Add spec for quoted patterns

Author: nicolasstucki

docs/docs/reference/other-new-features/quoted-pattern-spec.md

@@ -0,0 +1,77 @@
+---
+layout: doc-page
+title: "Pattern Matching on Quoted Code"
+---
+
+
+
+## Overview
+
+```scala
+def foo(x: Expr[Int]) given tasty.Reflect: Expr[Int] = x match {
+  case '{ val $a = $x; (${Bind(`a`)}: Int) + ($y: Int) } => '{ $x + $y } // TODO needs fix for #6328, `a` is currently not in scope while typing
+}
+```
+
+```scala
+def foo(x: Expr[Int]) given tasty.Reflect: Expr[Int] = x match {
+  case scala.internal.quoted.Matcher.unapply[Tuple3[Bind[Int], Expr[Int], Expr[Int]]](Tuple3(a, x, Bind(`a`), y))('{ @patternBindHole val a: Int = patternHole[Int]; patternHole[Int] + patternHole[Int] }) => 
+}
+```
+
+
+## Matcher
+
+At runtime to a `quoted.Expr` can be matched to another using `scala.internal.quoted.Matcher.unapply`.
+
+```scala
+def unapply[Tup <: Tuple](scrutineeExpr: Expr[_])(implicit patternExpr: Expr[_], reflection: Reflection): Option[Tup]
+```
+
+The `scrutineeExpr` is a normal quoted expression while `patternExpr` may contain holes representing splices. 
+The result of pattern matching is `None` if the expressions are not equivalent, otherwise it returns `Some` (some tuple) containing the contents of the matched holes.
+
+
+| Expression                | Pattern                  |                                                                            |
+| :-----------------------: |:-----------------------: | -------------------------------------------------------------------------: |
+| Literal `a`               | Literal `x`              | matches if `a == x`                                                        |
+| `a`                       | `x`                      | matches if `a` and `x` refer to the same symbol                            |
+| `a.b`                     | `x.y`                    | matches if `b` and `y` refer to the same symbol and `a` matches `x`        |
+| `a: A`                    | `x: X`                   | matches if `a` matches `x` and `A` matches `X`                             |
+| `fa(.. bi ..)`            | `fx(.. xi ..)`           | matches if `fa` matches `fx` and for all `i` `ai` matches `xi`             |
+| `fa[.. Ai ..]`            | `fx[.. Xi ..]`           | matches if `fa` matches `fx` and for all `i` `Ai` matches `Xi`             |
+| `{.. ai ..}`              | `{.. xi ..}`             | matches if all `i` `ai` matches `xi`                                       |
+| `if (a) b else c`         | `if (x) y else z`        | matches if `a` matches `x`, `b` matches `y` and `c` matches `z`            |
+| `while (a) b`             | `while (x) y`            | matches if `a` matches `x` and `b` matches `y`                             |
+| Assignment `a = b`        | Assignment `x = y`       | matches if `a` matches `x`, `b` matches `y`                                |
+| Named argument `n = a`    | Named argument `m = x    | matches if `c1` matches `c2`, `t1` matches `t2` and `e1` matches `e2`      |
+| `new A`                   | `new X`                  | matches if `A` matches `B`                                                 |
+| `this`                    | `this`                   | matches if both refer to the same symbol                                   |
+| `a.super[B]`              | `x.super[Y]`             | matches if `a` matches `x` and `A` equals `Y`                              |
+| Repeated `ai`             | Repeated `xi`            | matches if for all `i` `ai` matches `xi`                                   |
+> ValDef
+> DefDef
+> Lambda
+> Match
+> Try
+
+| Type                      | Pattern                  |                                                                            |
+| :-----------------------: |:-----------------------: | -------------------------------------------------------------------------: |
+| Inferred `A`              | Inferred `X`             | matches if `A <:< B`                                                       |
+> Applied Type
+> Annotated
+
+
+| Pattern inside the quote    | Pattern                     |                                                                                    |
+| :-------------------------: |:--------------------------: | ---------------------------------------------------------------------------------: |
+| Value `a`                   | Value `x`                   | matches if `a` matches `x`                                                         |
+| `a: A`                      | `x: X`                      | matches if `A` matches `X`                                                         |
+| `a @ b`                     | `x @ y`                     | makes symbols of `a` and `x` equivalent and matches if `b` matches `y`             |
+| Unapply `a(..bi..)(..ci..)` | Unapply `x(..yi..)(..zi..)` | matches if `a` matches `x` and for all `i` `bi` matches `yi` and `ci` matches `zi` |
+| `.. | ai | ..`              | `.. | xi | ..`              | matches if for all `i` `ai` matches `xi`                                           |
+| `_`                         | `_`                         | always matches                                                                     |
+
+
+## Quoted Patterns
+
+