From f430bf3f638b793d7365a8fcd5abc4cd060eec59 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Mon, 29 Jun 2015 00:31:06 +0300
Subject: [PATCH] Add support for exceptions.

---
 artiq/py2llvm/asttyped.py                  |  4 +++
 artiq/py2llvm/builtins.py                  |  2 +-
 artiq/py2llvm/types.py                     |  3 ++
 artiq/py2llvm/typing.py                    | 41 +++++++++++++++++++++-
 lit-test/py2llvm/typing/error_exception.py | 14 ++++++++
 lit-test/py2llvm/typing/exception.py       |  8 +++++
 6 files changed, 70 insertions(+), 2 deletions(-)
 create mode 100644 lit-test/py2llvm/typing/error_exception.py

diff --git a/artiq/py2llvm/asttyped.py b/artiq/py2llvm/asttyped.py
index a9762ac4e..c592161e6 100644
--- a/artiq/py2llvm/asttyped.py
+++ b/artiq/py2llvm/asttyped.py
@@ -33,6 +33,10 @@ class FunctionDefT(ast.FunctionDef, scoped):
 class ModuleT(ast.Module, scoped):
     pass
 
+class ExceptHandlerT(ast.ExceptHandler, commontyped):
+    _fields = ("filter", "name", "body") # rename ast.ExceptHandler.type
+    _types = ("name_type",)
+
 class AttributeT(ast.Attribute, commontyped):
     pass
 class BinOpT(ast.BinOp, commontyped):
diff --git a/artiq/py2llvm/builtins.py b/artiq/py2llvm/builtins.py
index c1dcfb7ba..9e44e0da7 100644
--- a/artiq/py2llvm/builtins.py
+++ b/artiq/py2llvm/builtins.py
@@ -125,7 +125,7 @@ def is_builtin(typ, name):
     return isinstance(typ, types.TBuiltin) and \
         typ.name == name
 
-def is_exception(typ, name=None):
+def is_exn_constructor(typ, name=None):
     typ = typ.find()
     if name is not None:
         return isinstance(typ, types.TExceptionConstructor) and \
diff --git a/artiq/py2llvm/types.py b/artiq/py2llvm/types.py
index 4f1bc4dfc..388b1d6ff 100644
--- a/artiq/py2llvm/types.py
+++ b/artiq/py2llvm/types.py
@@ -227,6 +227,9 @@ class TExceptionConstructor(TBuiltin):
     Note that this is not the same as the type of an instance of
     the class, which is ``TMono("Exception", ...)``.
     """
+    def to_exception_type(self):
+        # Exceptions currently can't have type parameters
+        return TMono(self.name, {})
 
 class TValue(Type):
     """
diff --git a/artiq/py2llvm/typing.py b/artiq/py2llvm/typing.py
index f16191fd8..dc4ffdb33 100644
--- a/artiq/py2llvm/typing.py
+++ b/artiq/py2llvm/typing.py
@@ -328,6 +328,15 @@ class ASTTypedRewriter(algorithm.Transformer):
         finally:
             self.env_stack.pop()
 
+    def visit_ExceptHandler(self, node):
+        node = self.generic_visit(node)
+        node = asttyped.ExceptHandlerT(
+            name_type=self._find_name(node.name, node.name_loc),
+            filter=node.type, name=node.name, body=node.body,
+            except_loc=node.except_loc, as_loc=node.as_loc, name_loc=node.name_loc,
+            colon_loc=node.colon_loc, loc=node.loc)
+        return node
+
     def visit_Raise(self, node):
         node = self.generic_visit(node)
         if node.cause:
@@ -363,7 +372,6 @@ class ASTTypedRewriter(algorithm.Transformer):
     visit_Delete = visit_unsupported
     visit_Import = visit_unsupported
     visit_ImportFrom = visit_unsupported
-    visit_Try = visit_unsupported
 
 
 class Inferencer(algorithm.Visitor):
@@ -1070,6 +1078,30 @@ class Inferencer(algorithm.Visitor):
                 node.context_expr.loc)
             self.engine.process(diag)
 
+    def visit_ExceptHandlerT(self, node):
+        self.generic_visit(node)
+
+        if not builtins.is_exn_constructor(node.filter.type):
+            diag = diagnostic.Diagnostic("error",
+                "this expression must refer to an exception constructor",
+                {"type": types.TypePrinter().name(node.filter.type)},
+                node.filter.loc)
+            self.engine.process(diag)
+        else:
+            def makenotes(printer, typea, typeb, loca, locb):
+                return [
+                    diagnostic.Diagnostic("note",
+                        "expression of type {typea}",
+                        {"typea": printer.name(typea)},
+                        loca),
+                    diagnostic.Diagnostic("note",
+                        "constructor of an exception of type {typeb}",
+                        {"typeb": printer.name(typeb)},
+                        locb)
+                ]
+            self._unify(node.name_type, node.filter.type.to_exception_type(),
+                        node.name_loc, node.filter.loc, makenotes)
+
     def _type_from_arguments(self, node, ret):
         self.generic_visit(node)
 
@@ -1166,6 +1198,13 @@ class Printer(algorithm.Visitor):
         self.rewriter.insert_before(node.colon_loc,
                                     "->{}".format(self.type_printer.name(node.return_type)))
 
+    def visit_ExceptHandlerT(self, node):
+        super().generic_visit(node)
+
+        if node.name_loc:
+            self.rewriter.insert_after(node.name_loc,
+                                        ":{}".format(self.type_printer.name(node.name_type)))
+
     def generic_visit(self, node):
         super().generic_visit(node)
 
diff --git a/lit-test/py2llvm/typing/error_exception.py b/lit-test/py2llvm/typing/error_exception.py
new file mode 100644
index 000000000..e418b9b8a
--- /dev/null
+++ b/lit-test/py2llvm/typing/error_exception.py
@@ -0,0 +1,14 @@
+# RUN: %python -m artiq.py2llvm.typing +diag %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+try:
+    pass
+# CHECK-L: ${LINE:+1}: error: this expression must refer to an exception constructor
+except 1:
+    pass
+
+try:
+    pass
+# CHECK-L: ${LINE:+1}: error: cannot unify int(width='a) with Exception
+except Exception as e:
+    e = 1
diff --git a/lit-test/py2llvm/typing/exception.py b/lit-test/py2llvm/typing/exception.py
index 5500d96a0..e7ce38b8d 100644
--- a/lit-test/py2llvm/typing/exception.py
+++ b/lit-test/py2llvm/typing/exception.py
@@ -3,3 +3,11 @@
 
 # CHECK-L: Exception:<constructor Exception>
 Exception
+
+try:
+    pass
+except Exception:
+    pass
+except Exception as e:
+    # CHECK-L: e:Exception
+    e