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Remove warning for discarded return value (#15718)

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Either this is valid code, or it is rejected by the language and backed
up by the spec. Since we now have `@mustuse`, this warning makes even
less sense to keep around as applying the attribute would make such code
an error in the future when/if it gets implemented for functions.
This commit is contained in:
Iain Buclaw 2023-10-22 09:04:27 +01:00 • committed by GitHub
parent 9a77d335ab
commit f4be7f6f7b
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2 changed files with 12 additions and 58 deletions
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35
compiler/src/dmd/sideeffect.d
View file

@ -269,41 +269,6 @@ bool discardValue(Expression e)
break;
}
case EXP.call:
/* Issue 3882: */
if (global.params.warnings != DiagnosticReporting.off && !global.gag)
{
CallExp ce = cast(CallExp)e;
if (e.type.ty == Tvoid)
{
/* Don't complain about calling void-returning functions with no side-effect,
* because purity and nothrow are inferred, and because some of the
* runtime library depends on it. Needs more investigation.
*
* One possible solution is to restrict this message to only be called in hierarchies that
* never call assert (and or not called from inside unittest blocks)
*/
}
else if (ce.e1.type)
{
Type t = ce.e1.type.toBasetype();
if (t.ty == Tdelegate)
t = (cast(TypeDelegate)t).next;
if (t.ty == Tfunction && (ce.f ? callSideEffectLevel(ce.f) : callSideEffectLevel(ce.e1.type)) > 0)
{
const(char)* s;
if (ce.f)
s = ce.f.toPrettyChars();
else if (ce.e1.op == EXP.star)
{
// print 'fp' if ce.e1 is (*fp)
s = (cast(PtrExp)ce.e1).e1.toChars();
}
else
s = ce.e1.toChars();
warning(e.loc, "calling `%s` without side effects discards return value of type `%s`; prepend a `cast(void)` if intentional", s, e.type.toChars());
}
}
}
return false;
case EXP.andAnd:
case EXP.orOr:

35
compiler/test/fail_compilation/fail3882.d
View file

@ -1,18 +1,17 @@
// REQUIRED_ARGS: -w
// PERMUTE_ARGS: -debug
/*
PERMUTE_ARGS: -debug
TEST_OUTPUT:
---
fail_compilation/fail3882.d(32): Error: `@mustuse` on functions is reserved for future use
fail_compilation/fail3882.d(33): Error: `@mustuse` on functions is reserved for future use
---
*/
import core.attribute;
/******************************************/
// https://issues.dlang.org/show_bug.cgi?id=3882
/*
TEST_OUTPUT:
---
fail_compilation/fail3882.d(23): Warning: calling `fail3882.strictlyPure!int.strictlyPure` without side effects discards return value of type `int`; prepend a `cast(void)` if intentional
fail_compilation/fail3882.d(27): Warning: calling `fp` without side effects discards return value of type `int`; prepend a `cast(void)` if intentional
---
*/
@safe pure nothrow T strictlyPure(T)(T x)
@mustuse @safe pure nothrow T strictlyPure(T)(T x)
{
return x*x;
}
@ -30,18 +29,8 @@ void main()
/******************************************/
// bugfix in TypeFunction::purityLevel
/*
TEST_OUTPUT:
---
fail_compilation/fail3882.d(48): Warning: calling `fail3882.f1` without side effects discards return value of type `int`; prepend a `cast(void)` if intentional
fail_compilation/fail3882.d(49): Warning: calling `fail3882.f2` without side effects discards return value of type `int`; prepend a `cast(void)` if intentional
Error: warnings are treated as errors
Use -wi if you wish to treat warnings only as informational.
---
*/
nothrow pure int f1(immutable(int)[] a) { return 0; }
nothrow pure int f2(immutable(int)* p) { return 0; }
@mustuse nothrow pure int f1(immutable(int)[] a) { return 0; }
@mustuse nothrow pure int f2(immutable(int)* p) { return 0; }
void test_bug()
{