SI-7605 Deprecate procedure syntax

This commit covers three cases:
- constructor definitions      (def this {...})
- concrete method definitions  (def foo {...})
- abstract method declarations (def foo)

The deprecation is currently hidden behind -Xfuture pending IDE support
for migrating users from procedures to methods.

4 files changed, 27 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index 1d5f35b7d6..07938ec3df 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -2512,7 +2512,11 @@ self =>
           val vparamss = paramClauses(nme.CONSTRUCTOR, classContextBounds map (_.duplicate), ofCaseClass = false)
           newLineOptWhenFollowedBy(LBRACE)
           val rhs = in.token match {
-            case LBRACE   => atPos(in.offset) { constrBlock(vparamss) }
+            case LBRACE   => {
+              if (settings.future)
+                deprecationWarning(in.offset, "Procedure syntax is deprecated. Convert procedure to method by adding `: Unit =`.")
+              atPos(in.offset) { constrBlock(vparamss) }
+            }
             case _        => accept(EQUALS) ; atPos(in.offset) { constrExpr(vparamss) }
           }
           DefDef(mods, nme.CONSTRUCTOR, List(), vparamss, TypeTree(), rhs)
@@ -2538,10 +2542,14 @@ self =>
         var restype = fromWithinReturnType(typedOpt())
         val rhs =
           if (isStatSep || in.token == RBRACE) {
+            if (settings.future)
+              deprecationWarning(in.lastOffset, "Procedure syntax is deprecated. Convert procedure to method by adding `: Unit`.")
             if (restype.isEmpty) restype = scalaUnitConstr
             newmods |= Flags.DEFERRED
             EmptyTree
           } else if (restype.isEmpty && in.token == LBRACE) {
+            if (settings.future)
+              deprecationWarning(in.offset, "Procedure syntax is deprecated. Convert procedure to method by adding `: Unit =`.")
             restype = scalaUnitConstr
             blockExpr()
           } else {
diff --git a/test/files/neg/t7605-deprecation.check b/test/files/neg/t7605-deprecation.check
new file mode 100644
index 0000000000..9c466c058c
--- /dev/null
+++ b/test/files/neg/t7605-deprecation.check
@@ -0,0 +1,12 @@
+t7605-deprecation.scala:2: warning: Procedure syntax is deprecated. Convert procedure to method by adding `: Unit =`.
+  def this(i: Int) { this() }
+                   ^
+t7605-deprecation.scala:3: warning: Procedure syntax is deprecated. Convert procedure to method by adding `: Unit =`.
+  def bar {}
+          ^
+t7605-deprecation.scala:4: warning: Procedure syntax is deprecated. Convert procedure to method by adding `: Unit`.
+  def baz
+         ^
+error: No warnings can be incurred under -Xfatal-warnings.
+three warnings found
+one error found
diff --git a/test/files/neg/t7605-deprecation.flags b/test/files/neg/t7605-deprecation.flags
new file mode 100644
index 0000000000..0a7cb7d202
--- /dev/null
+++ b/test/files/neg/t7605-deprecation.flags
@@ -0,0 +1 @@
+-deprecation -Xfuture -Xfatal-warnings
diff --git a/test/files/neg/t7605-deprecation.scala b/test/files/neg/t7605-deprecation.scala
new file mode 100644
index 0000000000..4a7dcd26d6
--- /dev/null
+++ b/test/files/neg/t7605-deprecation.scala
@@ -0,0 +1,5 @@
+abstract class Foo {
+  def this(i: Int) { this() }
+  def bar {}
+  def baz
+}
\ No newline at end of file