// exprInternal contains the core of type checking of expressions.
// Must only be called by rawExpr.
//
func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
// make sure x has a valid state in case of bailout
// (was issue 5770)
x.mode = invalid
x.typ = Typ[Invalid]
switch e := e.(type) {
case *ast.BadExpr:
goto Error // error was reported before
case *ast.Ident:
check.ident(x, e, nil, nil)
case *ast.Ellipsis:
// ellipses are handled explicitly where they are legal
// (array composite literals and parameter lists)
check.error(e.Pos(), "invalid use of '...'")
goto Error
case *ast.BasicLit:
x.setConst(e.Kind, e.Value)
if x.mode == invalid {
check.invalidAST(e.Pos(), "invalid literal %v", e.Value)
goto Error
}
case *ast.FuncLit:
if sig, ok := check.typ(e.Type).(*Signature); ok {
// Anonymous functions are considered part of the
// init expression/func declaration which contains
// them: use existing package-level declaration info.
check.funcBody(check.decl, "", sig, e.Body)
x.mode = value
x.typ = sig
} else {
check.invalidAST(e.Pos(), "invalid function literal %s", e)
goto Error
}
case *ast.CompositeLit:
typ := hint
openArray := false
if e.Type != nil {
// [...]T array types may only appear with composite literals.
// Check for them here so we don't have to handle ... in general.
typ = nil
if atyp, _ := e.Type.(*ast.ArrayType); atyp != nil && atyp.Len != nil {
if ellip, _ := atyp.Len.(*ast.Ellipsis); ellip != nil && ellip.Elt == nil {
// We have an "open" [...]T array type.
// Create a new ArrayType with unknown length (-1)
// and finish setting it up after analyzing the literal.
typ = &Array{len: -1, elem: check.typ(atyp.Elt)}
openArray = true
}
}
if typ == nil {
typ = check.typ(e.Type)
}
if atyp, _ := typ.Underlying().(*Array); atyp != nil && atyp.len > -1 && int64(len(e.Elts)) != atyp.len {
if has, paths := check.hasZeroValue(atyp); !has {
check.errorHasZeroValuePaths(e.End(), paths)
}
}
}
if typ == nil {
// TODO(gri) provide better error messages depending on context
check.error(e.Pos(), "missing type in composite literal")
goto Error
}
switch typ, _ := deref(typ); utyp := typ.Underlying().(type) {
case *Struct:
if len(e.Elts) == 0 {
if has, paths := check.hasZeroValue(typ); !has {
check.errorHasZeroValuePaths(e.Rbrace, paths)
}
break
}
fields := utyp.fields
if _, ok := e.Elts[0].(*ast.KeyValueExpr); ok {
// all elements must have keys
visited := make([]bool, len(fields))
for _, e := range e.Elts {
kv, _ := e.(*ast.KeyValueExpr)
if kv == nil {
check.error(e.Pos(), "mixture of field:value and value elements in struct literal")
continue
}
key, _ := kv.Key.(*ast.Ident)
if key == nil {
check.errorf(kv.Pos(), "invalid field name %s in struct literal", kv.Key)
continue
}
i := fieldIndex(utyp.fields, check.pkg, key.Name)
if i < 0 {
check.errorf(kv.Pos(), "unknown field %s in struct literal", key.Name)
continue
}
fld := fields[i]
check.recordUse(key, fld)
// 0 <= i < len(fields)
if visited[i] {
check.errorf(kv.Pos(), "duplicate field name %s in struct literal", key.Name)
continue
}
visited[i] = true
check.expr(x, kv.Value)
etyp := fld.typ
check.assignment(x, etyp, "struct literal")
}
for i, v := range visited {
if !v {
field := utyp.Field(i)
if has, paths := check.hasZeroValue(field.Type()); !has {
for i, path := range paths {
paths[i] = append([]string{field.Name()}, path...)
}
check.errorHasZeroValuePaths(e.Rbrace, paths)
}
continue
}
}
} else {
// no element must have a key
for i, e := range e.Elts {
if kv, _ := e.(*ast.KeyValueExpr); kv != nil {
check.error(kv.Pos(), "mixture of field:value and value elements in struct literal")
continue
}
check.expr(x, e)
if i >= len(fields) {
check.error(x.pos(), "too many values in struct literal")
break // cannot continue
}
// i < len(fields)
fld := fields[i]
if !fld.Exported() && fld.pkg != check.pkg {
check.errorf(x.pos(), "implicit assignment to unexported field %s in %s literal", fld.name, typ)
continue
}
etyp := fld.typ
check.assignment(x, etyp, "struct literal")
}
if len(e.Elts) < len(fields) {
check.error(e.Rbrace, "too few values in struct literal")
// ok to continue
}
}
case *Array:
n := check.indexedElts(e.Elts, utyp.elem, utyp.len)
// if we have an "open" [...]T array, set the length now that we know it
if openArray {
utyp.len = n
}
case *Slice:
check.indexedElts(e.Elts, utyp.elem, -1)
case *Map:
visited := make(map[interface{}][]Type, len(e.Elts))
for _, e := range e.Elts {
kv, _ := e.(*ast.KeyValueExpr)
if kv == nil {
check.error(e.Pos(), "missing key in map literal")
continue
}
check.exprWithHint(x, kv.Key, utyp.key)
check.assignment(x, utyp.key, "map literal")
if x.mode == invalid {
continue
}
if x.mode == constant_ {
duplicate := false
// if the key is of interface type, the type is also significant when checking for duplicates
if _, ok := utyp.key.Underlying().(*Interface); ok {
for _, vtyp := range visited[x.val] {
if Identical(vtyp, x.typ) {
duplicate = true
break
}
}
visited[x.val] = append(visited[x.val], x.typ)
} else {
_, duplicate = visited[x.val]
visited[x.val] = nil
}
if duplicate {
check.errorf(x.pos(), "duplicate key %s in map literal", x.val)
continue
}
}
check.exprWithHint(x, kv.Value, utyp.elem)
check.assignment(x, utyp.elem, "map literal")
}
default:
// if utyp is invalid, an error was reported before
if utyp != Typ[Invalid] {
check.errorf(e.Pos(), "invalid composite literal type %s", typ)
goto Error
}
}
x.mode = value
x.typ = typ
case *ast.ParenExpr:
kind := check.rawExpr(x, e.X, nil)
x.expr = e
return kind
case *ast.SelectorExpr:
check.selector(x, e)
case *ast.IndexExpr:
check.expr(x, e.X)
if x.mode == invalid {
goto Error
}
valid := false
length := int64(-1) // valid if >= 0
switch typ := x.typ.Underlying().(type) {
case *Basic:
if isString(typ) {
valid = true
if x.mode == constant_ {
length = int64(len(constant.StringVal(x.val)))
}
// an indexed string always yields a byte value
// (not a constant) even if the string and the
// index are constant
x.mode = value
x.typ = universeByte // use 'byte' name
}
case *Array:
valid = true
length = typ.len
if x.mode != variable {
x.mode = value
}
x.typ = typ.elem
case *Pointer:
if typ, _ := typ.base.Underlying().(*Array); typ != nil {
valid = true
length = typ.len
x.mode = variable
x.typ = typ.elem
}
case *Slice:
valid = true
x.mode = variable
x.typ = typ.elem
case *Map:
var key operand
check.expr(&key, e.Index)
check.assignment(&key, typ.key, "map index")
if x.mode == invalid {
goto Error
}
x.mode = mapindex
x.typ = typ.elem
x.expr = e
return expression
}
if !valid {
check.invalidOp(x.pos(), "cannot index %s", x)
goto Error
}
if e.Index == nil {
check.invalidAST(e.Pos(), "missing index for %s", x)
goto Error
}
check.index(e.Index, length)
// ok to continue
case *ast.SliceExpr:
check.expr(x, e.X)
if x.mode == invalid {
goto Error
}
valid := false
length := int64(-1) // valid if >= 0
switch typ := x.typ.Underlying().(type) {
case *Basic:
if isString(typ) {
if e.Slice3 {
check.invalidOp(x.pos(), "3-index slice of string")
goto Error
}
valid = true
if x.mode == constant_ {
length = int64(len(constant.StringVal(x.val)))
}
// spec: "For untyped string operands the result
// is a non-constant value of type string."
if typ.kind == UntypedString {
x.typ = Typ[String]
}
}
case *Array:
valid = true
length = typ.len
if x.mode != variable {
check.invalidOp(x.pos(), "cannot slice %s (value not addressable)", x)
goto Error
}
x.typ = &Slice{elem: typ.elem}
case *Pointer:
if typ, _ := typ.base.Underlying().(*Array); typ != nil {
valid = true
length = typ.len
x.typ = &Slice{elem: typ.elem}
}
case *Slice:
valid = true
// x.typ doesn't change
}
if !valid {
check.invalidOp(x.pos(), "cannot slice %s", x)
goto Error
}
x.mode = value
// spec: "Only the first index may be omitted; it defaults to 0."
if e.Slice3 && (e.High == nil || e.Max == nil) {
check.error(e.Rbrack, "2nd and 3rd index required in 3-index slice")
goto Error
}
// check indices
var ind [3]int64
for i, expr := range []ast.Expr{e.Low, e.High, e.Max} {
x := int64(-1)
switch {
case expr != nil:
// The "capacity" is only known statically for strings, arrays,
// and pointers to arrays, and it is the same as the length for
// those types.
max := int64(-1)
if length >= 0 {
max = length + 1
}
if t, ok := check.index(expr, max); ok && t >= 0 {
x = t
}
case i == 0:
// default is 0 for the first index
x = 0
case length >= 0:
// default is length (== capacity) otherwise
x = length
}
ind[i] = x
}
// constant indices must be in range
// (check.index already checks that existing indices >= 0)
L:
for i, x := range ind[:len(ind)-1] {
if x > 0 {
for _, y := range ind[i+1:] {
if y >= 0 && x > y {
check.errorf(e.Rbrack, "invalid slice indices: %d > %d", x, y)
break L // only report one error, ok to continue
}
}
}
}
case *ast.TypeAssertExpr:
check.expr(x, e.X)
if x.mode == invalid {
goto Error
}
var xtyp *Interface
switch t := x.typ.Underlying().(type) {
case *Interface:
xtyp = t
case *Optional:
if IsInterface(t.Elem()) {
xtyp = t.Elem().Underlying().(*Interface)
}
}
if xtyp == nil {
check.invalidOp(x.pos(), "%s is not an interface", x)
goto Error
}
// x.(type) expressions are handled explicitly in type switches
if e.Type == nil {
check.invalidAST(e.Pos(), "use of .(type) outside type switch")
goto Error
}
T := check.typ(e.Type)
if T == Typ[Invalid] {
goto Error
}
check.typeAssertion(x.pos(), x, xtyp, T)
x.mode = commaok
x.typ = T
case *ast.CallExpr:
return check.call(x, e)
case *ast.StarExpr:
check.exprOrType(x, e.X)
switch x.mode {
case invalid:
goto Error
case typexpr:
x.typ = &Pointer{base: x.typ}
default:
if typ, ok := x.typ.Underlying().(*Pointer); ok {
x.mode = variable
x.typ = typ.base
} else {
check.invalidOp(x.pos(), "cannot indirect %s", x)
goto Error
}
}
case *ast.UnaryExpr:
check.expr(x, e.X)
if x.mode == invalid {
goto Error
}
check.unary(x, e, e.Op)
if x.mode == invalid {
goto Error
}
if e.Op == token.ARROW {
x.expr = e
return statement // receive operations may appear in statement context
}
case *ast.BinaryExpr:
check.binary(x, e, e.X, e.Y, e.Op)
if x.mode == invalid {
goto Error
}
case *ast.KeyValueExpr:
// key:value expressions are handled in composite literals
check.invalidAST(e.Pos(), "no key:value expected")
goto Error
case *ast.ArrayType, *ast.StructType, *ast.FuncType,
*ast.InterfaceType, *ast.MapType, *ast.ChanType,
*ast.OptionalType:
x.mode = typexpr
x.typ = check.typ(e)
// Note: rawExpr (caller of exprInternal) will call check.recordTypeAndValue
// even though check.typ has already called it. This is fine as both
// times the same expression and type are recorded. It is also not a
// performance issue because we only reach here for composite literal
// types, which are comparatively rare.
default:
panic(fmt.Sprintf("%s: unknown expression type %T", check.fset.Position(e.Pos()), e))
}
// everything went well
x.expr = e
return expression
Error:
x.mode = invalid
x.expr = e
return statement // avoid follow-up errors
}
