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go/types, types2: better error when trying to use ~ as bitwise operation 

When coming from C, the bitwise integer complement (bitwise negation)
operator is ~, but in Go it is ^. Report an error mentioning ^ when
~ is used with an integer operand.

Background: Some articles on the web claim that Go doesn't have a
bitwise complement operator.

Change-Id: I41185cae4a70d528754e44f42c13c013ed91bf27
Reviewed-on: https://go-review.googlesource.com/c/go/+/463747
Auto-Submit: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Robert Griesemer 2023-01-31 11:34:16 -08:00 committed by Gopher Robot
parent cda461bb79
commit 07dca0fe14
3 changed files with 34 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/cmd/compile/internal/types2/expr.go
View File

@ -178,7 +178,8 @@ func (check *Checker) unary(x *operand, e *syntax.Operation) {
return
}
switch e.Op {
op := e.Op
switch op {
case syntax.And:
// spec: "As an exception to the addressability
// requirement x may also be a composite literal."
@ -215,13 +216,17 @@ func (check *Checker) unary(x *operand, e *syntax.Operation) {
return
case syntax.Tilde:
// Provide a better error position and message than what check.op below could do.
check.error(e, UndefinedOp, "cannot use ~ outside of interface or type constraint")
x.mode = invalid
return
// Provide a better error position and message than what check.op below would do.
if !allInteger(x.typ) {
check.error(e, UndefinedOp, "cannot use ~ outside of interface or type constraint")
x.mode = invalid
return
}
check.error(e, UndefinedOp, "cannot use ~ outside of interface or type constraint (use ^ for bitwise complement)")
op = syntax.Xor
}
if !check.op(unaryOpPredicates, x, e.Op) {
if !check.op(unaryOpPredicates, x, op) {
x.mode = invalid
return
}
@ -235,7 +240,7 @@ func (check *Checker) unary(x *operand, e *syntax.Operation) {
if isUnsigned(x.typ) {
prec = uint(check.conf.sizeof(x.typ) * 8)
}
x.val = constant.UnaryOp(op2tok[e.Op], x.val, prec)
x.val = constant.UnaryOp(op2tok[op], x.val, prec)
x.expr = e
check.overflow(x)
return

20
src/go/types/expr.go
View File

@ -164,7 +164,9 @@ func (check *Checker) unary(x *operand, e *ast.UnaryExpr) {
if x.mode == invalid {
return
}
switch e.Op {
op := e.Op
switch op {
case token.AND:
// spec: "As an exception to the addressability
// requirement x may also be a composite literal."
@ -202,13 +204,17 @@ func (check *Checker) unary(x *operand, e *ast.UnaryExpr) {
return
case token.TILDE:
// Provide a better error position and message than what check.op below could do.
check.error(e, UndefinedOp, "cannot use ~ outside of interface or type constraint")
x.mode = invalid
return
// Provide a better error position and message than what check.op below would do.
if !allInteger(x.typ) {
check.error(e, UndefinedOp, "cannot use ~ outside of interface or type constraint")
x.mode = invalid
return
}
check.error(e, UndefinedOp, "cannot use ~ outside of interface or type constraint (use ^ for bitwise complement)")
op = token.XOR
}
if !check.op(unaryOpPredicates, x, e.Op) {
if !check.op(unaryOpPredicates, x, op) {
x.mode = invalid
return
}
@ -222,7 +228,7 @@ func (check *Checker) unary(x *operand, e *ast.UnaryExpr) {
if isUnsigned(x.typ) {
prec = uint(check.conf.sizeof(x.typ) * 8)
}
x.val = constant.UnaryOp(e.Op, x.val, prec)
x.val = constant.UnaryOp(op, x.val, prec)
x.expr = e
check.overflow(x, x.Pos())
return

9
src/internal/types/testdata/check/expr0.go vendored
View File

@ -24,12 +24,14 @@ var (
b11 = &b0
b12 = <-b0 /* ERROR "cannot receive" */
b13 = & & /* ERROR "cannot take address" */ b0
b14 = ~ /* ERROR "cannot use ~ outside of interface or type constraint" */ 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)
_ = ~ /* ERROR "cannot use ~ outside of interface or type constraint (use ^ for bitwise complement)" */ byte(0)
// int
i0 = 1
@ -51,6 +53,7 @@ var (
i16 = &i0
i17 = *i16
i18 = <-i16 /* ERROR "cannot receive" */
i19 = ~ /* ERROR "cannot use ~ outside of interface or type constraint (use ^ for bitwise complement)" */ i0
// uint
u0 = uint(1)
@ -73,6 +76,7 @@ var (
u17 = *u16
u18 = <-u16 /* ERROR "cannot receive" */
u19 = ^uint(0)
u20 = ~ /* ERROR "cannot use ~ outside of interface or type constraint (use ^ for bitwise complement)" */ u0
// float64
f0 = float64(1)
@ -94,6 +98,7 @@ var (
f16 = &f0
f17 = *u16
f18 = <-u16 /* ERROR "cannot receive" */
f19 = ~ /* ERROR "cannot use ~ outside of interface or type constraint" */ f0
// complex128
c0 = complex128(1)
@ -115,6 +120,7 @@ var (
c16 = &c0
c17 = *u16
c18 = <-u16 /* ERROR "cannot receive" */
c19 = ~ /* ERROR "cannot use ~ outside of interface or type constraint" */ c0
// string
s0 = "foo"
@ -126,6 +132,7 @@ var (
s6 = &s4
s7 = *s6
s8 = <-s7
s9 = ~ /* ERROR "cannot use ~ outside of interface or type constraint" */ s0
// channel
ch chan int
@ -145,6 +152,8 @@ var (
// ok is of type bool
ch11, myok = <-ch
_ mybool = myok /* ERRORx `cannot use .* in variable declaration` */
ch12 = ~ /* ERROR "cannot use ~ outside of interface or type constraint" */ ch
)
// address of composite literals