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Assignement in condition warning #12250

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a1b5609
Assignement in condition warning
RblSb Jun 1, 2025
d215498
version without parentheses
RblSb Jun 1, 2025
5636c6b
sub-warning
RblSb Nov 22, 2025
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11 changes: 11 additions & 0 deletions src-json/warning.json
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,17 @@
"doc": "A local variable might be used before being assigned a value",
"parent": "WTyper"
},
{
"name": "WConditionAssign",
"doc": "Using the result of an assignment as a condition",
"parent": "WTyper"
},
{
"name": "WConditionAssignBool",
"doc": "Using the result of an bool assignment as a condition",
"parent": "WTyper",
"enabled": false
},
{
"name": "WVarShadow",
"doc": "A local variable hides another by using the same name",
Expand Down
31 changes: 31 additions & 0 deletions src/typing/typer.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -1474,8 +1474,37 @@ and make_if_then_else ctx e0 e1 e2 with_type p =
let e2 = cast e2 in
mk (TIf (e0,e1,Some e2)) t p

and warn_assign_in_condition ctx cond =
let rec is_assign e =
let e = Texpr.skip e in
match e.eexpr with
| TBinop (OpAssign, lhs, rhs) ->
let lt = follow lhs.etype in
let is_bool = ExtType.is_bool lt in
if lt == t_dynamic || is_bool then
let rt = follow rhs.etype in
let is_rhs_bool = ExtType.is_bool rt in
let is_null = match (Texpr.skip rhs).eexpr with | TConst TNull -> true | _ -> false in
if is_rhs_bool && not is_null then
warning ctx WConditionAssignBool "Using the result of an bool assignment as a condition" e.epos
else
warning ctx WConditionAssign "Using the result of an assignment as a condition" e.epos
| TBinop ((OpBoolAnd | OpBoolOr), e1, e2) ->
is_assign e1;
is_assign e2;
| TBlock el ->
let rec last = function
| [] -> ()
| [e] -> is_assign e;
| _ :: rest -> last rest in
last el;
| _ -> ()
in
if not ctx.f.untyped then is_assign cond;

and type_if ctx e e1 e2 with_type is_ternary p =
let e = type_expr ctx e WithType.value in
warn_assign_in_condition ctx e;
if is_ternary then begin match e.eexpr with
| TConst TNull -> raise_typing_error "Cannot use null as ternary condition" e.epos
| _ -> ()
Expand Down Expand Up @@ -1839,6 +1868,7 @@ and type_expr ?(mode=MGet) ctx (e,p) (with_type:WithType.t) =
| EWhile (cond,e,NormalWhile) ->
let old_loop = ctx.e.in_loop in
let cond = type_expr ctx cond WithType.value in
warn_assign_in_condition ctx cond;
let cond = AbstractCast.cast_or_unify ctx ctx.t.tbool cond p in
ctx.e.in_loop <- true;
let e = type_expr ctx (Expr.ensure_block e) WithType.NoValue in
Expand All @@ -1850,6 +1880,7 @@ and type_expr ?(mode=MGet) ctx (e,p) (with_type:WithType.t) =
let e = type_expr ctx (Expr.ensure_block e) WithType.NoValue in
ctx.e.in_loop <- old_loop;
let cond = type_expr ctx cond WithType.value in
warn_assign_in_condition ctx cond;
let cond = AbstractCast.cast_or_unify ctx ctx.t.tbool cond cond.epos in
mk (TWhile (cond,e,DoWhile)) ctx.t.tvoid p
| ESwitch (e1,cases,def) ->
Expand Down
28 changes: 28 additions & 0 deletions tests/misc/projects/Issue8634/Main2.hx
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Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
class Main2 {
static function main() {
var foo = false;
var foo2 = false;

var value = (foo = foo2) ? true : false;
if (foo = foo2) {}
if (foo = true) {}
if (foo = null) {} // WConditionAssign
if ({123; foo = true;}) {}

while (foo = false) {}
do {} while (foo = false);

if ((foo = null) && (foo = true)) {}
if ((foo = null) && ((foo = true) && (foo = true))) {}

var dyn:Dynamic = false;
var dyn2:Dynamic = null;
if (dyn = 1) {}
if (dyn = dyn2) {}
if (dyn = null) {}
if (dyn = false) {} // WConditionAssignBool

// no warning
if ({foo = true; true;}) {}
}
}
4 changes: 4 additions & 0 deletions tests/misc/projects/Issue8634/compile-fail2.hxml
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@@ -0,0 +1,4 @@
--main Main2
--interp
-w +WConditionAssignBool
-D message.reporting=classic
16 changes: 16 additions & 0 deletions tests/misc/projects/Issue8634/compile-fail2.hxml.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
Main2.hx:6: characters 16-26 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:7: characters 7-17 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:8: characters 7-17 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:9: characters 7-17 : Warning : (WConditionAssign) Using the result of an assignment as a condition
Main2.hx:10: characters 13-23 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:12: characters 10-21 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:13: characters 16-27 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:15: characters 8-18 : Warning : (WConditionAssign) Using the result of an assignment as a condition
Main2.hx:15: characters 24-34 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:16: characters 8-18 : Warning : (WConditionAssign) Using the result of an assignment as a condition
Main2.hx:16: characters 25-35 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:16: characters 41-51 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
Main2.hx:20: characters 7-14 : Warning : (WConditionAssign) Using the result of an assignment as a condition
Main2.hx:21: characters 7-17 : Warning : (WConditionAssign) Using the result of an assignment as a condition
Main2.hx:22: characters 7-17 : Warning : (WConditionAssign) Using the result of an assignment as a condition
Main2.hx:23: characters 7-18 : Warning : (WConditionAssignBool) Using the result of an bool assignment as a condition
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