pos, "label %s already declared", name)
check.reportAltDecl(alt)
// ok to continue
} else {
b.insert(s)
check.recordDef(s.Label, lbl)
}
// resolve matching forward jumps and remove them from fwdJumps
i := 0
for _, jmp := range fwdJumps {
if jmp.Label.Name == name {
// match
lbl.used = true
check.recordUse(jmp.Label, lbl)
if jumpsOverVarDecl(jmp) {
check.softErrorf(
jmp.Label.Pos(),
"goto %s jumps over variable declaration at line %d",
name,
check.fset.Position(varDeclPos).Line,
)
// ok to continue
}
} else {
// no match - record new forward jump
fwdJumps[i] = jmp
i++
}
}
fwdJumps = fwdJumps[:i]
lstmt = s
}
stmtBranches(s.Stmt)
case *ast.BranchStmt:
if s.Label == nil {
return // checked in 1st pass (check.stmt)
}
// determine and validate target
name := s.Label.Name
switch s.Tok {
case token.BREAK:
// spec: "If there is a label, it must be that of an enclosing
// "for", "switch", or "select" statement, and that is the one
// whose execution terminates."
valid := false
if t := b.enclosingTarget(name); t != nil {
switch t.Stmt.(type) {
case *ast.SwitchStmt, *ast.TypeSwitchStmt, *ast.SelectStmt, *ast.ForStmt, *ast.RangeStmt:
valid = true
}
}
if !valid {
check.errorf(s.Label.Pos(), "invalid break label %s", name)
return
}
case token.CONTINUE:
// spec: "If there is a label, it must be that of an enclosing
// "for" statement, and that is the one whose execution advances."
valid := false
if t := b.enclosingTarget(name); t != nil {
switch t.Stmt.(type) {
case *ast.ForStmt, *ast.RangeStmt:
valid = true
}
}
if !valid {
check.errorf(s.Label.Pos(), "invalid continue label %s", name)
return
}
case token.GOTO:
if b.gotoTarget(name) == nil {
// label may be declared later - add branch to forward jumps
fwdJumps = append(fwdJumps, s)
return
}
default:
check.invalidAST(s.Pos(), "branch statement: %s %s", s.Tok, name)
return
}
// record label use
obj := all.Lookup(name)
obj.(*Label).used = true
check.recordUse(s.Label, obj)
case *ast.AssignStmt:
if s.Tok == token.DEFINE {
recordVarDecl(s.Pos())
}
case *ast.BlockStmt:
blockBranches(lstmt, s.List)
case *ast.IfStmt:
stmtBranches(s.Body)
if s.Else != nil {
stmtBranches(s.Else)
}
case *ast.CaseClause:
blockBranches(nil, s.Body)
case *ast.SwitchStmt:
stmtBranches(s.Body)
case *ast.TypeSwitchStmt:
stmtBranches(s.Body)
case *ast.CommClause:
blockBranches(nil, s.Body)
case *ast.SelectStmt:
stmtBranches(s.Body)
case *ast.ForStmt:
stmtBranches(s.Body)
case *ast.RangeStmt:
stmtBranches(s.Body)
}
}
for _, s := range list {
stmtBranches(s)
}
return fwdJumps
}
// stmt typechecks statement s.
func (check *checker) stmt(s ast.Stmt) {
switch s := s.(type) {
case *ast.BadStmt, *ast.EmptyStmt:
// ignore
case *ast.DeclStmt:
d, _ := s.Decl.(*ast.GenDecl)
if d == nil || (d.Tok != token.CONST && d.Tok != token.TYPE && d.Tok != token.VAR) {
check.invalidAST(token.NoPos, "const, type, or var declaration expected")
return
}
if d.Tok == token.CONST {
check.assocInitvals(d)
}
check.decl(d)
case *ast.LabeledStmt:
// TODO(gri) anything to do with label itself?
check.stmt(s.Stmt)
case *ast.ExprStmt:
var x operand
used := false
switch e := unparen(s.X).(type) {
case *ast.CallExpr:
// function calls are permitted
used = true
// but some builtins are excluded
// (Caution: This evaluates e.Fun twice, once here and once
// below as part of s.X. This has consequences for
// check.register. Perhaps this can be avoided.)
check.expr(&x, e.Fun, nil, -1)
if x.mode != invalid {
if b, ok := x.typ.(*builtin); ok && !b.isStatement {
used = false
}
}
case *ast.UnaryExpr:
// receive operations are permitted
if e.Op == token.ARROW {
used = true
}
}
if !used {
check.errorf(s.Pos(), "%s not used", s.X)
// ok to continue
}
check.rawExpr(&x, s.X, nil, -1, false)
if x.mode == typexpr {
check.errorf(x.pos(), "%s is not an expression", &x)
}
case *ast.SendStmt:
var ch, x operand
check.expr(&ch, s.Chan, nil, -1)
check.expr(&x, s.Value, nil, -1)
if ch.mode == invalid || x.mode == invalid {
return
}
if tch, ok := underlying(ch.typ).(*Chan); !ok || tch.Dir&ast.SEND == 0 || !check.assignment(&x, tch.Elt) {
if x.mode != invalid {
check.invalidOp(ch.pos(), "cannot send %s to channel %s", &x, &ch)
}
}
case *ast.IncDecStmt:
var op token.Token
switch s.Tok {
case token.INC:
op = token.ADD
case token.DEC:
op = token.SUB
default:
check.invalidAST(s.TokPos, "unknown inc/dec operation %s", s.Tok)
return
}
var x operand
Y := &ast.BasicLit{ValuePos: s.X.Pos(), Kind: token.INT, Value: "1"} // use x's position
check.binary(&x, s.X, Y, op, -1)
if x.mode == invalid {
return
}
check.assign1to1(s.X, nil, &x, false, -1)
case *ast.AssignStmt:
switch s.Tok {
case token.ASSIGN, token.DEFINE:
if len(s.Lhs) == 0 {
check.invalidAST(s.Pos(), "missing lhs in assignment")
return
}
check.assignNtoM(s.Lhs, s.Rhs, s.Tok == token.DEFINE, -1)
default:
// assignment operations
if len(s.Lhs) != 1 || len(s.Rhs) != 1 {
check.errorf(s.TokPos, "assignment operation %s requires single-valued expressions", s.Tok)
return
}
// TODO(gri) make this conversion more efficient
var op token.Token
switch s.Tok {
case token.ADD_ASSIGN:
op = token.ADD
case token.SUB_ASSIGN:
op = token.SUB
case token.MUL_ASSIGN:
op = token.MUL
case token.QUO_ASSIGN:
op = token.QUO
case token.REM_ASSIGN:
op = token.REM
case token.AND_ASSIGN:
op = token.AND
case token.OR_ASSIGN:
op = token.OR
case token.XOR_ASSIGN:
op = token.XOR
case token.SHL_ASSIGN:
op = token.SHL
case token.SHR_ASSIGN:
op = token.SHR
case token.AND_NOT_ASSIGN:
op = token.AND_NOT
default:
check.invalidAST(s.TokPos, "unknown assignment operation %s", s.Tok)
return
}
var x operand
check.binary(&x, s.Lhs[0], s.Rhs[0], op, -1)
if x.mode == invalid {
return
}
check.assign1to1(s.Lhs[0], nil, &x, false, -1)
}
case *ast.GoStmt:
check.call(s.Call)
case *ast.DeferStmt:
check.call(s.Call)
case *ast.ReturnStmt:
sig := check.funcsig
if n := len(sig.Results); n > 0 {
// TODO(gri) should not have to compute lhs, named every single time - clean this up
lhs := make([]ast.Expr, n)
named := false // if set, function has named results
for i, res := range sig.Results {
if len(res.Name) > 0 {
// a blank (_) result parameter is a named result
named = true
}
name := ast.NewIdent(res.Name)
name.NamePos = s.Pos()
check.register(name, &Var{Name: res.Name, Type: res.Type}) // Pkg == nil
lhs[i] = name
}
if len(s.Results) > 0 || !named {
// TODO(gri) assignNtoM should perhaps not require len(lhs) > 0
check.assignNtoM(lhs, s.Results, false, -1)
}
} else if len(s.Results) > 0 {
check.errorf(s.Pos(), "no result values expected")
}
case *ast.BranchStmt:
// TODO(gri) implement this
case *ast.BlockStmt:
check.stmtList(s.List)
case *ast.IfStmt:
check.optionalStmt(s.Init)
var x operand
check.expr(&x, s.Cond, nil, -1)
if x.mode != invalid && !isBoolean(x.typ) {
check.errorf(s.Cond.Pos(), "non-boolean condition in if statement")
}
check.stmt(s.Body)
check.optionalStmt(s.Else)
case *ast.SwitchStmt:
check.optionalStmt(s.Init)
var x operand
tag := s.Tag
if tag == nil {
// use fake true tag value and position it at the opening { of the switch
ident := &ast.Ident{NamePos: s.Body.Lbrace, Name: "true"}
check.register(ident, Universe.Lookup("true"))
tag = ident
}
check.expr(&x, tag, nil, -1)
check.multipleDefaults(s.Body.List)
// TODO(gri) check also correct use of fallthrough
seen := make(map[interface{}]token.Pos)
for _, s := range s.Body.List {
clause, _ := s.(*ast.CaseClause)
if clause == nil {
continue // error reported before
}
if x.mode != invalid {
for _, expr := range clause.List {
x := x // copy of x (don't modify original)
var y operand
check.expr(&y, expr, nil, -1)
if y.mode == invalid {
continue // error reported before
}
// If we have a constant case value, it must appear only
// once in the switch statement. Determine if there is a
// duplicate entry, but only report an error if there are
// no other errors.
var dupl token.Pos
var yy operand
if y.mode == constant {
// TODO(gri) This code doesn't work correctly for
// large integer, floating point, or
// complex values - the respective struct
// comparisons are shallow. Need to use a
// hash function to index the map.
dupl = seen[y.val]
seen[y.val] = y.pos()
yy = y // remember y
}
// TODO(gri) The convertUntyped call pair below appears in other places. Factor!
// Order matters: By comparing y against x, error positions are at the case values.
check.convertUntyped(&y, x.typ)
if y.mode == invalid {
continue // error reported before
}
check.convertUntyped(&x, y.typ)
if x.mode == invalid {
continue // error reported before
}
check.comparison(&y, &x, token.EQL)
if y.mode != invalid && dupl.IsValid() {
check.errorf(yy.pos(), "%s is duplicate case (previous at %s)",
&yy, check.fset.Position(dupl))
}
}
}
check.stmtList(clause.Body)
}
case *ast.TypeSwitchStmt:
check.optionalStmt(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 *Var // lhs variable 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.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
ident, _ := guard.Lhs[0].(*ast.Ident)
if ident == nil {
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
lhs = check.lookup(ident).(*Var)
rhs = guard.Rhs[0]
default:
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
// rhs must be of the form: expr.(type) and expr must be an interface
expr, _ := rhs.(*ast.TypeAssertExpr)
if expr == nil || expr.Type != nil {
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
var x operand
check.expr(&x, expr.X, nil, -1)
if x.mode == invalid {
return
}
var T *Interface
if T, _ = underlying(x.typ).(*Interface); T == nil {
check.errorf(x.pos(), "%s is not an interface", &x)
return
}
check.multipleDefaults(s.Body.List)
for _, s := range s.Body.List {
clause, _ := s.(*ast.CaseClause)
if clause == nil {
continue // error reported before
}
// Check each type in this type switch case.
var typ Type
for _, expr := range clause.List {
typ = check.typOrNil(expr, false)
if typ != nil && typ != Typ[Invalid] {
if method, wrongType := missingMethod(typ, T); method != nil {
var msg string
if wrongType {
msg = "%s cannot have dynamic type %s (wrong type for method %s)"
} else {
msg = "%s cannot have dynamic type %s (missing method %s)"
}
check.errorf(expr.Pos(), msg, &x, typ, method.Name)
// ok to continue
}
}
}
// If lhs exists, set its type for each clause.
if lhs != nil {
// 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 || typ == nil {
typ = x.typ
}
lhs.Type = typ
}
check.stmtList(clause.Body)
}
// There is only one object (lhs) associated with a lhs identifier, but that object
// assumes different types for different clauses. Set it back to the type of the
// TypeSwitchGuard expression so that that variable always has a valid type.
if lhs != nil {
lhs.Type = x.typ
}
case *ast.SelectStmt:
check.multipleDefaults(s.Body.List)
for _, s := range s.Body.List {
clause, _ := s.(*ast.CommClause)
if clause == nil {
continue // error reported before
}
check.optionalStmt(clause.Comm) // TODO(gri) check correctness of c.Comm (must be Send/RecvStmt)
check.stmtList(clause.Body)
}
case *ast.ForStmt:
check.optionalStmt(s.Init)
if s.Cond != nil {
var x operand
check.expr(&x, s.Cond, nil, -1)
if x.mode != invalid && !isBoolean(x.typ) {
check.errorf(s.Cond.Pos(), "non-boolean condition in for statement")
}
}
check.optionalStmt(s.Post)
check.stmt(s.Body)
case *ast.RangeStmt:
// check expression to iterate over
decl := s.Tok == token.DEFINE
var x operand
check.expr(&x, s.X, nil, -1)
if x.mode == invalid {
// if we don't have a declaration, we can still check the loop's body
if !decl {
check.stmt(s.Body)
}
return
}
// determine key/value types
var key, val Type
switch typ := underlying(x.typ).(type) {
case *Basic:
if isString(typ) {
key = Typ[UntypedInt]
val = Typ[UntypedRune]
}
case *Array:
key = Typ[UntypedInt]
val = typ.Elt
case *Slice:
key = Typ[UntypedInt]
val = typ.Elt
case *Pointer:
if typ, _ := underlying(typ.Base).(*Array); typ != nil {
key = Typ[UntypedInt]
val = typ.Elt
}
case *Map:
key = typ.Key
val = typ.Elt
case *Chan:
key = typ.Elt
if typ.Dir&ast.RECV == 0 {
check.errorf(x.pos(), "cannot range over send-only channel %s", &x)
// ok to continue
}
if s.Value != nil {
check.errorf(s.Value.Pos(), "iteration over %s permits only one iteration variable", &x)
// ok to continue
}
}
if key == nil {
check.errorf(x.pos(), "cannot range over %s", &x)
// if we don't have a declaration, we can still check the loop's body
if !decl {
check.stmt(s.Body)
}
return
}
// check assignment to/declaration of iteration variables
// TODO(gri) The error messages/positions are not great here,
// they refer to the expression in the range clause.
// Should give better messages w/o too much code
// duplication (assignment checking).
x.mode = value
if s.Key != nil {
x.typ = key
x.expr = s.Key
check.assign1to1(s.Key, nil, &x, decl, -1)
} else {
check.invalidAST(s.Pos(), "range clause requires index iteration variable")
// ok to continue
}
if s.Value != nil {
x.typ = val
x.expr = s.Value
check.assign1to1(s.Value, nil, &x, decl, -1)
}
check.stmt(s.Body)
default:
check.errorf(s.Pos(), "invalid statement")
}
}