From a7e9b4b94804a1fbefc0c012ec510f4ee0837ffa Mon Sep 17 00:00:00 2001 From: Rob Findley Date: Thu, 11 Feb 2021 10:17:39 -0500 Subject: [dev.regabi] go/types: untyped shift counts must fit into uint This is a port of CL 283872 to go/types. It differs from that CL only in added error codes. For #43697 Change-Id: I62277834cef1c0359bcf2c6ee4388731babbc855 Reviewed-on: https://go-review.googlesource.com/c/go/+/291316 Trust: Robert Findley Trust: Robert Griesemer Run-TryBot: Robert Findley TryBot-Result: Go Bot Reviewed-by: Robert Griesemer --- src/go/types/expr.go | 26 ++++++++++++++++++-------- src/go/types/testdata/shifts.src | 12 +++++++----- 2 files changed, 25 insertions(+), 13 deletions(-) diff --git a/src/go/types/expr.go b/src/go/types/expr.go index 1a3c486af7..7f8aaed411 100644 --- a/src/go/types/expr.go +++ b/src/go/types/expr.go @@ -730,14 +730,14 @@ func (check *Checker) comparison(x, y *operand, op token.Token) { // If e != nil, it must be the shift expression; it may be nil for non-constant shifts. func (check *Checker) shift(x, y *operand, e ast.Expr, op token.Token) { - untypedx := isUntyped(x.typ) + // TODO(gri) This function seems overly complex. Revisit. var xval constant.Value if x.mode == constant_ { xval = constant.ToInt(x.val) } - if isInteger(x.typ) || untypedx && xval != nil && xval.Kind() == constant.Int { + if isInteger(x.typ) || isUntyped(x.typ) && xval != nil && xval.Kind() == constant.Int { // The lhs is of integer type or an untyped constant representable // as an integer. Nothing to do. } else { @@ -749,16 +749,26 @@ func (check *Checker) shift(x, y *operand, e ast.Expr, op token.Token) { // spec: "The right operand in a shift expression must have integer type // or be an untyped constant representable by a value of type uint." - switch { - case isInteger(y.typ): - // nothing to do - case isUntyped(y.typ): + + // Provide a good error message for negative shift counts. + if y.mode == constant_ { + yval := constant.ToInt(y.val) // consider -1, 1.0, but not -1.1 + if yval.Kind() == constant.Int && constant.Sign(yval) < 0 { + check.invalidOp(y, _InvalidShiftCount, "negative shift count %s", y) + x.mode = invalid + return + } + } + + // Caution: Check for isUntyped first because isInteger includes untyped + // integers (was bug #43697). + if isUntyped(y.typ) { check.convertUntyped(y, Typ[Uint]) if y.mode == invalid { x.mode = invalid return } - default: + } else if !isInteger(y.typ) { check.invalidOp(y, _InvalidShiftCount, "shift count %s must be integer", y) x.mode = invalid return @@ -816,7 +826,7 @@ func (check *Checker) shift(x, y *operand, e ast.Expr, op token.Token) { } // non-constant shift with constant lhs - if untypedx { + if isUntyped(x.typ) { // spec: "If the left operand of a non-constant shift // expression is an untyped constant, the type of the // constant is what it would be if the shift expression diff --git a/src/go/types/testdata/shifts.src b/src/go/types/testdata/shifts.src index c9a38ae169..4d3c59a50f 100644 --- a/src/go/types/testdata/shifts.src +++ b/src/go/types/testdata/shifts.src @@ -20,7 +20,7 @@ func shifts0() { // This depends on the exact spec wording which is not // done yet. // TODO(gri) revisit and adjust when spec change is done - _ = 1<<- /* ERROR "truncated to uint" */ 1.0 + _ = 1<<- /* ERROR "negative shift count" */ 1.0 _ = 1<<1075 /* ERROR "invalid shift" */ _ = 2.0<<1 _ = 1<<1.0 @@ -60,11 +60,13 @@ func shifts1() { _ uint = 1 << u _ float32 = 1 /* ERROR "must be integer" */ << u - // for issue 14822 + // issue #14822 + _ = 1<<( /* ERROR "overflows uint" */ 1<<64) _ = 1<<( /* ERROR "invalid shift count" */ 1<<64-1) - _ = 1<<( /* ERROR "invalid shift count" */ 1<<64) - _ = u<<(1<<63) // valid - _ = u<<(1<<64) // valid + + // issue #43697 + _ = u<<( /* ERROR "overflows uint" */ 1<<64) + _ = u<<(1<<64-1) ) } -- cgit v1.2.3-54-g00ecf