Allow non-hot values in SeqLiterals

Closes #14460, #14751

Do not ensure that elements in a SeqLiteral are Hot.

Review by @liufengyun

Author: Xavientois

compiler/src/dotty/tools/dotc/transform/init/Semantic.scala

@@ -1234,9 +1234,9 @@ object Semantic {
 
       case SeqLiteral(elems, elemtpt) =>
         val ress = elems.map { elem =>
-          eval(elem, thisV, klass).ensureHot("May only use initialized value as method arguments", elem)
+          eval(elem, thisV, klass)
         }
-        Result(Hot, ress.flatMap(_.errors))
+        Result(ress.map(_.value).join, ress.flatMap(_.errors))
 
       case Inlined(call, bindings, expansion) =>
         val trace1 = trace.add(expr)

tests/init/neg/enum-desugared.check

@@ -1,18 +1,9 @@
--- Error: tests/init/neg/enum-desugared.scala:17:15 --------------------------------------------------------------------
-17 |    Array(this.LazyErrorId, this.NoExplanationID) // error // error
-   |          ^^^^^^^^^^^^^^^^
-   |          Cannot prove that the value is fully initialized. May only use initialized value as method arguments.
+-- Error: tests/init/neg/enum-desugared.scala:17:10 --------------------------------------------------------------------
+17 |    Array(this.LazyErrorId, this.NoExplanationID) // error
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |          Cannot prove that the value is fully initialized. Only initialized values may be used as arguments.
    |
    |          The unsafe promotion may cause the following problem:
    |          Calling the external method method name may cause initialization errors. Calling trace:
-   |           -> Array(this.LazyErrorId, this.NoExplanationID) // error // error	[ enum-desugared.scala:17 ]
+   |           -> Array(this.LazyErrorId, this.NoExplanationID) // error	[ enum-desugared.scala:17 ]
    |            -> override def productPrefix: String = this.name()	[ enum-desugared.scala:29 ]
--- Error: tests/init/neg/enum-desugared.scala:17:33 --------------------------------------------------------------------
-17 |    Array(this.LazyErrorId, this.NoExplanationID) // error // error
-   |                            ^^^^^^^^^^^^^^^^^^^^
-   |           Cannot prove that the value is fully initialized. May only use initialized value as method arguments.
-   |
-   |           The unsafe promotion may cause the following problem:
-   |           Calling the external method method ordinal may cause initialization errors. Calling trace:
-   |            -> Array(this.LazyErrorId, this.NoExplanationID) // error // error	[ enum-desugared.scala:17 ]
-   |             -> def errorNumber: Int = this.ordinal() - 2	[ enum-desugared.scala:8 ]

tests/init/neg/enum-desugared.scala

@@ -14,7 +14,7 @@ object ErrorMessageID {
   final val NoExplanationID = $new(1, "NoExplanationID")
 
   private[this] val $values: Array[ErrorMessageID] =
-    Array(this.LazyErrorId, this.NoExplanationID) // error // error
+    Array(this.LazyErrorId, this.NoExplanationID) // error
 
   def values: Array[ErrorMessageID] = $values.clone()
 

tests/init/neg/enum.check

@@ -1,7 +1,7 @@
 -- Error: tests/init/neg/enum.scala:4:8 --------------------------------------------------------------------------------
 4 |        NoExplanationID // error
   |        ^
-  |        Cannot prove that the value is fully initialized. May only use initialized value as method arguments.
+  |        Cannot prove that the value is fully initialized. Only initialized values may be used as arguments.
   |
   |        The unsafe promotion may cause the following problem:
   |        Calling the external method method name may cause initialization errors. Calling trace:

tests/init/neg/leak-warm.check

@@ -1,8 +1,4 @@
 -- Error: tests/init/neg/leak-warm.scala:18:26 -------------------------------------------------------------------------
-18 |    val l: List[A] = List(c, d) // error // error
-   |                          ^
-   |           Cannot prove that the value is fully initialized. May only use initialized value as method arguments.
--- Error: tests/init/neg/leak-warm.scala:18:29 -------------------------------------------------------------------------
-18 |    val l: List[A] = List(c, d) // error // error
-   |                             ^
-   |           Cannot prove that the value is fully initialized. May only use initialized value as method arguments.
+18 |    val l: List[A] = List(c, d) // error
+   |                          ^^^^
+   |             Cannot prove that the value is fully initialized. Only initialized values may be used as arguments.

tests/init/neg/leak-warm.scala

@@ -15,6 +15,6 @@ object leakWarm {
     }
     val c = new C(1, 2)
     val d = new D(3, 4)
-    val l: List[A] = List(c, d) // error // error
+    val l: List[A] = List(c, d) // error
     val l2 = l.map(_.m())
 }