Add a Var abstraction in QuoteUtils

Author: biboudis

compiler/test/dotty/tools/dotc/BootstrappedOnlyCompilationTests.scala

@@ -120,8 +120,7 @@ class BootstrappedOnlyCompilationTests extends ParallelTesting {
     implicit val testGroup: TestGroup = TestGroup("runWithCompiler")
     aggregateTests(
       compileFilesInDir("tests/run-with-compiler", withCompilerOptions),
-      compileDir("tests/run-with-compiler-custom-args/tasty-interpreter", withCompilerOptions),
-      compileFile("tests/run-with-compiler-custom-args/staged-streams_1.scala", withCompilerOptions without "-Yno-deep-subtypes")
+      compileDir("tests/run-with-compiler-custom-args/tasty-interpreter", withCompilerOptions)
     ).checkRuns()
   }
 

library/src-bootstrapped/scala/quoted/util/QuoteUtils.scala

@@ -0,0 +1,24 @@
+package scala.quoted
+package util
+
+/** An abstraction for variable definition to use in a quoted program.
+ *  It decouples the operations of get and update, if needed to be spliced separately.
+ */
+sealed trait Var[T] {
+  def get given QuoteContext: Expr[T]
+  def update(x: Expr[T]) given QuoteContext: Expr[Unit]
+}
+
+object Var {
+  def apply[T: Type, U: Type](init: Expr[T])(body: Var[T] => Expr[U]) given QuoteContext: Expr[U] = '{
+    var x = $init
+    ${
+      body(
+        new Var[T] {
+          def get given QuoteContext: Expr[T] = 'x
+          def update(e: Expr[T]) given QuoteContext: Expr[Unit] = '{ x = $e }
+        }
+      )
+    }
+  }
+}

tests/run-with-compiler/staged-streams_1.check

@@ -0,0 +1,19 @@
+6
+
+12
+
+36
+
+2
+
+3
+
+7
+
+12
+
+15
+
+15
+
+72