Fix #6762: Add regression tests

tests/neg/i6762.check

@@ -0,0 +1,5 @@
+-- [E007] Type Mismatch Error: tests/neg/i6762.scala:5:72 --------------------------------------------------------------
+5 |def f(word: String)(given QuoteContext): Expr[Foo[G[String]]] = '{Foo(${word.toExpr})} // error
+  |                                                                        ^^^^
+  |                                                                        Found:    quoted.Expr[String]
+  |                                                                        Required: quoted.Expr[G[String]]

tests/neg/i6762.scala

@@ -0,0 +1,5 @@
+import scala.quoted.{_, given}
+
+type G[X]
+case class Foo[T](x: T)
+def f(word: String)(given QuoteContext): Expr[Foo[G[String]]] = '{Foo(${word.toExpr})} // error

tests/neg/i6762b.check

@@ -0,0 +1,5 @@
+-- [E007] Type Mismatch Error: tests/neg/i6762b.scala:4:39 -------------------------------------------------------------
+4 |def f(word: String): Expr[G[String]] = word.toExpr // error
+  |                                       ^^^^
+  |                                       Found:    Expr[String]
+  |                                       Required: Expr[G[String]]

tests/neg/i6762b.scala

@@ -0,0 +1,13 @@
+type Expr[T]
+type G[X]
+
+def f(word: String): Expr[G[String]] = word.toExpr // error
+
+def splice[T](e: Expr[T]): T = ???
+
+type Liftable
+given Liftable = ???
+
+implicit object ExprOps {
+  def (x: T) toExpr[T](given Liftable): Expr[T] = ???
+}