Defer the pattern matching phase until after refchecks

Continuing from scala#6552.

The motivation is run the pickler phase earlier, as its intermediate
output can be used as an input to downstream compilation in a
pipelined build architecture.

(cherry picked from commit 8fd8e36)

Author: retronym

src/compiler/scala/tools/nsc/Global.scala

@@ -487,15 +487,6 @@ class Global(var currentSettings: Settings, reporter0: Reporter)
     val global: Global.this.type = Global.this
   } with Analyzer
 
-  // phaseName = "patmat"
-  object patmat extends {
-    val global: Global.this.type = Global.this
-    val runsAfter = List("typer")
-    val runsRightAfter = None
-    // patmat doesn't need to be right after typer, as long as we run before superaccessors
-    // (sbt does need to run right after typer, so don't conflict)
-  } with PatternMatching
-
   // phaseName = "superaccessors"
   object superAccessors extends {
     val global: Global.this.type = Global.this
@@ -524,10 +515,20 @@ class Global(var currentSettings: Settings, reporter0: Reporter)
     val runsRightAfter = None
   } with RefChecks
 
+  // phaseName = "patmat"
+  object patmat extends {
+    val global: Global.this.type = Global.this
+    // patmat does not need to run before the superaccessors phase, because
+    // patmat never emits `this.x` where `x` is a ParamAccessor.
+    // (However, patmat does need to run before outer accessors generation).
+    val runsAfter = List("refchecks")
+    val runsRightAfter = None
+  } with PatternMatching
+
   // phaseName = "uncurry"
   override object uncurry extends {
     val global: Global.this.type = Global.this
-    val runsAfter = List("refchecks")
+    val runsAfter = List("patmat")
     val runsRightAfter = None
   } with UnCurry
 

test/files/neg/t6446-additional.check

@@ -4,11 +4,11 @@
          namer   2  resolve names, attach symbols to named trees
 packageobjects   3  load package objects
          typer   4  the meat and potatoes: type the trees
-        patmat   5  translate match expressions
-superaccessors   6  add super accessors in traits and nested classes
-    extmethods   7  add extension methods for inline classes
-       pickler   8  serialize symbol tables
-     refchecks   9  reference/override checking, translate nested objects
+superaccessors   5  add super accessors in traits and nested classes
+    extmethods   6  add extension methods for inline classes
+       pickler   7  serialize symbol tables
+     refchecks   8  reference/override checking, translate nested objects
+        patmat   9  translate match expressions
        uncurry  10  uncurry, translate function values to anonymous classes
         fields  11  synthesize accessors and fields, add bitmaps for lazy vals
      tailcalls  12  replace tail calls by jumps

test/files/neg/t6446-missing.check

@@ -5,11 +5,11 @@ Error: unable to load class: t6446.Ploogin
          namer   2  resolve names, attach symbols to named trees
 packageobjects   3  load package objects
          typer   4  the meat and potatoes: type the trees
-        patmat   5  translate match expressions
-superaccessors   6  add super accessors in traits and nested classes
-    extmethods   7  add extension methods for inline classes
-       pickler   8  serialize symbol tables
-     refchecks   9  reference/override checking, translate nested objects
+superaccessors   5  add super accessors in traits and nested classes
+    extmethods   6  add extension methods for inline classes
+       pickler   7  serialize symbol tables
+     refchecks   8  reference/override checking, translate nested objects
+        patmat   9  translate match expressions
        uncurry  10  uncurry, translate function values to anonymous classes
         fields  11  synthesize accessors and fields, add bitmaps for lazy vals
      tailcalls  12  replace tail calls by jumps

test/files/neg/t6446-show-phases.check

@@ -4,11 +4,11 @@
          namer   2  resolve names, attach symbols to named trees
 packageobjects   3  load package objects
          typer   4  the meat and potatoes: type the trees
-        patmat   5  translate match expressions
-superaccessors   6  add super accessors in traits and nested classes
-    extmethods   7  add extension methods for inline classes
-       pickler   8  serialize symbol tables
-     refchecks   9  reference/override checking, translate nested objects
+superaccessors   5  add super accessors in traits and nested classes
+    extmethods   6  add extension methods for inline classes
+       pickler   7  serialize symbol tables
+     refchecks   8  reference/override checking, translate nested objects
+        patmat   9  translate match expressions
        uncurry  10  uncurry, translate function values to anonymous classes
         fields  11  synthesize accessors and fields, add bitmaps for lazy vals
      tailcalls  12  replace tail calls by jumps

test/files/neg/t7494-no-options.check

@@ -5,11 +5,11 @@ error: Error: ploogin takes no options
          namer   2  resolve names, attach symbols to named trees
 packageobjects   3  load package objects
          typer   4  the meat and potatoes: type the trees
-        patmat   5  translate match expressions
-superaccessors   6  add super accessors in traits and nested classes
-    extmethods   7  add extension methods for inline classes
-       pickler   8  serialize symbol tables
-     refchecks   9  reference/override checking, translate nested objects
+superaccessors   5  add super accessors in traits and nested classes
+    extmethods   6  add extension methods for inline classes
+       pickler   7  serialize symbol tables
+     refchecks   8  reference/override checking, translate nested objects
+        patmat   9  translate match expressions
        uncurry  10  uncurry, translate function values to anonymous classes
         fields  11  synthesize accessors and fields, add bitmaps for lazy vals
      tailcalls  12  replace tail calls by jumps

test/files/run/programmatic-main.check

@@ -4,11 +4,11 @@
          namer   2  resolve names, attach symbols to named trees
 packageobjects   3  load package objects
          typer   4  the meat and potatoes: type the trees
-        patmat   5  translate match expressions
-superaccessors   6  add super accessors in traits and nested classes
-    extmethods   7  add extension methods for inline classes
-       pickler   8  serialize symbol tables
-     refchecks   9  reference/override checking, translate nested objects
+superaccessors   5  add super accessors in traits and nested classes
+    extmethods   6  add extension methods for inline classes
+       pickler   7  serialize symbol tables
+     refchecks   8  reference/override checking, translate nested objects
+        patmat   9  translate match expressions
        uncurry  10  uncurry, translate function values to anonymous classes
         fields  11  synthesize accessors and fields, add bitmaps for lazy vals
      tailcalls  12  replace tail calls by jumps

test/files/run/t1434.check

@@ -0,0 +1,3 @@
+t1434.scala:7: warning: comparing values of types Null and Null using `!=' will always yield false
+    case a: A[_] if(a.op != null) => "with op"
+                         ^

test/files/run/t6288.check

@@ -5,7 +5,7 @@
       [106][106][106]Case3.super.<init>();
       [13]()
     };
-    [21]def unapply([29]z: [32]<type: [32]scala.Any>): [21]Option[Int] = [56][52][52]scala.Some.apply[[52]Int]([57]-1);
+    [21]def unapply([29]z: [32]<type: [32]scala.Any>): [21]Option[Int] = [56][52][52]new [52]Some[Int]([57]-1);
     [64]{
       [64]case <synthetic> val x1: [64]String = [64]"";
       [64]case5()[84]{