From 148c7598fdd52d9d0faa09de897a93ee64404733 Mon Sep 17 00:00:00 2001
From: Dan Gooding <dan.gooding2000@gmail.com>
Date: Tue, 3 May 2022 21:46:50 +0100
Subject: [PATCH 1/3] Add test of `under`'s masking when perform `fun` in-place

---
 compile.sh                           |  2 +-
 test/semantics/under-mask.t/run.t    |  9 +++++++++
 test/semantics/under-mask.t/under.kk | 28 ++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 test/semantics/under-mask.t/run.t
 create mode 100644 test/semantics/under-mask.t/under.kk

diff --git a/compile.sh b/compile.sh
index 67549df..f31c241 100755
--- a/compile.sh
+++ b/compile.sh
@@ -17,7 +17,7 @@ else
 fi
 
 # intentionally rely on clang to know the system's target triple
-LL_C_FLAGS="-Wall -Wno-override-module -O$OPT_LEVEL"
+LL_C_FLAGS="-Wall -Wno-override-module -O$OPT_LEVEL" # -fno-optimize-sibling-calls
 
 RUNTIME=$PROJECT_ROOT/lib/runtime/runtime.c
 
diff --git a/test/semantics/under-mask.t/run.t b/test/semantics/under-mask.t/run.t
new file mode 100644
index 0000000..7534b5b
--- /dev/null
+++ b/test/semantics/under-mask.t/run.t
@@ -0,0 +1,9 @@
+`fun` opertions may be run at the perform-site, but they should
+appear to run at the handler-site
+  $ koka-zero interpret under.kk
+  1
+
+  $ export PROJECT_ROOT=../../..
+  $ ../compile.sh under.kk
+  $ ./under
+  1
diff --git a/test/semantics/under-mask.t/under.kk b/test/semantics/under-mask.t/under.kk
new file mode 100644
index 0000000..359f729
--- /dev/null
+++ b/test/semantics/under-mask.t/under.kk
@@ -0,0 +1,28 @@
+effect ask {
+  fun ask(x : ()) : int;
+};
+
+effect fail {
+  control fail(x : ()) : ();
+};
+
+fun main() {
+  with handler {
+    control fail(_) { // fail must be handled here
+      print-int(1)
+    };
+  };
+  with handler {
+    fun ask(_) { // runs in-place at the perform-site of ask(())
+      fail(()); -1;
+     };
+  };
+  with handler {
+    control fail(_) { // fail must not be handled here
+      print-int(0);
+    };
+  };
+  // perform ask(())
+  ask(());
+  ();
+};

From a862eea48d915269662539a26dc46a5209a3bea4 Mon Sep 17 00:00:00 2001
From: Dan Gooding <dan.gooding2000@gmail.com>
Date: Tue, 3 May 2022 22:38:30 +0100
Subject: [PATCH 2/3] Add test which fails to typecheck due occurs check

Perhaps can skip inference phase?
Or else wrap resume into a datatype to hide the recursion
---
 test/semantics/underk-refinding.t/run.t     | 17 ++++++++
 test/semantics/underk-refinding.t/underk.kk | 45 +++++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 test/semantics/underk-refinding.t/run.t
 create mode 100644 test/semantics/underk-refinding.t/underk.kk

diff --git a/test/semantics/underk-refinding.t/run.t b/test/semantics/underk-refinding.t/run.t
new file mode 100644
index 0000000..92f994f
--- /dev/null
+++ b/test/semantics/underk-refinding.t/run.t
@@ -0,0 +1,17 @@
+Fixing the handler-site vector `w_handler` in `under` neglects
+the possiblity of the handler itself being suspended and resumed
+somewhere else.
+
+Taken from Section 2.9.2 of "Generalized Evidence Passing for Effect Handlers
+(or, Efficient Compilation of Effect Handlers to C)"
+by Ningning Xie and Daan Leijen
+
+  $ koka-zero interpret underk.kk
+  1
+  2
+
+  $ export PROJECT_ROOT=../../..
+  $ ../compile.sh underk.kk
+  $ ./underk
+  1
+  2
diff --git a/test/semantics/underk-refinding.t/underk.kk b/test/semantics/underk-refinding.t/underk.kk
new file mode 100644
index 0000000..583c917
--- /dev/null
+++ b/test/semantics/underk-refinding.t/underk.kk
@@ -0,0 +1,45 @@
+effect evil {
+  control evil(x : ()) : ();
+};
+
+// not relevant that `read` is tail-resumptive
+effect read {
+  fun ask(x : ()) : int;
+};
+
+// relevant that `tl` is tail resumptive!
+effect tl {
+  fun tl(x : ()) : int;
+};
+
+// run a resumption under a different handler context
+fun f(k) {
+  with handler { // h_read2
+    fun ask(_) { 2 };
+  };
+  k(()); // 5: resume `evil` now with a different `ask` handler
+};
+
+fun g() {
+  with handler { // h_read1
+    fun ask(_) { 1 };
+  };
+  with handler { // h_evil
+    control evil(_) {
+      // 4: leak resumption to later resume under changed handler context
+      resume; // FIXME: leaking like this fails the occurs check :/
+    };
+  };
+  with handler { // h_tl
+    fun tl(_) {
+      ask(()).print-int(); // 2: receive value 1
+      evil(()); // 3: perform `evil` within tail-resumptive operation clause
+      ask(()).print-int(); // 6: recieve value 2
+    };
+  };
+  tl(); // 1: perform `tl`
+};
+
+fun main() {
+  f(g());
+};

From 4b7d0eee0a722975bcf61e29baa57eea8743fedd Mon Sep 17 00:00:00 2001
From: Dan Gooding <dan.gooding2000@gmail.com>
Date: Tue, 3 May 2022 22:42:04 +0100
Subject: [PATCH 3/3] Revert comment added to compile.sh

---
 compile.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compile.sh b/compile.sh
index f31c241..67549df 100755
--- a/compile.sh
+++ b/compile.sh
@@ -17,7 +17,7 @@ else
 fi
 
 # intentionally rely on clang to know the system's target triple
-LL_C_FLAGS="-Wall -Wno-override-module -O$OPT_LEVEL" # -fno-optimize-sibling-calls
+LL_C_FLAGS="-Wall -Wno-override-module -O$OPT_LEVEL"
 
 RUNTIME=$PROJECT_ROOT/lib/runtime/runtime.c