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author | Rob Findley <rfindley@google.com> | 2021-07-26 16:33:44 -0400 |
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committer | Robert Findley <rfindley@google.com> | 2021-07-27 00:15:55 +0000 |
commit | 33ff1559702388c57c45f9e6cd032f06e8c3c163 (patch) | |
tree | ea70eb9d690f80f24ed0c4e3d6610216cffde5c7 /src/go/types/expr.go | |
parent | 840e583ff340d22a6263a348922283e6d5cd2e31 (diff) | |
download | go-33ff1559702388c57c45f9e6cd032f06e8c3c163.tar.gz go-33ff1559702388c57c45f9e6cd032f06e8c3c163.zip |
go/types: preserve untyped constants on the RHS of a shift expression
CL 291316 fixed go/types to verify that untyped shift counts are
representable by uint, but as a side effect also converted their types
to uint.
Rearrange the logic to keep the check for representability, but not
actually convert untyped integer constants. Untyped non-integer
constants are still converted, to preserve the behavior of 1.16. This
behavior for non-integer types is a bug, filed as #47410.
Updates #47410
Fixes #47243
Change-Id: I5eab4aab35b97f932fccdee2d4a18623ee2ccad5
Reviewed-on: https://go-review.googlesource.com/c/go/+/337529
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Diffstat (limited to 'src/go/types/expr.go')
-rw-r--r-- | src/go/types/expr.go | 34 |
1 files changed, 25 insertions, 9 deletions
diff --git a/src/go/types/expr.go b/src/go/types/expr.go index 5c65fad447..58962e777b 100644 --- a/src/go/types/expr.go +++ b/src/go/types/expr.go @@ -778,32 +778,48 @@ 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." - // Provide a good error message for negative shift counts. + // Check that constants are representable by uint, but do not convert them + // (see also issue #47243). if y.mode == constant_ { + // Provide a good error message for negative shift counts. 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 } + + if isUntyped(y.typ) { + // Caution: Check for representability here, rather than in the switch + // below, because isInteger includes untyped integers (was bug #43697). + check.representable(y, Typ[Uint]) + if y.mode == invalid { + x.mode = invalid + return + } + } } - // Caution: Check for isUntyped first because isInteger includes untyped - // integers (was bug #43697). - if isUntyped(y.typ) { + // Check that RHS is otherwise at least of integer type. + switch { + case isInteger(y.typ): + if !isUnsigned(y.typ) && !check.allowVersion(check.pkg, 1, 13) { + check.invalidOp(y, _InvalidShiftCount, "signed shift count %s requires go1.13 or later", y) + x.mode = invalid + return + } + case isUntyped(y.typ): + // This is incorrect, but preserves pre-existing behavior. + // See also bug #47410. check.convertUntyped(y, Typ[Uint]) if y.mode == invalid { x.mode = invalid return } - } else if !isInteger(y.typ) { + default: check.invalidOp(y, _InvalidShiftCount, "shift count %s must be integer", y) x.mode = invalid return - } else if !isUnsigned(y.typ) && !check.allowVersion(check.pkg, 1, 13) { - check.invalidOp(y, _InvalidShiftCount, "signed shift count %s requires go1.13 or later", y) - x.mode = invalid - return } if x.mode == constant_ { |