Do not handle null in StringToExpr

[Cherry-picked 2e3c803]

Author: mbovel

compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala

@@ -2420,7 +2420,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
     object StringConstant extends StringConstantModule:
       def apply(x: String): StringConstant =
-        require(x != null, "StringConstant cannot be null")
+        require(x != null, "value of StringConstant cannot be `null`")
         // A `null` constant must be represented as a `NullConstant`, c.f. a
         // constant with `tag == NullTag`, which is not a `StringConstant`.
         // See issue 23008.

library/src/scala/quoted/Quotes.scala

@@ -3556,7 +3556,10 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
 
     /** Methods of the module object `val StringConstant` */
     trait StringConstantModule { this: StringConstant.type =>
-      /** Create a constant String value */
+      /** Create a constant String value
+       *
+       *  @throw `IllegalArgumentException` if the argument is `null`
+       */
       def apply(x: String): StringConstant
       /** Match String value constant and extract its value */
       def unapply(constant: StringConstant): Some[String]

library/src/scala/quoted/ToExpr.scala

@@ -77,13 +77,7 @@ object ToExpr {
   given StringToExpr[T <: String]: ToExpr[T] with {
     def apply(x: T)(using Quotes) =
       import quotes.reflect.*
-      val literal =
-        if (x: Any) == null then
-          // Can happen if called from code without `-Yexplicit-nulls`.
-          Literal(NullConstant())
-        else
-          Literal(StringConstant(x))
-      literal.asExpr.asInstanceOf[Expr[T]]
+      Literal(StringConstant(x)).asExpr.asInstanceOf[Expr[T]]
   }
 
   /** Default implementation of `ToExpr[Class[T]]` */

tests/neg-macros/i23008.check

@@ -0,0 +1,21 @@
+
+-- Error: tests/neg-macros/i23008/Test_2.scala:1:24 --------------------------------------------------------------------
+1 |@main def Test = Macros.buildString // error
+  |                 ^^^^^^^^^^^^^^^^^^
+  |                 Exception occurred while executing macro expansion.
+  |                 java.lang.IllegalArgumentException: requirement failed: value of StringConstant cannot be `null`
+  |                 	at scala.Predef$.require(Predef.scala:337)
+  |                 	at scala.quoted.runtime.impl.QuotesImpl$reflect$StringConstant$.apply(QuotesImpl.scala:2533)
+  |                 	at scala.quoted.runtime.impl.QuotesImpl$reflect$StringConstant$.apply(QuotesImpl.scala:2532)
+  |                 	at scala.quoted.ToExpr$StringToExpr.apply(ToExpr.scala:80)
+  |                 	at scala.quoted.ToExpr$StringToExpr.apply(ToExpr.scala:78)
+  |                 	at scala.quoted.Expr$.apply(Expr.scala:70)
+  |                 	at Macros$.buildStringCode(Macro_1.scala:9)
+  |
+  |---------------------------------------------------------------------------------------------------------------------
+  |Inline stack trace
+  |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+  |This location contains code that was inlined from Macro_1.scala:4
+4 |  inline def buildString = ${buildStringCode}
+  |                           ^^^^^^^^^^^^^^^^^^
+   ---------------------------------------------------------------------------------------------------------------------

tests/run-macros/i23008/Macros_1.scala renamed to tests/neg-macros/i23008/Macro_1.scala

@@ -6,7 +6,6 @@ object Macros {
   def buildStringCode(using Quotes): Expr[String] = {
     import quotes.reflect.*
     val str: String = null
-    val exprString = Expr(str)
-    Expr(exprString.show)
+    Expr(str)
   }
 }

tests/neg-macros/i23008/Test_2.scala

@@ -0,0 +1 @@
+@main def Test = Macros.buildString // error