Merge pull request #536 from scala/backport-lts-3.3-23590

Backport "Suppress warnings in comprehensions with 22+ binds" to 3.3 LTS

Author: tgodzik

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1629,7 +1629,19 @@ object desugar {
           val matchCheckMode =
             if (gen.checkMode == GenCheckMode.Check || gen.checkMode == GenCheckMode.CheckAndFilter) MatchCheck.IrrefutableGenFrom
             else MatchCheck.None
-          makeCaseLambda(CaseDef(gen.pat, EmptyTree, body) :: Nil, matchCheckMode)
+          val pat = gen.pat.match
+            case Tuple(pats) if pats.length > Definitions.MaxImplementedFunctionArity =>
+              /* The pattern case is a tupleXXL, because we have bound > 21 variables in the comprehension.
+               * In this case, we need to mark all the typed patterns as @unchecked, or get loads of warnings.
+               * Cf. warn test i23164.scala */
+              Tuple:
+                pats.map:
+                  case t @ Bind(name, tp @ Typed(id, tpt)) =>
+                    val annotated = Annotated(tpt, New(ref(defn.UncheckedAnnot.typeRef)))
+                    cpy.Bind(t)(name, cpy.Typed(tp)(id, annotated)).withMods(t.mods)
+                  case t => t
+            case _ => gen.pat
+          makeCaseLambda(CaseDef(pat, EmptyTree, body) :: Nil, matchCheckMode)
       }
 
       /** If `pat` is not an Identifier, a Typed(Ident, _), or a Bind, wrap

tests/warn/i23164.scala

@@ -0,0 +1,72 @@
+class T1[F[_]]
+class T2[F[_]]
+class T3[F[_]]
+class T4[F[_]]
+class T5[F[_]]
+class T6[F[_]]
+class T7[F[_]]
+class T8[F[_]]
+class T9[F[_]]
+class T10[F[_]]
+class T11[F[_]]
+class T12[F[_]]
+class T13[F[_]]
+class T14[F[_]]
+class T15[F[_]]
+class T16[F[_]]
+class T17[F[_]]
+class T18[F[_]]
+class T19[F[_]]
+class T20[F[_]]
+class T21[F[_]]
+class T22[F[_]]
+
+class Result[F[_]: {T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,T16,T17,T18,T19,T20,T21,T22}]
+
+val r = for
+  t1 <- Option(new T1[Option])
+  t2 <- Option(new T2[Option])
+  t3 <- Option(new T3[Option])
+  t4 <- Option(new T4[Option])
+  t5 <- Option(new T5[Option])
+  t6 <- Option(new T6[Option])
+  t7 <- Option(new T7[Option])
+  t8 <- Option(new T8[Option])
+  t9 <- Option(new T9[Option])
+  t10 <- Option(new T10[Option])
+  t11 <- Option(new T11[Option])
+  t12 <- Option(new T12[Option])
+  t13 <- Option(new T13[Option])
+  t14 <- Option(new T14[Option])
+  t15 <- Option(new T15[Option])
+  t16 <- Option(new T16[Option])
+  t17 <- Option(new T17[Option])
+  t18 <- Option(new T18[Option])
+  t19 <- Option(new T19[Option])
+  t20 <- Option(new T20[Option])
+  t21 <- Option(new T21[Option])
+  t22 <- Option(new T22[Option])
+  given T1[Option] = t1
+  given T2[Option] = t2
+  given T3[Option] = t3
+  given T4[Option] = t4
+  given T5[Option] = t5
+  given T6[Option] = t6
+  given T7[Option] = t7
+  given T8[Option] = t8
+  given T9[Option] = t9
+  given T10[Option] = t10
+  given T11[Option] = t11
+  given T12[Option] = t12
+  given T13[Option] = t13
+  given T14[Option] = t14
+  given T15[Option] = t15
+  given T16[Option] = t16
+  given T17[Option] = t17
+  given T18[Option] = t18
+  given T19[Option] = t19
+  given T20[Option] = t20
+  given T21[Option] = t21
+  given T22[Option] = t22
+  result <- Option(new Result[Option])
+yield result