syntax: fix OR if_false_var_ctx passing.
[nit.git] / src / syntax / typing.nit
index d3a196a..421b433 100644 (file)
@@ -19,6 +19,7 @@ package typing
 
 import syntax_base
 import escape
+import control_flow
 
 redef class MMSrcModule
        # Walk trough the module and type statments and expressions
@@ -45,6 +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)
 
@@ -64,11 +68,19 @@ special AbsSyntaxVisitor
        private meth use_if_true_variable_ctx(e: PExpr)
        do
                var ctx = e.if_true_variable_ctx
-               if ctx != null then
-                       variable_ctx = ctx
-               end
+               if ctx != null then variable_ctx = ctx
+       end
+
+       # Make the if_false_variable_ctx of the expression effective
+       private meth use_if_false_variable_ctx(e: PExpr)
+       do
+               var ctx = e.if_false_variable_ctx
+               if ctx != null then variable_ctx = ctx
        end
 
+       # Number of nested once
+       readable writable attr _once_count: Int = 0
+
        init(tc, module) do super
 
        private meth get_default_constructor_for(n: PNode, c: MMLocalClass, prop: MMSrcMethod): MMMethod
@@ -121,100 +133,6 @@ special AbsSyntaxVisitor
        end
 end
 
-# Associate symbols to variable and variables to type
-# Can be nested
-private class VariableContext
-       # Look for the variable from its name
-       # Return null if nothing found
-       meth [](s: Symbol): Variable
-       do
-               if _dico.has_key(s) then
-                       return _dico[s]
-               else
-                       return null
-               end
-       end
-
-       # Register a new variable with its name
-       meth add(v: Variable)
-       do
-               _dico[v.name] = v
-       end
-
-
-       # The effective static type of a given variable
-       # May be different from the declaration static type
-       meth stype(v: Variable): MMType
-       do
-               return v.stype
-       end
-
-       # Variables by name (in the current context only)
-       attr _dico: Map[Symbol, Variable]
-
-       # Build a new VariableContext
-       meth sub: SubVariableContext
-       do
-               return new SubVariableContext.with_prev(self)
-       end
-
-       # Build a nested VariableContext with new variable information
-       meth sub_with(v: Variable, t: MMType): SubVariableContext
-       do
-               return new CastVariableContext.with_prev(self, v, t)
-       end
-
-       init
-       do 
-               _dico = new HashMap[Symbol, Variable]
-       end
-end
-
-private class SubVariableContext
-special VariableContext
-       readable attr _prev: VariableContext
-
-       redef meth [](s)
-       do
-               if _dico.has_key(s) then
-                       return _dico[s]
-               else
-                       return prev[s]
-               end
-       end
-
-       redef meth stype(v)
-       do
-               return prev.stype(v)
-       end
-
-       init with_prev(p: VariableContext)
-       do
-               init
-               _prev = p
-       end
-end
-
-private class CastVariableContext
-special SubVariableContext
-       attr _variable: Variable
-       attr _var_type: MMType
-
-       redef meth stype(v)
-       do
-               if _variable == v then
-                       return _var_type
-               end
-               return prev.stype(v)
-       end
-
-       init with_prev(p: VariableContext, v: Variable, t: MMType)
-       do
-               super(p)
-               _variable = v
-               _var_type =t
-       end
-end
 
 ###############################################################################
 
@@ -250,12 +168,23 @@ redef class AMethPropdef
        redef readable attr _self_var: ParamVariable
        redef meth accept_typing(v)
        do
-               v.variable_ctx = new VariableContext
+               v.variable_ctx = new RootVariableContext(v, self)
+               v.base_variable_ctx = v.variable_ctx
                _self_var = v.self_var
                super
        end
 end
 
+redef class AConcreteMethPropdef
+       redef meth accept_typing(v)
+       do
+               super
+               if v.variable_ctx.unreash == false and method.signature.return_type != null then
+                       v.error(self, "Control error: Reached end of function (a 'return' with a value was expected).")
+               end
+       end
+end
+
 redef class AConcreteInitPropdef
        readable attr _super_init_calls: Array[MMMethod] = new Array[MMMethod]
        readable attr _explicit_super_init_calls: Array[MMMethod] = new Array[MMMethod]
@@ -324,14 +253,28 @@ redef class AClosureDecl
                v.variable_ctx.add(variable)
 
                var old_var_ctx = v.variable_ctx
-               v.variable_ctx = v.variable_ctx.sub
+               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)
                v.escapable_ctx.push(_escapable)
 
                super
 
+               if n_expr != null then
+                       if v.variable_ctx.unreash == false then
+                               if variable.closure.signature.return_type != null then
+                                       v.error(self, "Control error: Reached end of block (a 'continue' with a value was expected).")
+                               else if variable.closure.is_break then
+                                       v.error(self, "Control error: Reached end of break block (an 'abort' was expected).")
+                               end
+                       end
+               end
+
+               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
@@ -345,8 +288,22 @@ redef class PType
 end
 
 redef class PExpr
-       redef readable attr _stype: MMType
-       
+       redef readable attr _is_typed: Bool = false
+       redef meth is_statement: Bool do return _stype == null
+       redef meth stype
+       do
+               if not is_typed then
+                       print "{locate}: not is_typed"
+                       abort
+               end
+               if is_statement then
+                       print "{locate}: is_statement"
+                       abort
+               end
+               return _stype
+       end
+       attr _stype: MMType
+
        # Is the expression the implicit receiver
        meth is_implicit_self: Bool do return false
 
@@ -358,6 +315,9 @@ redef class PExpr
 
        # The variable type information if current boolean expression is true
        readable private attr _if_true_variable_ctx: VariableContext
+
+       # The variable type information if current boolean expression is false
+       readable private attr _if_false_variable_ctx: VariableContext
 end
 
 redef class AVardeclExpr
@@ -366,6 +326,7 @@ redef class AVardeclExpr
                var va = new VarVariable(n_id.to_symbol, self)
                variable = va
                v.variable_ctx.add(va)
+               if n_expr != null then v.variable_ctx.mark_is_set(va)
 
                if n_type != null then
                        va.stype = n_type.stype
@@ -373,9 +334,10 @@ redef class AVardeclExpr
                                v.check_conform_expr(n_expr, va.stype)
                        end
                else
-                       v.check_expr(n_expr)
+                       if not v.check_expr(n_expr) then return
                        va.stype = n_expr.stype
                end
+               _is_typed = true
        end
 end
 
@@ -383,17 +345,26 @@ redef class ABlockExpr
        redef meth accept_typing(v)
        do
                var old_var_ctx = v.variable_ctx
-               v.variable_ctx = v.variable_ctx.sub
+               v.variable_ctx = v.variable_ctx.sub(self)
 
-               super
+               for e in n_expr do
+                       if v.variable_ctx.unreash and not v.variable_ctx.already_unreash then
+                               v.variable_ctx.already_unreash = true
+                               v.warning(e, "Warning: unreachable statement.")
+                       end
+                       v.visit(e)
+               end
 
+               old_var_ctx.merge(v.variable_ctx)
                v.variable_ctx = old_var_ctx
+               _is_typed = true
        end
 end
 
 redef class AReturnExpr
        redef meth after_typing(v)
        do
+               v.variable_ctx.unreash = true
                var t = v.local_property.signature.return_type
                if n_expr == null and t != null then
                        v.error(self, "Error: Return without value in a function.")
@@ -402,12 +373,14 @@ redef class AReturnExpr
                else if n_expr != null and t != null then
                        v.check_conform_expr(n_expr, t)
                end
+               _is_typed = true
        end
 end
 
 redef class AContinueExpr
        redef meth after_typing(v)
        do
+               v.variable_ctx.unreash = true
                var esc = compute_escapable_block(v.escapable_ctx)
                if esc == null then return
 
@@ -424,12 +397,14 @@ redef class AContinueExpr
                else if n_expr != null and t != null then
                        v.check_conform_expr(n_expr, t)
                end
+               _is_typed = true
        end
 end
 
 redef class ABreakExpr
        redef meth after_typing(v)
        do
+               v.variable_ctx.unreash = true
                var esc = compute_escapable_block(v.escapable_ctx)
                if esc == null then return
 
@@ -442,6 +417,14 @@ redef class ABreakExpr
                        # Typing check can only be done later
                        bl.add(n_expr)
                end
+               _is_typed = true
+       end
+end
+
+redef class AAbortExpr
+       redef meth after_typing(v)
+       do
+               v.variable_ctx.unreash = true
        end
 end
 
@@ -452,16 +435,32 @@ redef class AIfExpr
                v.visit(n_expr)
                v.check_conform_expr(n_expr, v.type_bool)
 
+               # Prepare 'then' context
                v.use_if_true_variable_ctx(n_expr)
 
-               v.visit(n_then)
-               # Restore variable ctx
+               # Process the 'then'
+               if n_then != null then
+                       v.variable_ctx = v.variable_ctx.sub(n_then)
+                       v.visit(n_then)
+               end
+
+               # Remember what appened in the 'then'
+               var then_var_ctx = v.variable_ctx
+
+               # Prepare 'else' context
                v.variable_ctx = old_var_ctx
+               v.use_if_false_variable_ctx(n_expr)
 
+               # Process the 'else'
                if n_else != null then
+                       v.variable_ctx = v.variable_ctx.sub(n_else)
                        v.visit(n_else)
-                       v.variable_ctx = old_var_ctx
                end
+
+               # Merge 'then' and 'else' contexts
+               old_var_ctx.merge2(then_var_ctx, v.variable_ctx, v.base_variable_ctx)
+               v.variable_ctx = old_var_ctx
+               _is_typed = true
        end
 end
 
@@ -473,11 +472,28 @@ redef class AWhileExpr
        do
                _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
-
+               # Process condition
+               v.visit(n_expr)
                v.check_conform_expr(n_expr, v.type_bool)
+
+               # Prepare inside context (assert cond)
+               v.use_if_true_variable_ctx(n_expr)
+
+               # Process inside
+               if n_block != null then
+                       v.variable_ctx = v.variable_ctx.sub(n_block)
+                       v.visit(n_block)
+               end
+
+               v.variable_ctx = old_var_ctx
+               v.base_variable_ctx = old_base_var_ctx
                v.escapable_ctx.pop
+               _is_typed = true
        end
 end
 
@@ -494,17 +510,18 @@ redef class AForExpr
                _escapable = new EscapableBlock(self)
                v.escapable_ctx.push(_escapable)
 
-               v.variable_ctx = v.variable_ctx.sub
+               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
                v.variable_ctx.add(va)
 
                v.visit(n_expr)
 
+               if not v.check_conform_expr(n_expr, v.type_collection) then return
                var expr_type = n_expr.stype
-               if not v.check_conform_expr(n_expr, v.type_collection) then
-                       return
-               end
                _meth_iterator = expr_type.local_class.select_method(once ("iterator".to_symbol))
                if _meth_iterator == null then
                        v.error(self, "Error: Collection MUST have an iterate method")
@@ -533,11 +550,10 @@ redef class AForExpr
                if n_block != null then v.visit(n_block)
 
                # pop context
-               var varctx = v.variable_ctx 
-               assert varctx isa SubVariableContext
-               v.variable_ctx = varctx.prev
-
+               v.variable_ctx = old_var_ctx
+               v.base_variable_ctx = old_base_var_ctx
                v.escapable_ctx.pop
+               _is_typed = true
        end
 end
 
@@ -546,6 +562,7 @@ redef class AAssertExpr
        do
                v.check_conform_expr(n_expr, v.type_bool)
                v.use_if_true_variable_ctx(n_expr)
+               _is_typed = true
        end
 end
 
@@ -554,37 +571,50 @@ redef class AVarExpr
 
        redef meth after_typing(v)
        do
+               v.variable_ctx.check_is_set(self, variable)
                _stype = v.variable_ctx.stype(variable)
+               _is_typed = _stype != null
        end
 end
 
 redef class AVarAssignExpr
        redef meth after_typing(v)
        do
+               v.variable_ctx.mark_is_set(variable)
                var t = v.variable_ctx.stype(variable)
-               v.check_conform_expr(n_value, t)
+
+               # Check the base type
+               var btype = v.base_variable_ctx.stype(variable)
+               if not v.check_conform_expr(n_value, btype) then return
+
+               # Always cast
+               v.variable_ctx.stype(variable) = n_value.stype
+
+               _is_typed = true
        end
 end
 
 redef class AReassignFormExpr
-       # Compute and check method used through the reassigment operator 
-       private meth do_lvalue_typing(v: TypingVisitor, type_lvalue: MMType)
+       # Compute and check method used through the reassigment operator
+       # On success return the static type of the result of the reassigment operator
+       # Else display an error and return null
+       private meth do_rvalue_typing(v: TypingVisitor, type_lvalue: MMType): MMType
        do
                if type_lvalue == null then
-                       return
+                       return null
                end
                var name = n_assign_op.method_name
                var lc = type_lvalue.local_class
                if not lc.has_global_property_by_name(name) then
                        v.error(self, "Error: Method '{name}' doesn't exists in {type_lvalue}.")
-                       return
+                       return null
                end
                var prop = lc.select_method(name)
                prop.global.check_visibility(v, self, v.module, false)
                var psig = prop.signature_for(type_lvalue)
                _assign_method = prop
-               v.check_conform_expr(n_value, psig[0].not_for_self)
-               v.check_conform(self, psig.return_type.not_for_self, n_value.stype)
+               if not v.check_conform_expr(n_value, psig[0].not_for_self) then return null
+               return psig.return_type.not_for_self
        end
 
        # Method used through the reassigment operator (once computed)
@@ -594,8 +624,20 @@ end
 redef class AVarReassignExpr
        redef meth after_typing(v)
        do
+               v.variable_ctx.check_is_set(self, variable)
+               v.variable_ctx.mark_is_set(variable)
                var t = v.variable_ctx.stype(variable)
-               do_lvalue_typing(v, t)
+               var t2 = do_rvalue_typing(v, t)
+               if t2 == null then return
+
+               # Check the base type
+               var btype = v.base_variable_ctx.stype(variable)
+               if not v.check_conform(n_value, t2, btype) then return
+
+               # Always cast
+               v.variable_ctx.stype(variable) = t2
+
+               _is_typed = true
        end
 end
 
@@ -616,6 +658,7 @@ redef class ASelfExpr
        do
                variable = v.self_var
                _stype = v.variable_ctx.stype(variable)
+               _is_typed = true
        end
 
         redef meth is_self do return true
@@ -634,11 +677,13 @@ redef class AIfexprExpr
                v.use_if_true_variable_ctx(n_expr)
                v.visit(n_then)
                v.variable_ctx = old_var_ctx
+               v.use_if_false_variable_ctx(n_expr)
                v.visit(n_else)
 
                v.check_conform_expr(n_expr, v.type_bool)
 
                _stype = v.check_conform_multiexpr(null, [n_then, n_else])
+               _is_typed = _stype != null
        end
 end
 
@@ -646,15 +691,31 @@ redef class ABoolExpr
        redef meth after_typing(v)
        do
                _stype = v.type_bool
+               _is_typed = true
        end
 end
 
 redef class AOrExpr
-       redef meth after_typing(v)
+       redef meth accept_typing(v)
        do
+               var old_var_ctx = v.variable_ctx
+
+               v.visit(n_expr)
+               v.use_if_false_variable_ctx(n_expr)
+
+               v.visit(n_expr2)
+               if n_expr2.if_false_variable_ctx != null then 
+                       _if_false_variable_ctx = n_expr2.if_false_variable_ctx
+               else
+                       _if_false_variable_ctx = v.variable_ctx
+               end
+
+               v.variable_ctx = old_var_ctx
+
                v.check_conform_expr(n_expr, v.type_bool)
                v.check_conform_expr(n_expr2, v.type_bool)
                _stype = v.type_bool
+               _is_typed = true
        end
 end
 
@@ -678,6 +739,7 @@ redef class AAndExpr
                v.check_conform_expr(n_expr, v.type_bool)
                v.check_conform_expr(n_expr2, v.type_bool)
                _stype = v.type_bool
+               _is_typed = true
        end
 end
 
@@ -685,7 +747,13 @@ redef class ANotExpr
        redef meth after_typing(v)
        do
                v.check_conform_expr(n_expr, v.type_bool)
+
+               # Invert if_true/if_false information
+               _if_false_variable_ctx = n_expr._if_true_variable_ctx
+               _if_true_variable_ctx = n_expr._if_false_variable_ctx
+
                _stype = v.type_bool
+               _is_typed = true
        end
 end
 
@@ -693,7 +761,7 @@ redef class AIntExpr
        redef meth after_typing(v)
        do
                _stype = v.type_int
-
+               _is_typed = true
        end
 end
 
@@ -701,6 +769,7 @@ redef class AFloatExpr
        redef meth after_typing(v)
        do
                _stype = v.type_float
+               _is_typed = true
        end
 end
 
@@ -708,6 +777,7 @@ redef class ACharExpr
        redef meth after_typing(v)
        do
                _stype = v.type_char
+               _is_typed = true
        end
 end
 
@@ -716,6 +786,7 @@ redef class AStringFormExpr
        redef meth after_typing(v)
        do
                _stype = v.type_string
+               _is_typed = true
                _meth_with_native = _stype.local_class.select_method(once "with_native".to_symbol)
                if _meth_with_native == null then v.error(self, "{_stype} MUST have a with_native method.")
        end
@@ -736,6 +807,7 @@ redef class ASuperstringExpr
                if _meth_add == null then v.error(self, "{_atype} MUST have an add method.")
                _meth_to_s = v.type_object.local_class.select_method(once "to_s".to_symbol)
                if _meth_to_s == null then v.error(self, "Object MUST have a to_s method.")
+               _is_typed = true
        end
 end
 
@@ -743,6 +815,7 @@ redef class ANullExpr
        redef meth after_typing(v)
        do
                _stype = v.type_none
+               _is_typed = true
        end
 end
 
@@ -765,6 +838,8 @@ redef class AArrayExpr
                if _meth_with_capacity == null then v.error(self, "{_stype} MUST have a with_capacity method.")
                _meth_add = _stype.local_class.select_method(once "add".to_symbol)
                if _meth_add == null then v.error(self, "{_stype} MUST have an add method.")
+
+               _is_typed = true
        end
 end
 
@@ -772,11 +847,9 @@ redef class ARangeExpr
        readable attr _meth_init: MMMethod
        redef meth after_typing(v)
        do
+               if not v.check_expr(n_expr) or not v.check_expr(n_expr2) then return
                var ntype = n_expr.stype
                var ntype2 = n_expr2.stype
-               if ntype == null or ntype == null then
-                       return
-               end
                if ntype < ntype2 then
                        ntype = ntype2
                else if not ntype2 < ntype then
@@ -784,9 +857,9 @@ redef class ARangeExpr
                        return
                end
                var dtype = v.type_discrete
-               v.check_conform_expr(n_expr, dtype)
-               v.check_conform_expr(n_expr2, dtype)
+               if not v.check_conform_expr(n_expr, dtype) or not v.check_conform_expr(n_expr2, dtype) then return
                _stype = v.type_range(ntype)
+               _is_typed = true
        end
 end
 
@@ -863,6 +936,7 @@ special ASuperInitCall
                var p = v.local_property
                assert p isa MMSrcMethod
                _prop = p
+               _is_typed = true
        end
 end
 
@@ -899,10 +973,9 @@ redef class AAttrExpr
        redef meth after_typing(v)
        do
                do_typing(v)
-               if prop == null then
-                       return
-               end
+               if prop == null then return
                _stype = attr_type
+               _is_typed = true
        end
 end
 
@@ -910,10 +983,9 @@ redef class AAttrAssignExpr
        redef meth after_typing(v)
        do
                do_typing(v)
-               if prop == null then
-                       return
-               end
-               v.check_conform_expr(n_value, attr_type)
+               if prop == null then return
+               if not v.check_conform_expr(n_value, attr_type) then return
+               _is_typed = true
        end
 end
 
@@ -921,10 +993,11 @@ redef class AAttrReassignExpr
        redef meth after_typing(v)
        do
                do_typing(v)
-               if prop == null then
-                       return
-               end
-               do_lvalue_typing(v, attr_type)
+               if prop == null then return
+               var t = do_rvalue_typing(v, attr_type)
+               if t == null then return
+               v.check_conform(self, t, n_value.stype)
+               _is_typed = true
        end
 end
 
@@ -1026,6 +1099,7 @@ special AAbsAbsSendExpr
                var args = process_signature(v, sig, prop.name, raw_args)
                if args == null then return
                var rtype = process_closures(v, sig, prop.name, closure_defs)
+               if rtype == null and sig.return_type != null then return
                _prop = prop
                _prop_signature = sig
                _arguments = args
@@ -1138,8 +1212,10 @@ special AAbsSendExpr
 
                if not prop.global.is_init then
                        v.error(self, "Error: {prop} is not a constructor.")
+                       return
                end
                _stype = t
+               _is_typed = true
        end
 end
 
@@ -1177,6 +1253,7 @@ special ASuperInitCall
                end
 
                _stype = return_type
+               _is_typed = true
        end
 end
 
@@ -1200,7 +1277,9 @@ special AReassignFormExpr
                var t = prop.signature_for(n_expr.stype).return_type
                if not n_expr.is_self then t = t.not_for_self
 
-               do_lvalue_typing(v, t)
+               var t2 = do_rvalue_typing(v, t)
+               if t2 == null then return
+               v.check_conform(self, t2, n_value.stype)
 
                _read_prop = prop
                var old_args = arguments
@@ -1217,6 +1296,7 @@ special AReassignFormExpr
                end
 
                _arguments = old_args # FIXME: What if star parameters do not match betwen the two methods?
+               _is_typed = true
        end
 end
 
@@ -1273,7 +1353,7 @@ redef class ACallFormExpr
                        var variable = v.variable_ctx[name]
                        if variable != null then
                                if variable isa ClosureVariable then
-                                       var n = new AClosureCallExpr(n_id, n_args, n_closure_defs)
+                                       var n = new AClosureCallExpr.init_aclosurecallexpr(n_id, n_args, n_closure_defs)
                                        replace_with(n)
                                        n.variable = variable
                                        n.after_typing(v)
@@ -1281,6 +1361,7 @@ redef class ACallFormExpr
                                else
                                        if not n_args.is_empty then
                                                v.error(self, "Error: {name} is variable, not a function.")
+                                               return
                                        end
                                        var vform = variable_create(variable)
                                        vform.variable = variable
@@ -1368,19 +1449,21 @@ redef class AInitExpr
 end
 
 redef class AClosureCallExpr
+special AAbsAbsSendExpr
        redef meth after_typing(v)
        do
                var va = variable
+               if va.closure.is_break then v.variable_ctx.unreash = true
                var sig = va.closure.signature
                var args = process_signature(v, sig, n_id.to_symbol, n_args.to_a)
-               if closure_defs != null then
-                       process_closures(v, sig, n_id.to_symbol, closure_defs)
+               if not n_closure_defs.is_empty then
+                       process_closures(v, sig, n_id.to_symbol, n_closure_defs.to_a)
                end
                if args == null then return
-               _prop = null
                _prop_signature = sig
                _arguments = args
                _stype = sig.return_type
+               _is_typed = true
        end
 end
 
@@ -1411,7 +1494,10 @@ redef class AClosureDef
 
                closure = esc.closure
 
-               v.variable_ctx = v.variable_ctx.sub
+               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
                        var va = new AutoVariable(n_id[i].to_symbol, self)
@@ -1422,31 +1508,79 @@ redef class AClosureDef
 
                _accept_typing2 = true
                accept_typing(v)
+
+               if v.variable_ctx.unreash == false then
+                       if closure.signature.return_type != null then
+                               v.error(self, "Control error: Reached end of block (a 'continue' with a value was expected).")
+                       else if closure.is_break then
+                               v.error(self, "Control error: Reached end of break block (a 'break' was expected).")
+                       end
+               end
+               v.variable_ctx = old_var_ctx
+               v.base_variable_ctx = old_base_var_ctx
+       end
+end
+
+class ATypeCheckExpr
+special PExpr
+       private meth check_expr_cast(v: TypingVisitor, n_expr: PExpr, n_type: PType)
+       do
+               if not v.check_expr(n_expr) then return
+               var etype = n_expr.stype
+               var ttype = n_type.stype
+               if etype == ttype then
+                       v.warning(self, "Warning: Expression is already a {ttype}.")
+               else if etype < ttype then
+                       v.warning(self, "Warning: Expression is already a {ttype} since it is a {etype}.")
+               end
        end
 end
 
 redef class AIsaExpr
+special ATypeCheckExpr
        redef meth after_typing(v)
        do
+               check_expr_cast(v, n_expr, n_type)
                var variable = n_expr.its_variable
                if variable != null then
-                       _if_true_variable_ctx = v.variable_ctx.sub_with(variable, n_type.stype)
+                       _if_true_variable_ctx = v.variable_ctx.sub_with(self, variable, n_type.stype)
                end
                _stype = v.type_bool
+               _is_typed = true
        end
 end
 
 redef class AAsCastExpr
+special ATypeCheckExpr
        redef meth after_typing(v)
        do
-               v.check_expr(n_expr)
+               check_expr_cast(v, n_expr, n_type)
                _stype = n_type.stype
+               _is_typed = _stype != null
        end
 end
 
 redef class AProxyExpr
        redef meth after_typing(v)
        do
+               if not n_expr.is_typed then return
+               _is_typed = true
+               if n_expr.is_statement then return
                _stype = n_expr.stype
        end
 end
+
+redef class AOnceExpr
+       redef meth accept_typing(v)
+       do
+               if v.once_count > 0 then
+                       v.warning(self, "Useless once in a once expression.")
+               end
+               v.once_count = v.once_count + 1
+
+               super
+
+               v.once_count = v.once_count - 1
+       end
+end
+