Bring back pattern match exhaustivity checking for macros

Also move the -Werror reporting until after the suspended warning
reporting - this was needed for the added test to work (as previously
the compilation would not error out even if -Werror was used).

Author: jchyb

compiler/src/dotty/tools/dotc/Run.scala

@@ -385,10 +385,10 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
     runPhases(allPhases = fusedPhases)(using runCtx)
     cancelAsyncTasty()
 
-    ctx.reporter.finalizeReporting()
     if (!ctx.reporter.hasErrors)
       Rewrites.writeBack()
     suppressions.runFinished(hasErrors = ctx.reporter.hasErrors)
+    ctx.reporter.finalizeReporting()
     while (finalizeActions.nonEmpty && canProgress()) {
       val action = finalizeActions.remove(0)
       action()

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

@@ -46,10 +46,13 @@ class PatternMatcher extends MiniPhase {
         case rt => tree.tpe
       val translated = new Translator(matchType, this).translateMatch(tree)
 
-      // Skip analysis on inlined code (eg pos/i19157)
+      // Skip unreachability analysis on inlined code (eg pos/i19157)
       if !tpd.enclosingInlineds.nonEmpty then
         // check exhaustivity and unreachability
         SpaceEngine.checkMatch(tree)
+      else
+        // only check exhaustivity
+        SpaceEngine.checkMatchExhaustivityOnly(tree)
 
       translated.ensureConforms(matchType)
     }

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

@@ -972,6 +972,10 @@ object SpaceEngine {
   end checkReachability
 
   def checkMatch(m: Match)(using Context): Unit =
-    if exhaustivityCheckable(m.selector) then checkExhaustivity(m)
+    checkMatchExhaustivityOnly(m)
     if reachabilityCheckable(m.selector) then checkReachability(m)
+
+  def checkMatchExhaustivityOnly(m: Match)(using Context): Unit =
+    if exhaustivityCheckable(m.selector) then checkExhaustivity(m)
+
 }

tests/neg-macros/i22212.check

@@ -0,0 +1,22 @@
+
+-- [E029] Pattern Match Exhaustivity Warning: tests/neg-macros/i22212/Test_2.scala:2:34 --------------------------------
+ 2 |@main def main() = Macro.makeMatch()
+   |                   ^^^^^^^^^^^^^^^^^
+   |                   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:11
+11 |      (_: Foo) match
+   |       ^^^^^^
+   |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   |This location contains code that was inlined from Macro_1.scala:11
+11 |      (_: Foo) match
+   |      ^
+12 |        case Bar => ()
+    --------------------------------------------------------------------------------------------------------------------
+   |
+   | longer explanation available when compiling with `-explain`
+No warnings can be incurred under -Werror (or -Xfatal-warnings)

tests/neg-macros/i22212/Macro_1.scala

@@ -0,0 +1,15 @@
+import scala.quoted._
+
+sealed trait Foo
+case object Bar extends Foo
+case object Baz extends Foo
+
+object Macro {
+  inline def makeMatch() = ${makeMatchImpl}
+  def makeMatchImpl(using Quotes) = {
+    '{
+      (_: Foo) match
+        case Bar => ()
+    }
+  }
+}

tests/neg-macros/i22212/Test_2.scala

@@ -0,0 +1,3 @@
+//> using options -Xfatal-warnings
+@main def main() = Macro.makeMatch()
+// nopos-error: No warnings can be incurred under -Werror (or -Xfatal-warnings)