Merge pull request #3736 from tokiwa-software/fix_3734

jvm: Use special value instead of `null` for unit type effect to fix #3734

src/dev/flang/be/jvm/Intrinsix.java

@@ -715,7 +715,9 @@ else if (in.equals("fuzion.sys.internal_array.setel"))
           var arg = args.get(0);
           if (jvm._types.resultType(ecl) == ClassFileConstants.PrimitiveType.type_void)
             {
-              arg = arg.drop().andThen(Expr.ACONST_NULL);
+              arg = arg.drop().andThen(Expr.getstatic(Names.RUNTIME_CLASS,
+                                                      "_UNIT_TYPE_EFFECT_",
+                                                      Names.ANYI_TYPE));
             }
           if (call_t instanceof ClassType call_ct)
             {

src/dev/flang/be/jvm/JVM.java

@@ -607,6 +607,7 @@ void prepare(JVM jvm)
               "dev/flang/be/jvm/runtime/Runtime$2.class",
               "dev/flang/be/jvm/runtime/Runtime$3.class",
               "dev/flang/be/jvm/runtime/Runtime$4.class",
+              "dev/flang/be/jvm/runtime/Runtime$5.class",
               "dev/flang/be/jvm/runtime/Runtime$Abort.class",
               "dev/flang/util/ANY.class",
               "dev/flang/util/Errors.class",

src/dev/flang/be/jvm/runtime/Runtime.java

@@ -125,6 +125,13 @@ private SystemErrNo(final int errno)
   public static final String CLASS_NAME_TO_FUZION_CLAZZ_NAME = "CLASS_NAME_TO_FUZION_CLAZZ_NAME.txt";
 
 
+  /**
+   * Value used for `FuzionThread.effect_store` and `FuzionThread.effect_load`
+   * to distinguish a unit value effect from a not existing effect
+   */
+  public static final AnyI _UNIT_TYPE_EFFECT_ = new AnyI() { };
+
+
   /*--------------------------  static fields  --------------------------*/
 
 
@@ -513,11 +520,11 @@ public static void effect_default(int id, AnyI instance)
 
 
   /**
-   * Helper method to implement intrinsic effect.type.is_installed.
+   * Helper method to implement intrinsic effect.type.is_instated.
    *
    * @param id an effect id.
    *
-   * @return true iff an effect with that id was installed.
+   * @return true iff an effect with that id was instated.
    */
   public static boolean effect_is_instated(int id)
   {
@@ -573,7 +580,7 @@ else if (o != null)
 
 
   /**
-   * Helper method to implement effect.abort.  Abort the currently installed
+   * Helper method to implement effect.abort.  Abort the currently instated
    * effect with given id.  Helper to implement intrinsic effect.abort.
    *
    * @param id the id of the effect type that is aborted.
@@ -585,20 +592,24 @@ public static void effect_abort(int id)
 
 
   /**
-   * Helper method to implement effect.type.instante0.  Install an instance of effect
-   * type specified by id and run f.call while it is installed.  Helper to
+   * Helper method to implement effect.type.instante0.  Instate an instance of effect
+   * type specified by id and run f.call while it is instated.  Helper to
    * implement intrinsic effect.abort.
    *
-   * @param id the id of the effect that is installed
+   * @param id the id of the effect that is instated
    *
-   * @param instance the effect instance that is installed
+   * @param instance the effect instance that is instated, NOTE: This is `_UNIT_TYPE_EFFECT_`
+   * for a unit type effect.
    *
    * @param code the Unary instance to be executed
    *
    * @param call the Java clazz of the Unary instance to be executed.
    */
   public static void effect_instate(int id, AnyI instance, Any code, Class call)
   {
+    if (PRECONDITIONS) require
+      (instance != null);
+
     var t = currentThread();
 
     var old = t.effect_load(id);
@@ -647,14 +658,14 @@ public static void effect_instate(int id, AnyI instance, Any code, Class call)
   }
 
   /**
-   * Helper method to implement `effect.env` expressions.  Returns the installed
+   * Helper method to implement `effect.env` expressions.  Returns the instated
    * effect with the given id.  Causes an error in case no such effect exists.
    *
    * @param id the id of the effect that should be loaded.
    *
-   * @return the instance that was installed for this id
+   * @return the instance that was instated for this id
    *
-   * @throws Error in case no instance was installed.
+   * @throws Error in case no instance was instated.
    */
   public static AnyI effect_get(int id)
   {
@@ -663,7 +674,7 @@ public static AnyI effect_get(int id)
     var result = t.effect_load(id);
     if (result == null)
       {
-        throw new Error("No effect of "+id+" installed");
+        throw new Error("No effect of "+id+" instated");
       }
     return result;
   }

tests/reg_issue3734/Makefile

@@ -0,0 +1,25 @@
+# This file is part of the Fuzion language implementation.
+#
+# The Fuzion language implementation is free software: you can redistribute it
+# and/or modify it under the terms of the GNU General Public License as published
+# by the Free Software Foundation, version 3 of the License.
+#
+# The Fuzion language implementation is distributed in the hope that it will be
+# useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+# License for more details.
+#
+# You should have received a copy of the GNU General Public License along with The
+# Fuzion language implementation.  If not, see <https://www.gnu.org/licenses/>.
+
+
+# -----------------------------------------------------------------------
+#
+#  Tokiwa Software GmbH, Germany
+#
+#  Source code of Fuzion test Makefile
+#
+# -----------------------------------------------------------------------
+
+override NAME = reg_issue3734
+include ../simple.mk

tests/reg_issue3734/reg_issue3734.fz

@@ -0,0 +1,58 @@
+# This file is part of the Fuzion language implementation.
+#
+# The Fuzion language implementation is free software: you can redistribute it
+# and/or modify it under the terms of the GNU General Public License as published
+# by the Free Software Foundation, version 3 of the License.
+#
+# The Fuzion language implementation is distributed in the hope that it will be
+# useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+# License for more details.
+#
+# You should have received a copy of the GNU General Public License along with The
+# Fuzion language implementation.  If not, see <https://www.gnu.org/licenses/>.
+
+
+# -----------------------------------------------------------------------
+#
+#  Tokiwa Software GmbH, Germany
+#
+#  Source code of Fuzion test reg_issue3734
+#
+# -----------------------------------------------------------------------
+
+# This uses an effect without any state, i.e. a unit type value. This used to cause
+# problems with the JVM backend since the unit type value is optimized out and replaced by
+# `null` when calling `Runtime.effect_instate()`, while `null` is used to identify the lack
+# of an installed effect.
+#
+# The fix is to use a special value `Runtime._UUNIT_TYPE_EFFECT_`.
+#
+reg_issue3734 =>
+
+  # the original code from #3734
+  e : effect is
+    stop => e.type.abort e
+
+  codea1 => "hi"
+  codea2 => e.env.stop
+  defa => "ho"
+
+  codeb1 => 42
+  codeb2 => e.env.stop
+  defb => 666
+
+  say (e.instate String e codea1 defa)
+  say (e.instate String e codea2 defa)
+  say (e.instate i32 e codeb1 defb)
+  say (e.instate i32 e codeb2 defb)
+
+  # the simplified example from #3734
+  f : effect is
+
+  f.instate f ()->
+
+    # note that `(3%%4)^` is the identity operation for bool in disguise such that DFA
+    # no longer considers the result `e.is_instated` the constant `true`
+    #
+    say "codea1: "+((3%%4)^f.is_instated)

tests/reg_issue3734/reg_issue3734.fz.expected_out

@@ -0,0 +1,5 @@
+hi
+ho
+42
+666
+codea1: true