Restore ambigious-named-tuple-assignment migration rewrite

Author: WojciechMazur

compiler/src/dotty/tools/dotc/reporting/messages.scala

@@ -3362,7 +3362,7 @@ end QuotedTypeMissing
 
 final class DeprecatedAssignmentSyntax(key: Name, value: untpd.Tree)(using Context) extends SyntaxMsg(DeprecatedAssignmentSyntaxID):
   override protected def msg(using Context): String =
-    i"""Deprecated syntax: in the future it would be interpreted as a named tuple with one element,
+    i"""Ambiguous syntax: this is interpreted as a named tuple with one element,
       |not as an assignment.
       |
       |To assign a value, use curly braces: `{${key} = ${value}}`."""

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -3500,19 +3500,22 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
  /** Checks if `tree` is a named tuple with one element that could be
   *  interpreted as an assignment, such as `(x = 1)`. If so, issues a warning.
   */
-  def checkDeprecatedAssignmentSyntax(tree: untpd.Tuple)(using Context): Unit =
-    tree.trees match
-      case List(NamedArg(name, value)) =>
+  def checkDeprecatedAssignmentSyntax(tree: untpd.Tuple | untpd.Parens)(using Context): Unit =
+    val assignmentArgs = tree match {
+      case untpd.Tuple(List(NamedArg(name, value))) =>
         val tmpCtx = ctx.fresh.setNewTyperState()
         typedAssign(untpd.Assign(untpd.Ident(name), value), WildcardType)(using tmpCtx)
-        if !tmpCtx.reporter.hasErrors then
-          // If there are no errors typing the above, then the named tuple is
-          // ambiguous and we issue a warning.
-          report.migrationWarning(DeprecatedAssignmentSyntax(name, value), tree.srcPos)
-          if MigrationVersion.AmbiguousNamedTupleSyntax.needsPatch then
-            patch(tree.source, Span(tree.span.start, tree.span.start + 1), "{")
-            patch(tree.source, Span(tree.span.end - 1, tree.span.end), "}")
-      case _ => ()
+        Option.unless(tmpCtx.reporter.hasErrors)(name -> value)
+      case untpd.Parens(Assign(ident: untpd.Ident, value)) => Some(ident.name -> value)
+      case _ => None
+    }
+    assignmentArgs.foreach: (name, value) =>
+      // If there are no errors typing the above, then the named tuple is
+      // ambiguous and we issue a warning.
+      report.migrationWarning(DeprecatedAssignmentSyntax(name, value), tree.srcPos)
+      if MigrationVersion.AmbiguousNamedTupleSyntax.needsPatch then
+        patch(tree.source, Span(tree.span.start, tree.span.start + 1), "{")
+        patch(tree.source, Span(tree.span.end - 1, tree.span.end), "}")
 
   /** Retrieve symbol attached to given tree */
   protected def retrieveSym(tree: untpd.Tree)(using Context): Symbol = tree.removeAttachment(SymOfTree) match {
@@ -3621,6 +3624,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           case tree: untpd.SplicePattern => typedSplicePattern(tree, pt)
           case tree: untpd.MacroTree => report.error("Unexpected macro", tree.srcPos); tpd.nullLiteral  // ill-formed code may reach here
           case tree: untpd.Hole => typedHole(tree, pt)
+          case tree: untpd.Parens =>
+            checkDeprecatedAssignmentSyntax(tree)
+            typedUnadapted(desugar(tree, pt), pt, locked)
           case _ => typedUnadapted(desugar(tree, pt), pt, locked)
         }
 

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

@@ -79,6 +79,7 @@ class CompilationTests {
       compileFile("tests/rewrites/i20002.scala", defaultOptions.and("-indent", "-rewrite")),
       compileDir("tests/rewrites/annotation-named-pararamters", defaultOptions.and("-rewrite", "-source:3.6-migration")),
       compileFile("tests/rewrites/i21418.scala", unindentOptions.and("-rewrite", "-source:3.5-migration")),
+      compileFile("tests/rewrites/ambiguous-named-tuple-assignment.scala", defaultOptions.and("-rewrite", "-source:3.6-migration")),
       compileFile("tests/rewrites/i21382.scala", defaultOptions.and("-indent", "-rewrite")),
       compileFile("tests/rewrites/unused.scala", defaultOptions.and("-rewrite", "-Wunused:all")),
       compileFile("tests/rewrites/i22440.scala", defaultOptions.and("-rewrite"))

tests/rewrites/ambiguous-named-tuple-assignment.check

@@ -0,0 +1,17 @@
+object i21770:
+  def f(g: Int  => Unit) = g(0)
+  var cache: Option[Int] = None
+  f(i => {cache = Some(i)})
+
+object i21861:
+  var age: Int = 28
+  {
+    age = 29
+  }
+
+
+object i21861c:
+  def age: Int = ???
+  def age_=(x: Int): Unit = ()
+  age = 29
+  { age = 29 }

tests/rewrites/ambiguous-named-tuple-assignment.scala

@@ -0,0 +1,17 @@
+object i21770:
+  def f(g: Int  => Unit) = g(0)
+  var cache: Option[Int] = None
+  f(i => (cache = Some(i)))
+
+object i21861:
+  var age: Int = 28
+  (
+    age = 29
+  )
+
+
+object i21861c:
+  def age: Int = ???
+  def age_=(x: Int): Unit = ()
+  age = 29
+  ( age = 29 )

tests/warn/21681.check

@@ -1,7 +1,7 @@
 -- [E203] Syntax Migration Warning: tests/warn/21681.scala:3:2 ---------------------------------------------------------
 3 |  (age = 29) // warn
   |  ^^^^^^^^^^
-  |  Deprecated syntax: in the future it would be interpreted as a named tuple with one element,
+  |  Ambiguous syntax: this is interpreted as a named tuple with one element,
   |  not as an assignment.
   |
   |  To assign a value, use curly braces: `{age = 29}`.

tests/warn/21681b.check

@@ -1,7 +1,7 @@
 -- [E203] Syntax Migration Warning: tests/warn/21681b.scala:3:2 --------------------------------------------------------
 3 |  (age = 29) // warn
   |  ^^^^^^^^^^
-  |  Deprecated syntax: in the future it would be interpreted as a named tuple with one element,
+  |  Ambiguous syntax: this is interpreted as a named tuple with one element,
   |  not as an assignment.
   |
   |  To assign a value, use curly braces: `{age = 29}`.

tests/warn/21681c.check

@@ -1,7 +1,7 @@
 -- [E203] Syntax Migration Warning: tests/warn/21681c.scala:5:2 --------------------------------------------------------
 5 |  (age = 29) // warn
   |  ^^^^^^^^^^
-  |  Deprecated syntax: in the future it would be interpreted as a named tuple with one element,
+  |  Ambiguous syntax: this is interpreted as a named tuple with one element,
   |  not as an assignment.
   |
   |  To assign a value, use curly braces: `{age = 29}`.

tests/warn/21770.check

@@ -1,7 +1,7 @@
 -- [E203] Syntax Migration Warning: tests/warn/21770.scala:5:9 ---------------------------------------------------------
 5 |  f(i => (cache = Some(i))) // warn
   |         ^^^^^^^^^^^^^^^^^
-  |         Deprecated syntax: in the future it would be interpreted as a named tuple with one element,
+  |         Ambiguous syntax: this is interpreted as a named tuple with one element,
   |         not as an assignment.
   |
   |         To assign a value, use curly braces: `{cache = Some(i)}`.