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>
diff --git a/src/cmd/compile/internal/types2/expr.go b/src/cmd/compile/internal/types2/expr.go
index 0433f8a..472e30a 100644
--- a/src/cmd/compile/internal/types2/expr.go
+++ b/src/cmd/compile/internal/types2/expr.go
@@ -178,7 +178,8 @@
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 @@
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 @@
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
diff --git a/src/go/types/expr.go b/src/go/types/expr.go
index b85a2c7..f09a29b 100644
--- a/src/go/types/expr.go
+++ b/src/go/types/expr.go
@@ -164,7 +164,9 @@
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 @@
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 @@
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
diff --git a/src/internal/types/testdata/check/expr0.go b/src/internal/types/testdata/check/expr0.go
index 552bd8f..eba991e 100644
--- a/src/internal/types/testdata/check/expr0.go
+++ b/src/internal/types/testdata/check/expr0.go
@@ -24,12 +24,14 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
// 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
