From cc228376275f4294da2a72038297e79989990f2a Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Sat, 16 Jan 2016 03:09:03 +0000
Subject: [PATCH] transforms.inferencer: infer a monomorphic type for slice ":"

---
 artiq/compiler/transforms/inferencer.py | 16 ++++++++++------
 lit-test/test/inferencer/slice.py       |  6 ++++++
 2 files changed, 16 insertions(+), 6 deletions(-)
 create mode 100644 lit-test/test/inferencer/slice.py

diff --git a/artiq/compiler/transforms/inferencer.py b/artiq/compiler/transforms/inferencer.py
index e2f9b5efd..2a95c01e1 100644
--- a/artiq/compiler/transforms/inferencer.py
+++ b/artiq/compiler/transforms/inferencer.py
@@ -202,12 +202,16 @@ class Inferencer(algorithm.Visitor):
                         value.loc, None)
 
     def visit_SliceT(self, node):
-        self._unify(node.type, builtins.TInt(),
-                    node.loc, None)
-        for operand in (node.lower, node.upper, node.step):
-            if operand is not None:
-                self._unify(operand.type, node.type,
-                            operand.loc, None)
+        if (node.lower, node.upper, node.step) == (None, None, None):
+            self._unify(node.type, builtins.TInt32(),
+                        node.loc, None)
+        else:
+            self._unify(node.type, builtins.TInt(),
+                        node.loc, None)
+            for operand in (node.lower, node.upper, node.step):
+                if operand is not None:
+                    self._unify(operand.type, node.type,
+                                operand.loc, None)
 
     def visit_ExtSlice(self, node):
         diag = diagnostic.Diagnostic("error",
diff --git a/lit-test/test/inferencer/slice.py b/lit-test/test/inferencer/slice.py
new file mode 100644
index 000000000..1693bcd85
--- /dev/null
+++ b/lit-test/test/inferencer/slice.py
@@ -0,0 +1,6 @@
+# RUN: %python -m artiq.compiler.testbench.inferencer %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+x = [0]
+# CHECK-L: [::int(width=32)]
+x[:] = [1]