SI-6686 drop valdef unused in flatMapCond's block

6 files changed, 80 insertions, 81 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
index c6f80c9b20..4b53802d95 100644
--- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
@@ -3792,11 +3792,17 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
         // nextBinder: T
         // next == MatchMonad[U]
         // returns MatchMonad[U]
-        def flatMapCond(cond: Tree, res: Tree, nextBinder: Symbol, next: Tree): Tree =
-          ifThenElseZero(cond, BLOCK(
-            VAL(nextBinder) === res,
-            next
-          ))
+        def flatMapCond(cond: Tree, res: Tree, nextBinder: Symbol, next: Tree): Tree = {
+          val rest =
+            // only emit a local val for `nextBinder` if it's actually referenced in `next`
+            if (next.exists(_.symbol eq nextBinder))
+              BLOCK(
+                VAL(nextBinder) === res,
+                next
+              )
+            else next
+          ifThenElseZero(cond, rest)
+        }
 
         // guardTree: Boolean
         // next: MatchMonad[T]
diff --git a/test/files/jvm/patmat_opt_ignore_underscore/Analyzed_1.scala b/test/files/jvm/patmat_opt_ignore_underscore/Analyzed_1.scala
index ac59e41ba7..fa3639380d 100644
--- a/test/files/jvm/patmat_opt_ignore_underscore/Analyzed_1.scala
+++ b/test/files/jvm/patmat_opt_ignore_underscore/Analyzed_1.scala
@@ -20,7 +20,6 @@ class SameBytecode {
     val x1 = Foo(1, "a")
     if (x1.ne(null)) {
       if (x1.x.isInstanceOf[String]) {
-        val x3 = x1.x.asInstanceOf[String]
         return x1.y
       }
     }
diff --git a/test/files/jvm/patmat_opt_no_nullcheck/Analyzed_1.scala b/test/files/jvm/patmat_opt_no_nullcheck/Analyzed_1.scala
index 1594eb523c..3a594c401e 100644
--- a/test/files/jvm/patmat_opt_no_nullcheck/Analyzed_1.scala
+++ b/test/files/jvm/patmat_opt_no_nullcheck/Analyzed_1.scala
@@ -14,7 +14,6 @@ class SameBytecode {
     if (x1.isInstanceOf[Foo]) {
       val x3 = x1.asInstanceOf[Foo]
       if (x3.x.isInstanceOf[String]) {
-        val x4 = x3.x.asInstanceOf[String]
         val x = ()
         return
       }
diff --git a/test/files/jvm/patmat_opt_primitive_typetest/Analyzed_1.scala b/test/files/jvm/patmat_opt_primitive_typetest/Analyzed_1.scala
index c5b8811449..e5db6c4dd0 100644
--- a/test/files/jvm/patmat_opt_primitive_typetest/Analyzed_1.scala
+++ b/test/files/jvm/patmat_opt_primitive_typetest/Analyzed_1.scala
@@ -16,7 +16,6 @@ class SameBytecode {
   def b: String = {
     val x1 = Foo(1, "a")
     if (x1.ne(null)) {
-      val x3 = x1.x
       return x1.y
     }
 
diff --git a/test/files/run/inline-ex-handlers.check b/test/files/run/inline-ex-handlers.check
index 905dfc3ee7..f2f0b60687 100644
--- a/test/files/run/inline-ex-handlers.check
+++ b/test/files/run/inline-ex-handlers.check
@@ -21,15 +21,15 @@
 <     92	JUMP 7
 <     
 <   7: 
-395c391
+391c387
 <   locals: value args, variable result, value ex6, value x4, value x5, value message, value x
 ---
 >   locals: value args, variable result, value ex6, value x4, value x5, value x
-397c393
+393c389
 <   blocks: [1,2,3,4,5,8,10,11,13]
 ---
 >   blocks: [1,2,3,5,8,10,11,13,14]
-421c417,426
+417c413,422
 <     103	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex6)
@@ -42,39 +42,39 @@
 >     106	LOAD_LOCAL(value x4)
 >     106	IS_INSTANCE REF(class MyException)
 >     106	CZJUMP (BOOL)NE ? 5 : 8
-434,436d438
+430,432d434
 <     101	JUMP 4
 <     
 <   4: 
-446,449d447
+442,445d443
 <     106	LOAD_LOCAL(value x5)
 <     106	CALL_METHOD MyException.message (dynamic)
 <     106	STORE_LOCAL(value message)
 <     106	SCOPE_ENTER value message
-451c449,450
+447c445,446
 <     106	LOAD_LOCAL(value message)
 ---
 >     ?	LOAD_LOCAL(value x5)
 >     106	CALL_METHOD MyException.message (dynamic)
-523c522
+519c518
 <   blocks: [1,2,3,4,6,7,8,9,10]
 ---
 >   blocks: [1,2,3,4,6,7,8,9,10,11,12,13]
-552c551
+548c547
 <     306	THROW(MyException)
 ---
 >     ?	JUMP 11
-553a553,557
+549a549,553
 >   11: 
 >     ?	LOAD_LOCAL(variable monitor4)
 >     305	MONITOR_EXIT
 >     ?	JUMP 12
 >     
-558c562
+554c558
 <     ?	THROW(Throwable)
 ---
 >     ?	JUMP 12
-564c568,575
+560c564,571
 <     ?	THROW(Throwable)
 ---
 >     ?	STORE_LOCAL(value t)
@@ -85,7 +85,7 @@
 >     304	MONITOR_EXIT
 >     ?	STORE_LOCAL(value t)
 >     ?	JUMP 13
-579a591,602
+575a587,598
 >   13: 
 >     310	LOAD_MODULE object Predef
 >     310	CALL_PRIMITIVE(StartConcat)
@@ -98,35 +98,35 @@
 >     310	CALL_METHOD scala.Predef.println (dynamic)
 >     310	JUMP 2
 >     
-588c611
+584c607
 <     catch (Throwable) in ArrayBuffer(7, 8, 9, 10) starting at: 6
 ---
 >     catch (Throwable) in ArrayBuffer(7, 8, 9, 10, 11) starting at: 6
-591c614
+587c610
 <     catch (Throwable) in ArrayBuffer(4, 6, 7, 8, 9, 10) starting at: 3
 ---
 >     catch (Throwable) in ArrayBuffer(4, 6, 7, 8, 9, 10, 11, 12) starting at: 3
-623c646
+619c642
 <   blocks: [1,2,3,4,5,6,7,9,10]
 ---
 >   blocks: [1,2,3,4,5,6,7,9,10,11,12]
-647c670,671
+643c666,667
 <     78	THROW(IllegalArgumentException)
 ---
 >     ?	STORE_LOCAL(value e)
 >     ?	JUMP 11
-648a673,677
+644a669,673
 >   11: 
 >     81	LOAD_LOCAL(value e)
 >     ?	STORE_LOCAL(variable exc1)
 >     ?	JUMP 12
 >     
-676c705,706
+672c701,702
 <     81	THROW(Exception)
 ---
 >     ?	STORE_LOCAL(variable exc1)
 >     ?	JUMP 12
-692a723,735
+688a719,731
 >   12: 
 >     83	LOAD_MODULE object Predef
 >     83	CONSTANT("finally")
@@ -140,19 +140,19 @@
 >     84	LOAD_LOCAL(variable exc1)
 >     84	THROW(Throwable)
 >     
-698c741
+694c737
 <     catch (<none>) in ArrayBuffer(4, 6, 7, 9) starting at: 3
 ---
 >     catch (<none>) in ArrayBuffer(4, 6, 7, 9, 11) starting at: 3
-722c765
+718c761
 <   locals: value args, variable result, value ex6, variable exc2, value x4, value x5, value message, value x, value ex6, value x4, value x5, value message, value x
 ---
 >   locals: value args, variable result, value ex6, variable exc2, value x4, value x5, value x, value ex6, value x4, value x5, value x
-724c767
+720c763
 <   blocks: [1,2,3,4,5,6,9,11,14,15,16,19,21,22,24,25]
 ---
 >   blocks: [1,2,3,4,5,6,9,11,14,15,16,19,21,22,24,25,26,27,28]
-748c791,798
+744c787,794
 <     172	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex6)
@@ -163,64 +163,64 @@
 >     170	STORE_LOCAL(value x4)
 >     170	SCOPE_ENTER value x4
 >     170	JUMP 15
-791,794d840
+787,790d836
 <     175	LOAD_LOCAL(value x5)
 <     175	CALL_METHOD MyException.message (dynamic)
 <     175	STORE_LOCAL(value message)
 <     175	SCOPE_ENTER value message
-796c842,843
+792c838,839
 <     176	LOAD_LOCAL(value message)
 ---
 >     ?	LOAD_LOCAL(value x5)
 >     176	CALL_METHOD MyException.message (dynamic)
-800c847,848
+796c843,844
 <     177	LOAD_LOCAL(value message)
 ---
 >     ?	LOAD_LOCAL(value x5)
 >     177	CALL_METHOD MyException.message (dynamic)
-802c850,851
+798c846,847
 <     177	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex6)
 >     ?	JUMP 27
-806c855,856
+802c851,852
 <     170	THROW(Throwable)
 ---
 >     ?	STORE_LOCAL(value ex6)
 >     ?	JUMP 27
-815a866,871
+811a862,867
 >   27: 
 >     169	LOAD_LOCAL(value ex6)
 >     169	STORE_LOCAL(value x4)
 >     169	SCOPE_ENTER value x4
 >     169	JUMP 5
 >     
-826,829d881
+822,825d877
 <     180	LOAD_LOCAL(value x5)
 <     180	CALL_METHOD MyException.message (dynamic)
 <     180	STORE_LOCAL(value message)
 <     180	SCOPE_ENTER value message
-831c883,884
+827c879,880
 <     181	LOAD_LOCAL(value message)
 ---
 >     ?	LOAD_LOCAL(value x5)
 >     181	CALL_METHOD MyException.message (dynamic)
-835c888,889
+831c884,885
 <     182	LOAD_LOCAL(value message)
 ---
 >     ?	LOAD_LOCAL(value x5)
 >     182	CALL_METHOD MyException.message (dynamic)
-837c891,892
+833c887,888
 <     182	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(variable exc2)
 >     ?	JUMP 28
-841c896,897
+837c892,893
 <     169	THROW(Throwable)
 ---
 >     ?	STORE_LOCAL(variable exc2)
 >     ?	JUMP 28
-857a914,926
+853a910,922
 >   28: 
 >     184	LOAD_MODULE object Predef
 >     184	CONSTANT("finally")
@@ -234,23 +234,23 @@
 >     185	LOAD_LOCAL(variable exc2)
 >     185	THROW(Throwable)
 >     
-863c932
+859c928
 <     catch (Throwable) in ArrayBuffer(14, 15, 16, 19, 21, 22, 24) starting at: 4
 ---
 >     catch (Throwable) in ArrayBuffer(14, 15, 16, 19, 21, 22, 24, 26) starting at: 4
-866c935
+862c931
 <     catch (<none>) in ArrayBuffer(4, 5, 6, 9, 14, 15, 16, 19, 21, 22, 24) starting at: 3
 ---
 >     catch (<none>) in ArrayBuffer(4, 5, 6, 9, 14, 15, 16, 19, 21, 22, 24, 26, 27) starting at: 3
-890c959
+886c955
 <   locals: value args, variable result, value e, value ex6, value x4, value x5, value message, value x
 ---
 >   locals: value args, variable result, value e, value ex6, value x4, value x5, value x
-892c961
+888c957
 <   blocks: [1,2,3,6,7,8,11,13,14,16]
 ---
 >   blocks: [1,2,3,6,7,8,11,13,14,16,17]
-916c985,992
+912c981,988
 <     124	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex6)
@@ -261,29 +261,29 @@
 >     122	STORE_LOCAL(value x4)
 >     122	SCOPE_ENTER value x4
 >     122	JUMP 7
-941,944d1016
+937,940d1012
 <     127	LOAD_LOCAL(value x5)
 <     127	CALL_METHOD MyException.message (dynamic)
 <     127	STORE_LOCAL(value message)
 <     127	SCOPE_ENTER value message
-946c1018,1019
+942c1014,1015
 <     127	LOAD_LOCAL(value message)
 ---
 >     ?	LOAD_LOCAL(value x5)
 >     127	CALL_METHOD MyException.message (dynamic)
-975c1048
+971c1044
 <     catch (IllegalArgumentException) in ArrayBuffer(6, 7, 8, 11, 13, 14, 16) starting at: 3
 ---
 >     catch (IllegalArgumentException) in ArrayBuffer(6, 7, 8, 11, 13, 14, 16, 17) starting at: 3
-999c1072
+995c1068
 <   locals: value args, variable result, value ex6, value x4, value x5, value message, value x, value e
 ---
 >   locals: value args, variable result, value ex6, value x4, value x5, value x, value e
-1001c1074
+997c1070
 <   blocks: [1,2,3,4,5,8,12,13,14,16]
 ---
 >   blocks: [1,2,3,5,8,12,13,14,16,17]
-1025c1098,1107
+1021c1094,1103
 <     148	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex6)
@@ -296,25 +296,25 @@
 >     154	LOAD_LOCAL(value x4)
 >     154	IS_INSTANCE REF(class MyException)
 >     154	CZJUMP (BOOL)NE ? 5 : 8
-1046,1048d1127
+1042,1044d1123
 <     145	JUMP 4
 <     
 <   4: 
-1058,1061d1136
+1054,1057d1132
 <     154	LOAD_LOCAL(value x5)
 <     154	CALL_METHOD MyException.message (dynamic)
 <     154	STORE_LOCAL(value message)
 <     154	SCOPE_ENTER value message
-1063c1138,1139
+1059c1134,1135
 <     154	LOAD_LOCAL(value message)
 ---
 >     ?	LOAD_LOCAL(value x5)
 >     154	CALL_METHOD MyException.message (dynamic)
-1280c1356
+1276c1352
 <   blocks: [1,2,3,4,5,7]
 ---
 >   blocks: [1,2,3,4,5,7,8]
-1304c1380,1387
+1300c1376,1383
 <     38	THROW(IllegalArgumentException)
 ---
 >     ?	STORE_LOCAL(value e)
@@ -325,20 +325,20 @@
 >     42	CONSTANT("IllegalArgumentException")
 >     42	CALL_METHOD scala.Predef.println (dynamic)
 >     42	JUMP 2
-1351c1434
+1347c1430
 <   locals: value args, variable result, value ex6, value x4, value x5, value message, value x
 ---
 >   locals: value args, variable result, value ex6, value x4, value x5, value x
-1353c1436
+1349c1432
 <   blocks: [1,2,3,4,5,8,10,11,13,14,16]
 ---
 >   blocks: [1,2,3,5,8,10,11,13,14,16,17]
-1377c1460,1461
+1373c1456,1457
 <     203	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex6)
 >     ?	JUMP 17
-1397c1481,1490
+1393c1477,1486
 <     209	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex6)
@@ -351,41 +351,41 @@
 >     212	LOAD_LOCAL(value x4)
 >     212	IS_INSTANCE REF(class MyException)
 >     212	CZJUMP (BOOL)NE ? 5 : 8
-1410,1412d1502
+1406,1408d1498
 <     200	JUMP 4
 <     
 <   4: 
-1422,1425d1511
+1418,1421d1507
 <     212	LOAD_LOCAL(value x5)
 <     212	CALL_METHOD MyException.message (dynamic)
 <     212	STORE_LOCAL(value message)
 <     212	SCOPE_ENTER value message
-1427c1513,1514
+1423c1509,1510
 <     213	LOAD_LOCAL(value message)
 ---
 >     ?	LOAD_LOCAL(value x5)
 >     213	CALL_METHOD MyException.message (dynamic)
-1471c1558
+1467c1554
 <   blocks: [1,2,3,4,5,7]
 ---
 >   blocks: [1,2,3,4,5,7,8]
-1495c1582,1583
+1491c1578,1579
 <     58	THROW(IllegalArgumentException)
 ---
 >     ?	STORE_LOCAL(value e)
 >     ?	JUMP 8
-1496a1585,1590
+1492a1581,1586
 >   8: 
 >     62	LOAD_MODULE object Predef
 >     62	CONSTANT("RuntimeException")
 >     62	CALL_METHOD scala.Predef.println (dynamic)
 >     62	JUMP 2
 >     
-1544c1638
+1540c1634
 <   blocks: [1,2,3,4]
 ---
 >   blocks: [1,2,3,4,5]
-1564c1658,1663
+1560c1654,1659
 <     229	THROW(MyException)
 ---
 >     ?	JUMP 5
@@ -394,19 +394,19 @@
 >     ?	LOAD_LOCAL(variable monitor1)
 >     228	MONITOR_EXIT
 >     228	THROW(Throwable)
-1570c1669
+1566c1665
 <     ?	THROW(Throwable)
 ---
 >     228	THROW(Throwable)
-1598c1697
+1594c1693
 <   locals: value args, variable result, variable monitor2, variable monitorResult1
 ---
 >   locals: value exception$1, value args, variable result, variable monitor2, variable monitorResult1
-1600c1699
+1596c1695
 <   blocks: [1,2,3,4]
 ---
 >   blocks: [1,2,3,4,5]
-1623c1722,1730
+1619c1718,1726
 <     245	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value exception$1)
@@ -418,7 +418,7 @@
 >     ?	LOAD_LOCAL(variable monitor2)
 >     244	MONITOR_EXIT
 >     244	THROW(Throwable)
-1629c1736
+1625c1732
 <     ?	THROW(Throwable)
 ---
 >     244	THROW(Throwable)
diff --git a/test/files/run/t6288b-jump-position.check b/test/files/run/t6288b-jump-position.check
index 45ec31c308..ece88b18f0 100644
--- a/test/files/run/t6288b-jump-position.check
+++ b/test/files/run/t6288b-jump-position.check
@@ -19,7 +19,7 @@ object Case3 extends Object {
   Exception handlers: 
     
   def main(args: Array[String] (ARRAY[REF(class String)])): Unit {
-  locals: value args, value x1, value x2, value x
+  locals: value args, value x1, value x
   startBlock: 1
   blocks: [1,2,3,6,7]
   
@@ -35,10 +35,6 @@ object Case3 extends Object {
     5	CZJUMP (BOOL)NE ? 3 : 6
     
   3: 
-    5	LOAD_LOCAL(value x1)
-    5	CHECK_CAST REF(class String)
-    5	STORE_LOCAL(value x2)
-    5	SCOPE_ENTER value x2
     6	LOAD_MODULE object Predef
     6	CONSTANT("case 0")
     6	CALL_METHOD scala.Predef.println (dynamic)