Coverage: mark case bodies as branches; don't ignore branches with sy…

…nthetic spans (scala#18437)

Marking bodies of CaseDefs as branches seems like an uncontroversial
change, it was probably an oversight.

Not ignoring synthetic spans when creating coverage calls in branches
seems like a good trade off. There might be some auto-generated `else
()` interpreted as branches, but Scala introduces quite a lot of
synthetic trees that wrap non-synthetic trees (e.g. implicit classes).
Also, it looks like Scala 2 includes those compiler-generated `else`
branches in coverage. (Another possibility here would be to also check
if the span is zero extent, but that approach would be different to the
Scala 2 one)

partial fix for scala#16634

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

@@ -188,12 +188,9 @@ class InstrumentCoverage extends MacroTransform with IdentityDenotTransformer:
      * If the tree is empty, return itself and don't instrument.
      */
     private def transformBranch(tree: Tree)(using Context): Tree =
-      import dotty.tools.dotc.core.Decorators.{show,i}
-      if tree.isEmpty || tree.span.isSynthetic then
+      if tree.isEmpty then
         // - If t.isEmpty then `transform(t) == t` always hold,
         //   so we can avoid calling transform in that case.
-        // - If tree.span.isSynthetic then the branch has been generated
-        //   by the frontend phases, so we don't want to instrument it.
         tree
       else
         val transformed = transform(tree)
@@ -353,10 +350,8 @@ class InstrumentCoverage extends MacroTransform with IdentityDenotTransformer:
       // recursively transform the guard, but keep the pat
       val transformedGuard = transform(guard)
 
-      // ensure that the body is always instrumented by inserting a call to Invoker.invoked at its beginning
-      val coverageCall = createInvokeCall(tree.body, pos)
-      val transformedBody = transform(tree.body)
-      val instrumentedBody = InstrumentedParts.singleExprTree(coverageCall, transformedBody)
+      // ensure that the body is always instrumented as a branch
+      val instrumentedBody = transformBranch(tree.body)
 
       cpy.CaseDef(tree)(pat, transformedGuard, instrumentedBody)
 

tests/coverage/pos/Inlined.scoverage.check

@@ -59,6 +59,23 @@ Inlined$package$
 Object
 covtest.Inlined$package$
 testInlined
+330
+330
+10
+<none>
+Literal
+true
+0
+false
+
+
+3
+Inlined.scala
+covtest
+Inlined$package$
+Object
+covtest.Inlined$package$
+testInlined
 155
 162
 6
@@ -69,7 +86,7 @@ false
 false
 List(l)
 
-3
+4
 Inlined.scala
 covtest
 Inlined$package$
@@ -86,7 +103,7 @@ false
 false
 List
 
-4
+5
 Inlined.scala
 covtest
 Inlined$package$
@@ -103,7 +120,7 @@ false
 false
 List(l).length
 
-5
+6
 Inlined.scala
 covtest
 Inlined$package$
@@ -120,7 +137,7 @@ false
 false
 scala.runtime.Scala3RunTime.assertFailed()
 
-6
+7
 Inlined.scala
 covtest
 Inlined$package$
@@ -137,7 +154,24 @@ true
 false
 scala.runtime.Scala3RunTime.assertFailed()
 
-7
+8
+Inlined.scala
+covtest
+Inlined$package$
+Object
+covtest.Inlined$package$
+testInlined
+330
+330
+10
+<none>
+Literal
+true
+0
+false
+
+
+9
 Inlined.scala
 covtest
 Inlined$package$
@@ -154,7 +188,7 @@ false
 false
 List(l)
 
-8
+10
 Inlined.scala
 covtest
 Inlined$package$
@@ -171,7 +205,7 @@ false
 false
 List
 
-9
+11
 Inlined.scala
 covtest
 Inlined$package$
@@ -188,7 +222,7 @@ false
 false
 List(l).length
 
-10
+12
 Inlined.scala
 covtest
 Inlined$package$
@@ -205,7 +239,7 @@ false
 false
 scala.runtime.Scala3RunTime.assertFailed()
 
-11
+13
 Inlined.scala
 covtest
 Inlined$package$
@@ -222,7 +256,24 @@ true
 false
 scala.runtime.Scala3RunTime.assertFailed()
 
-12
+14
+Inlined.scala
+covtest
+Inlined$package$
+Object
+covtest.Inlined$package$
+testInlined
+330
+330
+10
+<none>
+Literal
+true
+0
+false
+
+
+15
 Inlined.scala
 covtest
 Inlined$package$

tests/coverage/pos/MatchCaseClasses.scoverage.check

@@ -25,23 +25,6 @@ MatchCaseClasses$
 Object
 covtest.MatchCaseClasses$
 f
-135
-147
-7
-<none>
-Block
-false
-0
-false
-case Pat1(0)
-
-1
-MatchCaseClasses.scala
-covtest
-MatchCaseClasses$
-Object
-covtest.MatchCaseClasses$
-f
 151
 163
 7
@@ -52,24 +35,24 @@ false
 false
 println("a")
 
-2
+1
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
 Object
 covtest.MatchCaseClasses$
 f
-168
-180
-8
+148
+163
+7
 <none>
 Block
-false
+true
 0
 false
-case Pat1(_)
+=> println("a")
 
-3
+2
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
@@ -86,24 +69,24 @@ false
 false
 println("b")
 
-4
+3
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
 Object
 covtest.MatchCaseClasses$
 f
-201
-221
-9
+181
+196
+8
 <none>
 Block
-false
+true
 0
 false
-case p @ Pat2(1, -1)
+=> println("b")
 
-5
+4
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
@@ -120,24 +103,24 @@ false
 false
 println("c")
 
-6
+5
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
 Object
 covtest.MatchCaseClasses$
 f
-242
-265
-10
+222
+237
+9
 <none>
 Block
-false
+true
 0
 false
-case Pat2(_, y: String)
+=> println("c")
 
-7
+6
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
@@ -154,7 +137,7 @@ false
 false
 println(y)
 
-8
+7
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
@@ -171,24 +154,24 @@ false
 false
 println("d")
 
-9
+8
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
 Object
 covtest.MatchCaseClasses$
 f
-309
-321
-13
+275
+304
+11
 <none>
 Block
-false
+true
 0
 false
-case p: Pat2
+println(y)\n      println("d")
 
-10
+9
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
@@ -205,24 +188,24 @@ false
 false
 println("e")
 
-11
+10
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
 Object
 covtest.MatchCaseClasses$
 f
-342
-348
-14
+322
+337
+13
 <none>
 Block
-false
+true
 0
 false
-case _
+=> println("e")
 
-12
+11
 MatchCaseClasses.scala
 covtest
 MatchCaseClasses$
@@ -239,6 +222,23 @@ false
 false
 println("other")
 
+12
+MatchCaseClasses.scala
+covtest
+MatchCaseClasses$
+Object
+covtest.MatchCaseClasses$
+f
+349
+368
+14
+<none>
+Block
+true
+0
+false
+=> println("other")
+
 13
 MatchCaseClasses.scala
 covtest