Add typeChecks to the library

Follow up of #6135

Author: nicolasstucki

library/src-bootstrapped/scala/tests/TypeChecking.scala

@@ -0,0 +1,15 @@
+package scala.tests
+
+import scala.quoted._
+import scala.tasty.Reflection
+
+object TypeChecking {
+
+  inline def typeChecks(inline code: String): Boolean = ${ typeChecksImpl(code) }
+
+  private def typeChecksImpl(code: String)(implicit reflect: Reflection): Expr[Boolean] = {
+    import reflect._
+    typing.typeChecks(code).toExpr
+  }
+
+}

tests/run-with-compiler/scala-tests-typeChecks.scala

@@ -0,0 +1,41 @@
+import scala.tests.TypeChecking._
+
+object Test {
+
+  trait Eq[T]
+  implicit val eq: Eq[Int] = new Eq[Int] {}
+
+  implicit class AnyOps[T](x: T) {
+    def === (y: T)(implicit c: Eq[T]) = x == y
+  }
+
+  def main(args: Array[String]): Unit = {
+    assert(typeChecks("5 === 5"))
+    assert(!typeChecks("5.6 === 7.7"))
+
+    val x: Int = 5
+    assert(typeChecks("x + 3"))
+    assert(!typeChecks("y + 3"))
+    import scala.util.Left
+    assert(typeChecks("Left(3)"))
+    assert(!typeChecks("Rigth(3)"))
+
+    def f(x: Int): Int = x * x
+    assert(typeChecks("f(3)"))
+    assert(!typeChecks("g(3)"))
+
+    type T
+    assert(typeChecks("def foo(x: T): T = x"))
+    assert(!typeChecks("foo(???)"))
+    assert(!typeChecks("def foo(x: S): S = x"))
+
+    assert(!typeChecks("def test(x: Int) ="))
+
+    assert(typeChecks(
+      """
+      class EqString extends Eq[String]
+      new EqString
+      """
+    ))
+  }
+}