syntax: variable assignment can bypass cast

[nit.git] / src / syntax / typing.nit

diff --git a/src/syntax/typing.nit b/src/syntax/typing.nit
index f9d5eba..e7aa1a5 100644 (file)
--- a/src/syntax/typing.nit
+++ b/src/syntax/typing.nit
@@ -46,6 +46,9 @@ special AbsSyntaxVisitor
        # Current knowledge about variables names and types
        readable writable attr _variable_ctx: VariableContext
 
+       # Non-bypassable knowledge about variables names and types
+       readable writable attr _base_variable_ctx: VariableContext
+
        # Current knowledge about escapable blocks
        readable writable attr _escapable_ctx: EscapableContext = new EscapableContext(self)
 
@@ -166,6 +169,7 @@ redef class AMethPropdef
        redef meth accept_typing(v)
        do
                v.variable_ctx = new RootVariableContext(v, self)
+               v.base_variable_ctx = v.variable_ctx
                _self_var = v.self_var
                super
        end
@@ -249,6 +253,8 @@ redef class AClosureDecl
                v.variable_ctx.add(variable)
 
                var old_var_ctx = v.variable_ctx
+               var old_base_var_ctx = v.base_variable_ctx
+               v.base_variable_ctx = v.variable_ctx
                v.variable_ctx = v.variable_ctx.sub(self)
 
                _escapable = new EscapableClosure(self, variable.closure, null)
@@ -268,6 +274,7 @@ redef class AClosureDecl
 
                old_var_ctx.merge(v.variable_ctx)
                v.variable_ctx = old_var_ctx
+               v.base_variable_ctx = old_base_var_ctx
                v.escapable_ctx.pop
        end
 end
@@ -451,7 +458,7 @@ redef class AIfExpr
                end
 
                # Merge 'then' and 'else' contexts
-               old_var_ctx.merge2(then_var_ctx, v.variable_ctx)
+               old_var_ctx.merge2(then_var_ctx, v.variable_ctx, v.base_variable_ctx)
                v.variable_ctx = old_var_ctx
                _is_typed = true
        end
@@ -466,12 +473,15 @@ redef class AWhileExpr
                _escapable = new EscapableBlock(self)
                v.escapable_ctx.push(_escapable)
                var old_var_ctx = v.variable_ctx
+               var old_base_var_ctx = v.base_variable_ctx
+               v.base_variable_ctx = v.variable_ctx
                v.variable_ctx = v.variable_ctx.sub(self)
 
                super
 
                v.check_conform_expr(n_expr, v.type_bool)
                v.variable_ctx = old_var_ctx
+               v.base_variable_ctx = old_base_var_ctx
                v.escapable_ctx.pop
                _is_typed = true
        end
@@ -491,6 +501,8 @@ redef class AForExpr
                v.escapable_ctx.push(_escapable)
 
                var old_var_ctx = v.variable_ctx
+               var old_base_var_ctx = v.base_variable_ctx
+               v.base_variable_ctx = v.variable_ctx
                v.variable_ctx = v.variable_ctx.sub(self)
                var va = new AutoVariable(n_id.to_symbol, self)
                variable = va
@@ -529,6 +541,7 @@ redef class AForExpr
 
                # pop context
                v.variable_ctx = old_var_ctx
+               v.base_variable_ctx = old_base_var_ctx
                v.escapable_ctx.pop
                _is_typed = true
        end
@@ -559,12 +572,14 @@ redef class AVarAssignExpr
        do
                v.variable_ctx.mark_is_set(variable)
                var t = v.variable_ctx.stype(variable)
-               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
+
+               # Check the base type
+               var btype = v.base_variable_ctx.stype(variable)
+               if not v.check_conform_expr(n_value, btype) then return
+
+               # Bypasse cast if then current type does not match
+               if not n_value.stype < t then v.variable_ctx.stype(variable) = btype
+
                _is_typed = true
        end
 end
@@ -604,12 +619,14 @@ redef class AVarReassignExpr
                var t = v.variable_ctx.stype(variable)
                var t2 = do_rvalue_typing(v, t)
                if t2 == null then return
-               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
+
+               # Check the base type
+               var btype = v.base_variable_ctx.stype(variable)
+               if not v.check_conform(n_value, t2, btype) then return
+
+               # Bypasse cast if then current type does not match
+               if not t2 < t then v.variable_ctx.stype(variable) = btype
+
                _is_typed = true
        end
 end
@@ -1468,6 +1485,8 @@ redef class AClosureDef
                closure = esc.closure
 
                var old_var_ctx = v.variable_ctx
+               var old_base_var_ctx = v.base_variable_ctx
+               v.base_variable_ctx = v.variable_ctx
                v.variable_ctx = v.variable_ctx.sub(self)
                variables = new Array[AutoVariable]
                for i in [0..n_id.length[ do
@@ -1488,6 +1507,7 @@ redef class AClosureDef
                        end
                end
                v.variable_ctx = old_var_ctx
+               v.base_variable_ctx = old_base_var_ctx
        end
 end