From 9afb9275cc762ae935ef7f0e8946a934e6e70545 Mon Sep 17 00:00:00 2001
From: Jean Privat <jean@pryen.org>
Date: Wed, 17 Jun 2009 16:38:07 -0400
Subject: [PATCH] syntax: add PExpr:is_typed and PExpr::is_statement

Contracts are not enforced yet.
Update check_expr to profit from them.

Signed-off-by: Jean Privat <jean@pryen.org>
---
 src/syntax/syntax_base.nit |   22 +++++++++++++++++-----
 src/syntax/typing.nit      |   10 ++++++++--
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/syntax/syntax_base.nit b/src/syntax/syntax_base.nit
index 259cf9a..aaa9439 100644
--- a/src/syntax/syntax_base.nit
+++ b/src/syntax/syntax_base.nit
@@ -373,9 +373,12 @@ special Visitor
 	# Require that the static type of n is known
 	meth check_expr(n: PExpr): Bool
 	do
-		# FIXME: The tc.error_count is a workaround since currently there is no way
-		# to distingate statements from buggy expressions: both have a null stype
-		if tc.error_count == 0 and n.stype == null then
+		if not n.is_typed then
+			# An error occured in a sub node,
+			# sillently cascade fail
+			return false
+		else if tc.error_count == 0 and n.is_statement then # FIXME remove 'tc.error_count == 0'
+		#if tc.error_count == 0 and n.stype == null then
 			error(n, "Type error: expected expression.")
 			return false
 		end
@@ -624,8 +627,17 @@ redef class AType
 end
 
 redef class PExpr
-	# Static type
-	# Is null for statement and for erronus expression
+	# Is the expression node correcly typed
+	# Return false if typed was not yet computed or
+	# if an error occured during the typing computation
+	meth is_typed: Bool is abstract
+
+	# Is the expression node a statement? (ie has no return value)
+	# require: is_typed
+	meth is_statement: Bool is abstract
+
+	# The static type of the expression
+	# require: is_typed and not is_statement
 	meth stype: MMType is abstract
 end
 
diff --git a/src/syntax/typing.nit b/src/syntax/typing.nit
index 2bf36f4..91e3043 100644
--- a/src/syntax/typing.nit
+++ b/src/syntax/typing.nit
@@ -345,8 +345,14 @@ redef class PType
 end
 
 redef class PExpr
-	redef readable attr _stype: MMType
-	
+	redef readable attr _is_typed: Bool = true # FIXME: Switch to false once subclasses are adapted
+	redef meth is_statement: Bool do return _stype == null
+	redef meth stype
+	do
+		return _stype
+	end
+	attr _stype: MMType
+
 	# Is the expression the implicit receiver
 	meth is_implicit_self: Bool do return false
 
-- 
1.7.9.5