syntax: var assignment can bypass casted type

If rvalue is conform with casted type then
  variable remains casted
else if rvalue is conform with base type then
  # It is the novelty
  variable is (up)casted to its base type
else error

Example:
  var x: T
  x.u_only_method # error
  assert x isa U
  x.u_only_method # ok
  x = a_t # ok
  x.u_only_method # error

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/syntax/typing.nit b/src/syntax/typing.nit
index 4300a8f..679b88e 100644 (file)
--- a/src/syntax/typing.nit
+++ b/src/syntax/typing.nit
@@ -544,7 +544,12 @@ redef class AVarAssignExpr
        do
                v.variable_ctx.mark_is_set(variable)
                var t = v.variable_ctx.stype(variable)
-               v.check_conform_expr(n_value, t)
+               if v.check_conform_expr(n_value, variable.stype) then
+                       # Fall back to base type if current type does not match
+                       if not n_value.stype < t then
+                               v.variable_ctx.stype(variable) = variable.stype
+                       end
+               end
                _is_typed = true
        end
 end
@@ -584,7 +589,12 @@ redef class AVarReassignExpr
                var t = v.variable_ctx.stype(variable)
                var t2 = do_rvalue_typing(v, t)
                if t2 == null then return
-               v.check_conform(self, t2, n_value.stype)
+               if v.check_conform(self, t2, variable.stype) then
+                       # Fall back to base type if current type does not match
+                       if not t2 < t then
+                               v.variable_ctx.stype(variable) = variable.stype
+                       end
+               end
                _is_typed = true
        end
 end

diff --git a/tests/base_isa_cast2.nit b/tests/base_isa_cast2.nit
new file mode 100644 (file)
index 0000000..4bccc58
--- /dev/null
+++ b/tests/base_isa_cast2.nit
@@ -0,0 +1,62 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Copyright 2009 Jean Privat <jean@pryen.org>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import kernel
+
+class A
+       init do end
+end
+
+class B
+special A
+       meth foo(i: Int) do i.output
+       init do end
+end
+
+var a: A = new B
+if a isa B then
+       a.foo(1)
+       a = new B
+       a.foo(2)
+       a = new A
+       #alt1#a.foo(-1)
+else
+#alt2#a.foo(-2)
+end
+#alt3#a.foo(-3)
+
+if not a isa B then
+       #alt4#a.foo(-4)
+       a = new B
+       assert a isa B
+       a.foo(3)
+end
+#alt8#a.foo(4)
+
+while a isa B do
+       #alt8#a.foo(5)
+       a = new A
+       #alt5#a.foo(-5)
+end
+#alt6#a.foo(-6)
+
+while not a isa B do
+       #alt7#a.foo(-7)
+       a = new B
+       assert a isa B
+       a.foo(6)
+end
+#alt8#a.foo(7)

diff --git a/tests/sav/base_isa_cast2.sav b/tests/sav/base_isa_cast2.sav
new file mode 100644 (file)
index 0000000..c65db77
--- /dev/null
+++ b/tests/sav/base_isa_cast2.sav
@@ -0,0 +1,4 @@
+1
+2
+3
+6

diff --git a/tests/sav/base_isa_cast2_alt1.sav b/tests/sav/base_isa_cast2_alt1.sav
new file mode 100644 (file)
index 0000000..148bc33
--- /dev/null
+++ b/tests/sav/base_isa_cast2_alt1.sav
@@ -0,0 +1 @@
+alt/base_isa_cast2_alt1.nit:35,2--9: Error: Method 'foo' doesn't exists in A.

diff --git a/tests/sav/base_isa_cast2_alt2.sav b/tests/sav/base_isa_cast2_alt2.sav
new file mode 100644 (file)
index 0000000..9e5a166
--- /dev/null
+++ b/tests/sav/base_isa_cast2_alt2.sav
@@ -0,0 +1 @@
+alt/base_isa_cast2_alt2.nit:37,1--8: Error: Method 'foo' doesn't exists in A.

diff --git a/tests/sav/base_isa_cast2_alt3.sav b/tests/sav/base_isa_cast2_alt3.sav
new file mode 100644 (file)
index 0000000..65186d9
--- /dev/null
+++ b/tests/sav/base_isa_cast2_alt3.sav
@@ -0,0 +1 @@
+alt/base_isa_cast2_alt3.nit:39,1--8: Error: Method 'foo' doesn't exists in A.

diff --git a/tests/sav/base_isa_cast2_alt4.sav b/tests/sav/base_isa_cast2_alt4.sav
new file mode 100644 (file)
index 0000000..3d2c680
--- /dev/null
+++ b/tests/sav/base_isa_cast2_alt4.sav
@@ -0,0 +1 @@
+alt/base_isa_cast2_alt4.nit:42,2--9: Error: Method 'foo' doesn't exists in A.

diff --git a/tests/sav/base_isa_cast2_alt5.sav b/tests/sav/base_isa_cast2_alt5.sav
new file mode 100644 (file)
index 0000000..0b93912
--- /dev/null
+++ b/tests/sav/base_isa_cast2_alt5.sav
@@ -0,0 +1 @@
+alt/base_isa_cast2_alt5.nit:52,2--9: Error: Method 'foo' doesn't exists in A.

diff --git a/tests/sav/base_isa_cast2_alt6.sav b/tests/sav/base_isa_cast2_alt6.sav
new file mode 100644 (file)
index 0000000..21595bf
--- /dev/null
+++ b/tests/sav/base_isa_cast2_alt6.sav
@@ -0,0 +1 @@
+alt/base_isa_cast2_alt6.nit:54,1--8: Error: Method 'foo' doesn't exists in A.

diff --git a/tests/sav/base_isa_cast2_alt7.sav b/tests/sav/base_isa_cast2_alt7.sav
new file mode 100644 (file)
index 0000000..33bd723
--- /dev/null
+++ b/tests/sav/base_isa_cast2_alt7.sav
@@ -0,0 +1 @@
+alt/base_isa_cast2_alt7.nit:57,2--9: Error: Method 'foo' doesn't exists in A.

diff --git a/tests/sav/base_isa_cast2_alt8.sav b/tests/sav/base_isa_cast2_alt8.sav
new file mode 100644 (file)
index 0000000..c378c50
--- /dev/null
+++ b/tests/sav/base_isa_cast2_alt8.sav
@@ -0,0 +1,3 @@
+alt/base_isa_cast2_alt8.nit:47,1--7: Error: Method 'foo' doesn't exists in A.
+alt/base_isa_cast2_alt8.nit:50,2--8: Error: Method 'foo' doesn't exists in A.
+alt/base_isa_cast2_alt8.nit:62,1--7: Error: Method 'foo' doesn't exists in A.