Space: Replace showType & make Space Showable

Replace showType with a small tweak to RefinedPrinter, so the rest of
the logic is followed.  For instance, show infix types and tuples
correctly.

Also, make Space Showable, reusing the existing logic for Space, but
additionally specifying the Space class name, which is important for
following Space traces.

compiler/test/dotty/tools/dotc/transform/patmat/SpaceEngineTest.scala

@@ -27,12 +27,12 @@ class SpaceEngineTest:
     val a = Prod(tp, unappTp, params)
     val b = Empty
 
-    val res1 = isSubspace(a, b)
+    val res1 = a.isSubspace(b)
 
-    val a2   = simplify(a)
-    val b2   = simplify(b)
+    val a2   = a.simplify
+    val b2   = b.simplify
     val rem1 = minus(a2, b2)
-    val rem2 = simplify(rem1)
+    val rem2 = rem1.simplify
     val res2 = rem2 == Empty
 
     assertEquals(
@@ -46,19 +46,12 @@ class SpaceEngineTest:
           |simplify(rem1)                      == Empty
           |rem2                                == Empty
           |
-          |a    = ${show(a)}
-          |b    = ${show(b)}
-          |a2   = ${show(a2)}
-          |b2   = ${show(b2)}
-          |rem1 = ${show(rem1)}
-          |rem2 = ${show(rem2)}
-          |
-          |a    = ${a.toString}
-          |b    = ${b.toString}
-          |a2   = ${a2.toString}
-          |b2   = ${b2.toString}
-          |rem1 = ${rem1.toString}
-          |rem2 = ${rem2.toString}
+          |a    = $a
+          |b    = $b
+          |a2   = $a2
+          |b2   = $b2
+          |rem1 = $rem1
+          |rem2 = $rem2
           |
           |""".stripMargin, res1, res2)
   }

tests/patmat/aliasing.check

@@ -1,3 +1,3 @@
-14: Pattern Match Exhaustivity: _: Trait & Test.Alias1, _: Clazz & Test.Alias1
-19: Pattern Match Exhaustivity: _: Trait & Test.Alias2
-23: Pattern Match Exhaustivity: _: Trait & (Test.Alias2 & OpenTrait2){val x: Int}
+14: Pattern Match Exhaustivity: _: Trait & Alias1, _: Clazz & Alias1
+19: Pattern Match Exhaustivity: _: Trait & Alias2
+23: Pattern Match Exhaustivity: _: Trait & (Alias2 & OpenTrait2){val x: Int}

tests/patmat/i12020.check

@@ -1 +1 @@
-19: Pattern Match Exhaustivity: _: TypeDef
+19: Pattern Match Exhaustivity: _: x$1.reflect.TypeDef

tests/patmat/i2502.check

@@ -1 +1 @@
-5: Pattern Match Exhaustivity: _: BTypes.ClassBType
+5: Pattern Match Exhaustivity: _: BTypes.this.ClassBType

tests/patmat/i2502b.check

@@ -1 +1 @@
-5: Pattern Match Exhaustivity: _: BTypes.ClassBType
+5: Pattern Match Exhaustivity: _: BTypes.this.ClassBType

tests/patmat/i3938.check

@@ -1 +1 @@
-34: Pattern Match Exhaustivity: bar.C()
+34: Pattern Match Exhaustivity: foo.bar.C()

tests/patmat/i6255b.check

@@ -1 +1 @@
-3: Pattern Match Exhaustivity: _: Expr[Int]
+3: Pattern Match Exhaustivity: _: scala.quoted.Expr[Int]

tests/patmat/t10100.check

@@ -1 +1 @@
-12: Pattern Match Exhaustivity: (_, FancyFoo(_))
+12: Pattern Match Exhaustivity: (_, NonExhaustive#FancyFoo(_))

tests/patmat/t9779.check

@@ -1 +1 @@
-10: Pattern Match Exhaustivity: _: a.Elem[_]
+10: Pattern Match Exhaustivity: _: a.Elem[?]