diff --git a/compiler/test-resources/repl/i3536_bind b/compiler/test-resources/repl/i3536_bind
index 96ccdce81356..e1504cc5af3a 100644
--- a/compiler/test-resources/repl/i3536_bind
+++ b/compiler/test-resources/repl/i3536_bind
@@ -1,4 +1,4 @@
-scala> val res10 @ Some(_) = Option(1)
+scala> val res10 @ Some(_) = Option(1): @unchecked
 val res10: Some[Int] = Some(1)
 scala> res10
 val res11: Some[Int] = Some(1)
diff --git a/compiler/test-resources/repl/i3536_patterndef_some b/compiler/test-resources/repl/i3536_patterndef_some
index 24c8736b57b9..7492c16288e3 100644
--- a/compiler/test-resources/repl/i3536_patterndef_some
+++ b/compiler/test-resources/repl/i3536_patterndef_some
@@ -1,4 +1,4 @@
-scala> val Some((res40, res41)) = Option((1, 0))
+scala> val Some((res40, res41)) = Option((1, 0)): @unchecked
 val res40: Int = 1
 val res41: Int = 0
 scala> res40
diff --git a/compiler/test-resources/repl/i3966 b/compiler/test-resources/repl/i3966
index 9002c1607405..204a7685f854 100644
--- a/compiler/test-resources/repl/i3966
+++ b/compiler/test-resources/repl/i3966
@@ -1,2 +1,2 @@
-scala> val List(x: _*) = List(1, 2)
+scala> val List(x: _*) = List(1, 2): @unchecked
 val x: Seq[Int] = List(1, 2)
diff --git a/compiler/test-resources/repl/patdef b/compiler/test-resources/repl/patdef
index 12ba13bcd6d5..7bd06483934a 100644
--- a/compiler/test-resources/repl/patdef
+++ b/compiler/test-resources/repl/patdef
@@ -1,7 +1,7 @@
 scala> val Const, x = 0
 val Const: Int = 0
 val x: Int = 0
-scala> val (Const, List(`x`, _, a), b) = (0, List(0, 1337, 1), 2)
+scala> val (Const, List(`x`, _, a), b) = (0, List(0, 1337, 1), 2): @unchecked
 val a: Int = 1
 val b: Int = 2
 scala> val a@b = 0
diff --git a/compiler/test/dotty/tools/dotc/TastyBootstrapTests.scala b/compiler/test/dotty/tools/dotc/TastyBootstrapTests.scala
index 3164e11e9b2f..c95630144496 100644
--- a/compiler/test/dotty/tools/dotc/TastyBootstrapTests.scala
+++ b/compiler/test/dotty/tools/dotc/TastyBootstrapTests.scala
@@ -60,7 +60,7 @@ class TastyBootstrapTests {
       compileList("lib", librarySources,
         defaultOptions.and("-Ycheck-reentrant",
           "-language:experimental.erasedDefinitions", // support declaration of scala.compiletime.erasedValue
-          //  "-source", "future",  // TODO: re-enable once we allow : @unchecked in pattern definitions. Right now, lots of narrowing pattern definitions fail.
+          //  "-source", "future",  // TODO: re-enable once library uses updated syntax for vararg splices, wildcard imports, and import renaming
           ))(libGroup)
 
     val tastyCoreSources = sources(Paths.get("tasty/src"))
diff --git a/compiler/test/dotty/tools/dotc/ast/DesugarTests.scala b/compiler/test/dotty/tools/dotc/ast/DesugarTests.scala
index dc736596ed9b..43b71f191bd2 100644
--- a/compiler/test/dotty/tools/dotc/ast/DesugarTests.scala
+++ b/compiler/test/dotty/tools/dotc/ast/DesugarTests.scala
@@ -26,7 +26,7 @@ class DesugarTests extends DottyTest {
       val ccTree = tree.find(tree => tree.symbol.name == typeName("Foo")).get
       val List(_, foo) = defPath(ccTree.symbol, tree).map(_.symbol.info)
 
-      val x :: y :: rest = foo.decls.toList
+      val x :: y :: rest = foo.decls.toList: @unchecked
 
       // Make sure we extracted the correct values from foo:
       assert(x.name == termName("x"))
diff --git a/compiler/test/dotty/tools/dotc/printing/PrinterTests.scala b/compiler/test/dotty/tools/dotc/printing/PrinterTests.scala
index 23054cdf0dfb..64049453b595 100644
--- a/compiler/test/dotty/tools/dotc/printing/PrinterTests.scala
+++ b/compiler/test/dotty/tools/dotc/printing/PrinterTests.scala
@@ -47,7 +47,7 @@ class PrinterTests extends DottyTest {
 
     checkCompile("typer", source) { (tree, context) =>
       given Context = context
-      val bar @ Trees.DefDef(_, _, _, _) = tree.find(tree => tree.symbol.name == termName("bar2")).get
+      val bar @ Trees.DefDef(_, _, _, _) = tree.find(tree => tree.symbol.name == termName("bar2")).get: @unchecked
       assertEquals("Int & (Boolean | String)", bar.tpt.show)
     }
   }
diff --git a/compiler/test/dotty/tools/dotc/reporting/UserDefinedErrorMessages.scala b/compiler/test/dotty/tools/dotc/reporting/UserDefinedErrorMessages.scala
index bd72ac6c6288..4d73b0d88b55 100644
--- a/compiler/test/dotty/tools/dotc/reporting/UserDefinedErrorMessages.scala
+++ b/compiler/test/dotty/tools/dotc/reporting/UserDefinedErrorMessages.scala
@@ -26,7 +26,7 @@ class UserDefinedErrorMessages extends ErrorMessagesTest {
       given Context = itcx
 
       assertMessageCount(1, messages)
-      val (m: NoExplanation) :: Nil = messages
+      val (m: NoExplanation) :: Nil = messages: @unchecked
 
       assertEquals(m.msg, "Could not prove Int =!= Int")
     }
@@ -50,7 +50,7 @@ class UserDefinedErrorMessages extends ErrorMessagesTest {
       given Context = itcx
 
       assertMessageCount(1, messages)
-      val (m: NoExplanation) :: Nil = messages
+      val (m: NoExplanation) :: Nil = messages: @unchecked
 
       assertEquals(m.msg, "Could not prove Int =!= Int")
     }
@@ -75,7 +75,7 @@ class UserDefinedErrorMessages extends ErrorMessagesTest {
       given Context = itcx
 
       assertMessageCount(1, messages)
-      val (m: NoExplanation) :: Nil = messages
+      val (m: NoExplanation) :: Nil = messages: @unchecked
 
       assertEquals(m.msg, "Could not prove Int =!= Int")
     }
@@ -97,7 +97,7 @@ class UserDefinedErrorMessages extends ErrorMessagesTest {
       given Context = itcx
 
       assertMessageCount(1, messages)
-      val (m: NoExplanation) :: Nil = messages
+      val (m: NoExplanation) :: Nil = messages: @unchecked
 
       assertEquals(m.msg, "msg A=Any")
     }
@@ -119,7 +119,7 @@ class UserDefinedErrorMessages extends ErrorMessagesTest {
       given Context = itcx
 
       assertMessageCount(1, messages)
-      val (m: NoExplanation) :: Nil = messages
+      val (m: NoExplanation) :: Nil = messages: @unchecked
 
       assertEquals(m.msg, "msg A=Any")
     }
diff --git a/compiler/test/dotty/tools/repl/ReplCompilerTests.scala b/compiler/test/dotty/tools/repl/ReplCompilerTests.scala
index 963f269af8a6..866647476888 100644
--- a/compiler/test/dotty/tools/repl/ReplCompilerTests.scala
+++ b/compiler/test/dotty/tools/repl/ReplCompilerTests.scala
@@ -213,18 +213,18 @@ class ReplCompilerTests extends ReplTest:
   }
 
   @Test def `i10214 must show classic MatchError` = initially {
-    run("val 1 = 2")
+    run("val 1 = 2: @unchecked")
     assertEquals("scala.MatchError: 2 (of class java.lang.Integer)", storedOutput().linesIterator.next())
   }
   @Test def `i10214 must show useful regex MatchError` =
     initially {
       run("""val r = raw"\d+".r""")
     } andThen {
-      run("""val r() = "abc"""")
+      run("""val r() = "abc": @unchecked""")
       assertEquals("scala.MatchError: abc (of class java.lang.String)", storedOutput().linesIterator.drop(1).next())
     }
   @Test def `i10214 must show MatchError on literal type` = initially {
-    run("val (x: 1) = 2")
+    run("val (x: 1) = 2: @unchecked")
     assertEquals("scala.MatchError: 2 (of class java.lang.Integer)", storedOutput().linesIterator.next())
   }
   @Test def `i12920 must truncate stack trace to user code` = initially {
@@ -328,7 +328,7 @@ class ReplCompilerTests extends ReplTest:
   }
 
   @Test def i14473 = initially {
-    run("""val (x,y) = if true then "hi" else (42,17)""")
+    run("""val (x,y) = (if true then "hi" else (42,17)): @unchecked""")
     val all = lines()
     assertEquals(2, all.length)
     assertEquals("scala.MatchError: hi (of class java.lang.String)", all.head)
diff --git a/scaladoc/test/dotty/tools/scaladoc/tasty/comments/MemberLookupTests.scala b/scaladoc/test/dotty/tools/scaladoc/tasty/comments/MemberLookupTests.scala
index 0b9b88fa5bb8..c246401c75fc 100644
--- a/scaladoc/test/dotty/tools/scaladoc/tasty/comments/MemberLookupTests.scala
+++ b/scaladoc/test/dotty/tools/scaladoc/tasty/comments/MemberLookupTests.scala
@@ -60,7 +60,7 @@ class LookupTestCases[Q <: Quotes](val q: Quotes) {
     val target = wrappedTarget.symbol
     val lookupRes = MemberLookup.lookupOpt(parseQuery(query), None)
     assertTrue(s"Couldn't look up: $query", lookupRes.nonEmpty)
-    val Some((lookedUp, _, _)) = lookupRes
+    val Some((lookedUp, _, _)) = lookupRes: @unchecked
     assertSame(query, target, lookedUp)
   }
 
@@ -83,7 +83,7 @@ class LookupTestCases[Q <: Quotes](val q: Quotes) {
       val target = sym.symbol
       val lookupRes = MemberLookup.lookupOpt(parseQuery(query), None)
       assertTrue(s"Couldn't look up: $query", lookupRes.nonEmpty)
-      val Some((_ , _, Some(owner))) = lookupRes
+      val Some((_ , _, Some(owner))) = lookupRes: @unchecked
       assertSame(query, target, owner)
     }
   }
@@ -102,7 +102,7 @@ class LookupTestCases[Q <: Quotes](val q: Quotes) {
       val lookupRes = MemberLookup.lookupOpt(parseQuery(query), Some(cls("scala.=:=").symbol))
       assertTrue(s"Couldn't look up: $query", lookupRes.nonEmpty)
       println(lookupRes)
-      val Some((_ , _, owner)) = lookupRes
+      val Some((_ , _, owner)) = lookupRes: @unchecked
       assertSame(query, None, owner)
     }
   }
@@ -161,7 +161,7 @@ class LookupTestCases[Q <: Quotes](val q: Quotes) {
     )
 
     cases.foreach { case ((Sym(owner), query), Sym(target)) =>
-      val Some((lookedUp, _, _)) = MemberLookup.lookup(parseQuery(query), owner)
+      val Some((lookedUp, _, _)) = MemberLookup.lookup(parseQuery(query), owner): @unchecked
       assertSame(s"$owner / $query", target, lookedUp)
     }
   }
@@ -176,7 +176,7 @@ class LookupTestCases[Q <: Quotes](val q: Quotes) {
   given q.type = q
 
   def parseQuery(query: String): Query = {
-    val Right(parsed) = QueryParser(query).tryReadQuery()
+    val Right(parsed) = QueryParser(query).tryReadQuery(): @unchecked
     parsed
   }
 
diff --git a/scaladoc/test/dotty/tools/scaladoc/tasty/comments/QueryParserTests.scala b/scaladoc/test/dotty/tools/scaladoc/tasty/comments/QueryParserTests.scala
index 676a11348a5f..0d33a9363bac 100644
--- a/scaladoc/test/dotty/tools/scaladoc/tasty/comments/QueryParserTests.scala
+++ b/scaladoc/test/dotty/tools/scaladoc/tasty/comments/QueryParserTests.scala
@@ -64,12 +64,12 @@ class QueryParserTests {
   private def parse(input: String) = QueryParser(input).tryReadQuery()
 
   private def testSuccess(input: String, expected: Query) = {
-    val Right(got) = parse(input)
+    val Right(got) = parse(input): @unchecked
     assertEquals(expected, got)
   }
 
   private def testFailAt(input: String, char: Int) = {
-    val Left(err) = parse(input)
+    val Left(err) = parse(input): @unchecked
     assertEquals(s"expected to fail at $char : $input", char, err.at)
   }
 }
diff --git a/tests/neg-macros/i6432/Macro_1.scala b/tests/neg-macros/i6432/Macro_1.scala
index e2628fd45f7f..992cdc62ceaf 100644
--- a/tests/neg-macros/i6432/Macro_1.scala
+++ b/tests/neg-macros/i6432/Macro_1.scala
@@ -9,7 +9,7 @@ object Macro {
     import quotes.reflect.*
     sc match {
       case '{ StringContext(${Varargs(parts)}*) } =>
-        for (part @ Expr(s) <- parts)
+        for (case part @ Expr(s) <- parts)
           report.error(s, part.asTerm.pos)
     }
     '{}
diff --git a/tests/neg-macros/i6432b/Macro_1.scala b/tests/neg-macros/i6432b/Macro_1.scala
index e2628fd45f7f..992cdc62ceaf 100644
--- a/tests/neg-macros/i6432b/Macro_1.scala
+++ b/tests/neg-macros/i6432b/Macro_1.scala
@@ -9,7 +9,7 @@ object Macro {
     import quotes.reflect.*
     sc match {
       case '{ StringContext(${Varargs(parts)}*) } =>
-        for (part @ Expr(s) <- parts)
+        for (case part @ Expr(s) <- parts)
           report.error(s, part.asTerm.pos)
     }
     '{}
diff --git a/tests/neg/t5702-neg-bad-and-wild.check b/tests/neg/t5702-neg-bad-and-wild.check
index 623bf3002cca..f6d761a6726f 100644
--- a/tests/neg/t5702-neg-bad-and-wild.check
+++ b/tests/neg/t5702-neg-bad-and-wild.check
@@ -56,3 +56,19 @@
    |                   Recursive value $1$ needs type
    |
    | longer explanation available when compiling with `-explain`
+-- Warning: tests/neg/t5702-neg-bad-and-wild.scala:22:20 ---------------------------------------------------------------
+22 |    val K(x @ _*) = k
+   |                    ^
+   |        pattern's type Int* does not match the right hand side expression's type Int
+   |
+   |        If the narrowing is intentional, this can be communicated by adding `: @unchecked` after the expression,
+   |        which may result in a MatchError at runtime.
+   |        This patch can be rewritten automatically under -rewrite -source 3.2-migration.
+-- Warning: tests/neg/t5702-neg-bad-and-wild.scala:25:20 ---------------------------------------------------------------
+25 |    val (b, _ * ) = (5,6) // ok
+   |                    ^^^^^
+   |        pattern's type Int* does not match the right hand side expression's type Int
+   |
+   |        If the narrowing is intentional, this can be communicated by adding `: @unchecked` after the expression,
+   |        which may result in a MatchError at runtime.
+   |        This patch can be rewritten automatically under -rewrite -source 3.2-migration.
diff --git a/tests/patmat/for.scala b/tests/patmat/for.scala
index 4c2ed262fc30..14e5de351212 100644
--- a/tests/patmat/for.scala
+++ b/tests/patmat/for.scala
@@ -3,5 +3,5 @@ object Test {
     for ((a, b) <- l) yield a
   }
 
-  def bar(xs: List[(Int, List[Int])]): Unit = for ( (_, x :: y :: xs) <- xs) yield x
+  def bar(xs: List[(Int, List[Int])]): Unit = for (case (_, x :: y :: xs) <- xs) yield x
 }
\ No newline at end of file
diff --git a/tests/pos-special/fatal-warnings/i6621.scala b/tests/pos-special/fatal-warnings/i6621.scala
index a006c1254ae0..92362a004530 100644
--- a/tests/pos-special/fatal-warnings/i6621.scala
+++ b/tests/pos-special/fatal-warnings/i6621.scala
@@ -4,5 +4,5 @@ object Unapply {
 }
 
 object Test {
-  val Unapply(x, y) = ""
+  val Unapply(x, y) = "": @unchecked
 }
diff --git a/tests/pos/i14587.hard-union-tuples.scala b/tests/pos/i14587.hard-union-tuples.scala
index 2d4ebcf93cc0..e1a086655e5f 100644
--- a/tests/pos/i14587.hard-union-tuples.scala
+++ b/tests/pos/i14587.hard-union-tuples.scala
@@ -3,8 +3,9 @@ class Test:
   type Foo = Option[String] | Option[Int]
 
   def test(foo: Foo) =
-    val (_, foo2: Foo) = // was: the type test for Test.this.Foo cannot be checked at runtime
+    val (_, foo2: Foo) = ( // was: the type test for Test.this.Foo cannot be checked at runtime
       foo match
         case Some(s: String) => ((), s)
         case _               => ((), 0)
+    ): @unchecked
     foo2
diff --git a/tests/semanticdb/expect/Synthetic.expect.scala b/tests/semanticdb/expect/Synthetic.expect.scala
index 2672b8106785..a4419aa8bd82 100644
--- a/tests/semanticdb/expect/Synthetic.expect.scala
+++ b/tests/semanticdb/expect/Synthetic.expect.scala
@@ -9,11 +9,11 @@ class Synthetic/*<-example::Synthetic#*/ {
 
   // See https://github.com/scalameta/scalameta/issues/977
   val Name/*<-example::Synthetic#Name.*/ = "name:(.*)".r/*->scala::collection::StringOps#r().*/
-  val x/*<-example::Synthetic#x.*/ #::/*->scala::package.`#::`.*/ xs/*<-example::Synthetic#xs.*/ = LazyList/*->scala::package.LazyList.*/(1, 2)
-  val Name/*->example::Synthetic#Name.*/(name/*<-example::Synthetic#name.*/) = "name:foo"
+  val x/*<-example::Synthetic#x.*/ #::/*->scala::package.`#::`.*/ xs/*<-example::Synthetic#xs.*/ = LazyList/*->scala::package.LazyList.*/(1, 2): @unchecked
+  val Name/*->example::Synthetic#Name.*/(name/*<-example::Synthetic#name.*/) = "name:foo": @unchecked
   1 #:: 2 #:: LazyList/*->scala::package.LazyList.*/.empty/*->scala::collection::immutable::LazyList.empty().*/
 
-  val a1/*<-example::Synthetic#a1.*/ #::/*->scala::package.`#::`.*/ a2/*<-example::Synthetic#a2.*/ #::/*->scala::package.`#::`.*/ as/*<-example::Synthetic#as.*/ = LazyList/*->scala::package.LazyList.*/(1, 2)
+  val a1/*<-example::Synthetic#a1.*/ #::/*->scala::package.`#::`.*/ a2/*<-example::Synthetic#a2.*/ #::/*->scala::package.`#::`.*/ as/*<-example::Synthetic#as.*/ = LazyList/*->scala::package.LazyList.*/(1, 2): @unchecked
 
   val lst/*<-example::Synthetic#lst.*/ = 1 #:: 2 #:: LazyList/*->scala::package.LazyList.*/.empty/*->scala::collection::immutable::LazyList.empty().*/
 
diff --git a/tests/semanticdb/expect/Synthetic.scala b/tests/semanticdb/expect/Synthetic.scala
index 10d13e936468..71fb5fdf70a3 100644
--- a/tests/semanticdb/expect/Synthetic.scala
+++ b/tests/semanticdb/expect/Synthetic.scala
@@ -9,11 +9,11 @@ class Synthetic {
 
   // See https://github.com/scalameta/scalameta/issues/977
   val Name = "name:(.*)".r
-  val x #:: xs = LazyList(1, 2)
-  val Name(name) = "name:foo"
+  val x #:: xs = LazyList(1, 2): @unchecked
+  val Name(name) = "name:foo": @unchecked
   1 #:: 2 #:: LazyList.empty
 
-  val a1 #:: a2 #:: as = LazyList(1, 2)
+  val a1 #:: a2 #:: as = LazyList(1, 2): @unchecked
 
   val lst = 1 #:: 2 #:: LazyList.empty