From 6192a6a7f8507d17a6854412fc9a7a97babdf448 Mon Sep 17 00:00:00 2001
From: Chris Pressey <cpressey@catseye.tc>
Date: Fri, 16 Oct 2015 09:38:38 +0100
Subject: [PATCH] Add specific error for uninit outputs.  Sketch `if` analysis.

---
 src/sixtypical/analyzer.py   | 17 +++++++++++++----
 tests/SixtyPical Analysis.md | 20 ++++++++++----------
 2 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/src/sixtypical/analyzer.py b/src/sixtypical/analyzer.py
index 71e3a1b..817b039 100644
--- a/src/sixtypical/analyzer.py
+++ b/src/sixtypical/analyzer.py
@@ -18,6 +18,10 @@ class UninitializedAccessError(StaticAnalysisError):
     pass
 
 
+class UninitializedOutputError(StaticAnalysisError):
+    pass
+
+
 class IllegalWriteError(StaticAnalysisError):
     pass
 
@@ -44,13 +48,14 @@ class Context():
             self._store.setdefault(ref.name, UNINITIALIZED)
             self._writeables.add(ref.name)
 
-    def assertInitialized(self, *refs):
+    def assertInitialized(self, *refs, **kwargs):
+        exception_class = kwargs.get('exception_class', UninitializedAccessError)
         for ref in refs:
             if isinstance(ref, ConstantRef):
                 pass
             elif isinstance(ref, LocationRef):
                 if self.get(ref) != INITIALIZED:
-                    raise UninitializedAccessError(ref.name)
+                    raise exception_class(ref.name)
             else:
                 raise ValueError(ref)
 
@@ -94,7 +99,7 @@ def analyze_routine(routine, routines):
     context = Context(routine.inputs, routine.outputs, routine.trashes)
     analyze_block(routine.block, context, routines)
     for ref in routine.outputs:
-        context.assertInitialized(ref)
+        context.assertInitialized(ref, exception_class=UninitializedOutputError)
 
 
 def analyze_block(block, context, routines):
@@ -154,6 +159,10 @@ def analyze_instr(instr, context, routines):
             context.assertWriteable(ref)
             context.setUninitialized(ref)
     elif opcode == 'if':
-        pass
+        context1 = context.clone()
+        context2 = context.clone()
+        analyze_block(instr.block1, context1, routines)
+        analyze_block(instr.block2, context2, routines)
+        reconcile_contexts(context1, context2, output=context)
     else:
         raise NotImplementedError
diff --git a/tests/SixtyPical Analysis.md b/tests/SixtyPical Analysis.md
index 7f90117..3c8478e 100644
--- a/tests/SixtyPical Analysis.md	
+++ b/tests/SixtyPical Analysis.md	
@@ -1,15 +1,15 @@
-Sixtypical Analysis
+SixtyPical Analysis
 ===================
 
-This is a test suite, written in [Falderal][] format, for the Sixtypical
+This is a test suite, written in [Falderal][] format, for the SixtyPical
 static analysis rules.
 
 [Falderal]:     http://catseye.tc/node/Falderal
 
-    -> Functionality "Analyze Sixtypical program" is implemented by
+    -> Functionality "Analyze SixtyPical program" is implemented by
     -> shell command "bin/sixtypical --analyze %(test-body-file)"
 
-    -> Tests for functionality "Analyze Sixtypical program"
+    -> Tests for functionality "Analyze SixtyPical program"
 
 ### Rudiments ###
 
@@ -42,7 +42,7 @@ If a routine declares it outputs a location, that location should be initialized
     | {
     |     ld x, 0
     | }
-    ? UninitializedAccessError: a
+    ? UninitializedOutputError: a
 
     | routine main
     |   inputs a
@@ -318,7 +318,7 @@ You can't output a value that the thing you called trashed.
     |     ld x, 0
     |     call foo
     | }
-    ? UninitializedAccessError: lives
+    ? UninitializedOutputError: lives
 
 ...unless you write to it yourself afterwards.
 
@@ -402,14 +402,14 @@ Both blocks of an `if` are analyzed.
 
     | routine foo
     |   inputs a
-    |   outputs a
-    |   trashes z, n, c
+    |   outputs x
+    |   trashes a, z, n, c
     | {
     |     cmp a, 42
     |     if z {
-    |         ld a, 7
+    |         ld x, 7
     |     } else {
-    |         ld a, 23
+    |         ld x, 23
     |     }
     | }
     = ok