Add migration rewrite deprecated assignment syntax

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

@@ -3350,6 +3350,7 @@ final class DeprecatedAssignmentSyntax(key: Name, value: untpd.Tree)(using Conte
       |not as an assignment.
       |
       |To assign a value, use curly braces: `{${key} = ${value}}`."""
+      + Message.rewriteNotice("This", version = SourceVersion.`3.6-migration`)
 
   override protected def explain(using Context): String = ""
 

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

@@ -3442,6 +3442,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           // 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 _ => ()
 
   /** Retrieve symbol attached to given tree */

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

@@ -80,6 +80,7 @@ class CompilationTests {
       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/infix-named-args.scala", defaultOptions.and("-rewrite", "-source:3.6-migration")),
+      compileFile("tests/rewrites/ambigious-named-tuple-assignment.scala", defaultOptions.and("-rewrite", "-source:3.6-migration")),
     ).checkRewrites()
   }
 

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

@@ -0,0 +1,19 @@
+import scala.language.experimental.namedTuples
+
+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/ambigious-named-tuple-assignment.scala

@@ -0,0 +1,19 @@
+import scala.language.experimental.namedTuples
+
+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

@@ -5,3 +5,4 @@
   |  not as an assignment.
   |
   |  To assign a value, use curly braces: `{age = 29}`.
+  |  This can be rewritten automatically under -rewrite -source 3.6-migration.

tests/warn/21681b.check

@@ -5,3 +5,4 @@
   |  not as an assignment.
   |
   |  To assign a value, use curly braces: `{age = 29}`.
+  |  This can be rewritten automatically under -rewrite -source 3.6-migration.

tests/warn/21681c.check

@@ -5,3 +5,4 @@
   |  not as an assignment.
   |
   |  To assign a value, use curly braces: `{age = 29}`.
+  |  This can be rewritten automatically under -rewrite -source 3.6-migration.

tests/warn/21770.check

@@ -5,3 +5,4 @@
   |         not as an assignment.
   |
   |         To assign a value, use curly braces: `{cache = Some(i)}`.
+  |         This can be rewritten automatically under -rewrite -source 3.6-migration.