Bring back pattern match exhaustivity checking for macros (#22622)

Fixes #22212

Author: jchyb

compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala

@@ -46,10 +46,8 @@ class PatternMatcher extends MiniPhase {
         case rt => tree.tpe
       val translated = new Translator(matchType, this).translateMatch(tree)
 
-      // Skip analysis on inlined code (eg pos/i19157)
-      if !tpd.enclosingInlineds.nonEmpty then
-        // check exhaustivity and unreachability
-        SpaceEngine.checkMatch(tree)
+      // check exhaustivity and unreachability
+      SpaceEngine.checkMatch(tree)
 
       translated.ensureConforms(matchType)
     }

compiler/src/dotty/tools/dotc/transform/patmat/Space.scala

@@ -917,6 +917,7 @@ object SpaceEngine {
     !sel.tpe.hasAnnotation(defn.UncheckedAnnot)
     && !sel.tpe.widen.isRef(defn.QuotedExprClass)
     && !sel.tpe.widen.isRef(defn.QuotedTypeClass)
+    && tpd.enclosingInlineds.isEmpty // Skip reachability on inlined code (eg i19157/i22212)
 
   def checkReachability(m: Match)(using Context): Unit = trace(i"checkReachability($m)"):
     val selTyp = toUnderlying(m.selector.tpe).dealias

tests/warn/i22212.check

@@ -0,0 +1,21 @@
+
+-- [E029] Pattern Match Exhaustivity Warning: tests/warn/i22212/Test_2.scala:3:19 --------------------------------------
+3 |    Macro.makeMatch() // warn: match may not be exhaustive.
+  |    ^^^^^^^^^^^^^^^^^
+  |    match may not be exhaustive.
+  |
+  |    It would fail on pattern case: Baz
+  |---------------------------------------------------------------------------------------------------------------------
+  |Inline stack trace
+  |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+  |This location contains code that was inlined from Macro_1.scala:7
+7 |      (_: Foo) match
+  |       ^^^^^^
+  |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+  |This location contains code that was inlined from Macro_1.scala:7
+7 |      (_: Foo) match
+  |      ^
+8 |        case Bar => ()
+   ---------------------------------------------------------------------------------------------------------------------
+  |
+  | longer explanation available when compiling with `-explain`

tests/warn/i22212/Data_1.scala

@@ -0,0 +1,3 @@
+sealed trait Foo
+case object Bar extends Foo
+case object Baz extends Foo

tests/warn/i22212/Macro_1.scala

@@ -0,0 +1,11 @@
+import scala.quoted._
+
+object Macro {
+  inline def makeMatch() = ${makeMatchImpl}
+  def makeMatchImpl(using Quotes) = {
+    '{
+      (_: Foo) match
+        case Bar => ()
+    }
+  }
+}

tests/warn/i22212/Test_2.scala

@@ -0,0 +1,3 @@
+object Test:
+  def main(args: Array[String]): Unit =
+    Macro.makeMatch() // warn: match may not be exhaustive.