[cs] fix right expr casting on bitwise shifts

#8978

src/codegen/gencommon/castDetect.ml

@@ -71,6 +71,14 @@ struct
 		let current_ret_type = ref None in
 		let handle e tto tfrom = gen.ghandle_cast (gen.greal_type tto) (gen.greal_type tfrom) e in
 		let in_value = ref false in
+		let binop_right_expr_type op actual_type =
+			match op with
+			| OpShr | OpShl | OpUShr | OpAssignOp (OpShr | OpShl | OpUShr) ->
+				(match follow actual_type with
+				| TAbstract ({ a_path = (["cs"], "Int64") }, _) -> gen.gcon.basic.tint
+				| _ -> actual_type)
+			| _ -> actual_type
+		in
 
 		let rec run e =
 			let was_in_value = !in_value in
@@ -103,16 +111,19 @@ struct
 				(match field_access_esp gen (gen.greal_type tf.etype) (f) with
 					| FClassField(cl,params,_,_,is_static,actual_t,_) ->
 						let actual_t = if is_static then actual_t else apply_params cl.cl_params params actual_t in
+						let actual_t = binop_right_expr_type op actual_t in
 						let e1 = extract_expr (run e1) in
 						{ e with eexpr = TBinop(op, e1, handle (run e2) actual_t e2.etype); etype = e1.etype }
 					| _ ->
 						let e1 = extract_expr (run e1) in
-						{ e with eexpr = TBinop(op, e1, handle (run e2) e1.etype e2.etype); etype = e1.etype }
+						let actual_t = binop_right_expr_type op e2.etype in
+						{ e with eexpr = TBinop(op, e1, handle (run e2) e1.etype actual_t); etype = e1.etype }
 				)
 			| TBinop ( (Ast.OpAssign as op),e1,e2)
 			| TBinop ( (Ast.OpAssignOp _ as op),e1,e2) ->
 				let e1 = extract_expr (run e1) in
-				{ e with eexpr = TBinop(op, e1, handle (run e2) e1.etype e2.etype); etype = e1.etype }
+				let actual_t = binop_right_expr_type op e2.etype in
+				{ e with eexpr = TBinop(op, e1, handle (run e2) e1.etype actual_t); etype = e1.etype }
 			| _ -> Type.map_expr run e
 		in
 		run
@@ -1046,6 +1057,11 @@ let configure gen ?(overloads_cast_to_base = false) maybe_empty_t calls_paramete
 			| TCast( { eexpr = TCall( { eexpr = TIdent "__delegate__" } as local, [del] ) } as e2, _) ->
 				{ e with eexpr = TCast({ e2 with eexpr = TCall(local, [Type.map_expr run del]) }, None) }
 
+			| TBinop (OpAssignOp (Ast.OpShl | Ast.OpShr | Ast.OpUShr as op), e1, e2 ) ->
+				let e1 = run ~just_type:true e1 in
+				let e2 = handle (run e2) (gen.gcon.basic.tint) e2.etype in
+				let rett = binop_type op e e1 e2 in
+				{ e with eexpr = TBinop(OpAssignOp op, e1, e2); etype = rett.etype }
 			| TBinop ( (Ast.OpAssign | Ast.OpAssignOp _ as op), e1, e2 ) ->
 				let e1 = run ~just_type:true e1 in
 				let e2 = handle (run e2) e1.etype e2.etype in

tests/unit/src/unit/issues/Issue8978.hx

@@ -0,0 +1,25 @@
+package unit.issues;
+
+class Issue8978 extends unit.Test {
+#if cs
+	var classField:cs.types.Int64 = 1;
+	var anon:{field:cs.types.Int64} = {field:1};
+
+	function test() {
+		var local:cs.types.Int64 = 1;
+		var shift = 1;
+
+		classField <<= shift;
+		t(2 == classField);
+		t(1 == classField >> shift);
+
+		anon.field <<= shift;
+		t(2 == anon.field);
+		t(1 == anon.field >> shift);
+
+		local <<= shift;
+		t(2 == local);
+		t(1 == local >> shift);
+	}
+#end
+}