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go/types: better error message for certain unaary/binary expression errors 

Fixes golang/go#11367.

Change-Id: Ic7f1bad51165685097c909fd18c245a57924cdc8
Reviewed-on: https://go-review.googlesource.com/11363
Reviewed-by: Alan Donovan <adonovan@google.com>
This commit is contained in:
Robert Griesemer 2015-06-23 12:26:56 -07:00
parent e9a746de6e
commit 6369699504
3 changed files with 20 additions and 6 deletions
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16
go/types/expr.go
View File

@ -79,7 +79,8 @@ func (check *Checker) op(m opPredicates, x *operand, op token.Token) bool {
return true
}
func (check *Checker) unary(x *operand, op token.Token) {
// The binary expression e may be nil. It's passed in for better error messages only.
func (check *Checker) unary(x *operand, e *ast.UnaryExpr, op token.Token) {
switch op {
case token.AND:
// spec: "As an exception to the addressability
@ -126,6 +127,9 @@ func (check *Checker) unary(x *operand, op token.Token) {
// Typed constants must be representable in
// their type after each constant operation.
if isTyped(typ) {
if e != nil {
x.expr = e // for better error message
}
check.representable(x, typ)
}
return
@ -722,7 +726,8 @@ var binaryOpPredicates = opPredicates{
token.LOR: isBoolean,
}
func (check *Checker) binary(x *operand, lhs, rhs ast.Expr, op token.Token) {
// The binary expression e may be nil. It's passed in for better error messages only.
func (check *Checker) binary(x *operand, e *ast.BinaryExpr, lhs, rhs ast.Expr, op token.Token) {
var y operand
check.expr(x, lhs)
@ -788,6 +793,9 @@ func (check *Checker) binary(x *operand, lhs, rhs ast.Expr, op token.Token) {
// Typed constants must be representable in
// their type after each constant operation.
if isTyped(typ) {
if e != nil {
x.expr = e // for better error message
}
check.representable(x, typ)
}
return
@ -1375,7 +1383,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
if x.mode == invalid {
goto Error
}
check.unary(x, e.Op)
check.unary(x, e, e.Op)
if x.mode == invalid {
goto Error
}
@ -1385,7 +1393,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
}
case *ast.BinaryExpr:
check.binary(x, e.X, e.Y, e.Op)
check.binary(x, e, e.X, e.Y, e.Op)
if x.mode == invalid {
goto Error
}

4
go/types/stmt.go
View File

@ -278,7 +278,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
}
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)
check.binary(&x, nil, s.X, Y, op)
if x.mode == invalid {
return
}
@ -310,7 +310,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
return
}
var x operand
check.binary(&x, s.Lhs[0], s.Rhs[0], op)
check.binary(&x, nil, s.Lhs[0], s.Rhs[0], op)
if x.mode == invalid {
return
}

6
go/types/testdata/expr0.src vendored
View File

@ -25,6 +25,12 @@ var (
b12 = <-b0 /* ERROR "cannot receive" */
b13 = & & /* ERROR "cannot take address" */ b0
// byte
_ = byte(0)
_ = byte(- /* ERROR "cannot convert" */ 1)
_ = - /* ERROR "-byte\(1\) \(constant -1 of type byte\) overflows byte" */ byte(1) // test for issue 11367
_ = byte /* ERROR "overflows byte" */ (0) - byte(1)
// int
i0 = 1
i1 int = i0