Fix #5386: Generate a synthetic val def and then apply the unary operator

compiler/src/dotty/tools/dotc/transform/InterceptedMethods.scala

@@ -9,6 +9,7 @@ import dotty.tools.dotc.core.Names.TermName
 import dotty.tools.dotc.core.StdNames._
 import dotty.tools.dotc.core.Symbols._
 import dotty.tools.dotc.core.Types._
+import dotty.tools.dotc.core.NameKinds._
 import dotty.tools.dotc.transform.MegaPhase.MiniPhase
 
 object InterceptedMethods {
@@ -22,6 +23,7 @@ object InterceptedMethods {
   * - `x.##` for ## in Any becomes calls to ScalaRunTime.hash,
   *     using the most precise overload available
   * - `x.getClass` for getClass in primitives becomes `x.getClass` with getClass in class Object.
+  * - `!{...;true}` becomes val tmp = {...;true};!tmp (similar to other primitives/unary ops)
   */
 class InterceptedMethods extends MiniPhase {
   import tpd._
@@ -45,6 +47,16 @@ class InterceptedMethods extends MiniPhase {
       ctx.log(s"$phaseName rewrote $tree to $rewritten")
       rewritten
     }
+    // if the qualifier is constant folded then its type doesn't have a symbol
+    // in case a unary operator is applied to a block (potentially containing impure expressions)
+    // we create a synthetic variable and then apply the operator
+    else if (!tree.qualifier.symbol.exists && tree.name.startsWith(nme.UNARY_PREFIX.toString)) {
+      val tempDef = SyntheticValDef(UniqueName.fresh().toTermName, tree.qualifier)
+      val rewritten = Block(tempDef :: Nil, ref(tempDef.symbol).select(tree.name))
+      ctx.log(s"$phaseName rewrote $tree to $rewritten")
+
+      rewritten
+    }
     else tree
   }
 

tests/pos/i5386.scala

@@ -0,0 +1,23 @@
+object Test {
+  ~{
+    println("!")
+    1
+  }
+
+  +{
+    println("!")
+    1
+  }
+
+  -{
+    println("!")
+    1
+  }
+
+  !{
+    println("!")
+    true
+  }
+
+  !(try true finally{()})
+}