+++ /dev/null
-# This file is part of NIT ( http://www.nitlanguage.org ).
-#
-# Copyright 2008 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.
-
-# Analysis control flow in property bodies, statements and expressions
-package control_flow
-
-import syntax_base
-
-redef class MMSrcModule
- # Walk trough the module and type statments and expressions
- # Require than supermodules are processed
- meth do_control_flow(tc: ToolContext)
- do
- var tv = new ControlFlowVisitor(tc, self)
- tv.visit(node)
- end
-end
-
-redef class Variable
- # Is the variable must be set before being used ?
- meth must_be_set: Bool do return false
-end
-
-redef class VarVariable
- redef meth must_be_set do return true
-end
-
-
-
-# Control flow visitor
-# * Check reachability in methods
-# * Associate breaks and continues
-# * Check some other warning
-private class ControlFlowVisitor
-special AbsSyntaxVisitor
- redef meth visit(n)
- do
- if n != null then n.accept_control_flow(self)
- end
-
- # Number of nested once
- readable writable attr _once_count: Int = 0
-
- # Current knowledge about variables types
- readable writable attr _control_flow_ctx: ControlFlowContext
-
- meth check_is_set(n: PNode, v: Variable)
- do
- if v.must_be_set and not control_flow_ctx.is_set(v) then
- error(n, "Error: variable '{v}' is possibly unset.")
- var cfc = control_flow_ctx
- while cfc != null do
- print("cfc: " + cfc.set_variables.join(" "))
- cfc = cfc.prev
- end
- end
- end
-
- meth mark_is_set(v: Variable)
- do
- control_flow_ctx.set_variables.add(v)
- end
-
- init(tc, m) do super
-end
-
-private class ControlFlowContext
- # Previous control flow context if any
- readable attr _prev: ControlFlowContext
-
- # Is a control flow break met? (return, break, continue)
- readable writable attr _unreash: Bool = false
-
- # Is a control flow already broken?
- # Used to avoid repeating the same error message
- readable writable attr _already_unreash: Bool = false
-
- # Set of variable that are set (assigned)
- readable attr _set_variables: HashSet[Variable] = new HashSet[Variable]
-
- # Is a variable set?
- meth is_set(v: Variable): Bool
- do
- return _set_variables.has(v) or (_prev != null and _prev.is_set(v))
- end
-
- meth sub: ControlFlowContext
- do
- return new ControlFlowContext.with_prev(self)
- end
-
- init
- do
- end
-
- init with_prev(p: ControlFlowContext)
- do
- _prev = p
- _unreash = p.unreash
- _already_unreash = p.already_unreash
- end
-end
-
-###############################################################################
-
-redef class PNode
- private meth accept_control_flow(v: ControlFlowVisitor)
- do
- accept_abs_syntax_visitor(v)
- end
-end
-
-redef class AMethPropdef
- redef meth accept_control_flow(v)
- do
- v.control_flow_ctx = new ControlFlowContext
- super
- end
-end
-
-redef class AConcreteMethPropdef
- redef meth accept_control_flow(v)
- do
- super
- if v.control_flow_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 AVardeclExpr
- redef meth accept_control_flow(v)
- do
- super
- if n_expr != null then v.mark_is_set(variable)
- end
-end
-
-redef class ABlockExpr
- redef meth accept_control_flow(v)
- do
- for e in n_expr do
- if v.control_flow_ctx.unreash and not v.control_flow_ctx.already_unreash then
- v.control_flow_ctx.already_unreash = true
- v.warning(e, "Warning: unreachable statement.")
- end
- v.visit(e)
- end
- end
-end
-
-redef class AReturnExpr
- redef meth accept_control_flow(v)
- do
- super
- v.control_flow_ctx.unreash = true
- end
-end
-
-redef class ABreakExpr
- redef meth accept_control_flow(v)
- do
- super
- v.control_flow_ctx.unreash = true
- end
-end
-redef class AContinueExpr
- redef meth accept_control_flow(v)
- do
- super
- v.control_flow_ctx.unreash = true
- end
-end
-
-redef class AAbortExpr
- redef meth accept_control_flow(v)
- do
- super
- v.control_flow_ctx.unreash = true
- end
-end
-
-redef class AClosureCallExpr
- redef meth accept_control_flow(v)
- do
- super
- if variable.closure.is_break then v.control_flow_ctx.unreash = true
- end
-end
-
-redef class AIfExpr
- redef meth accept_control_flow(v)
- do
- v.visit(n_expr)
-
- var old_control_flow_ctx = v.control_flow_ctx
- v.control_flow_ctx = v.control_flow_ctx.sub
-
- v.visit(n_then)
-
- if n_else == null then
- # Restore control flow ctx since the 'then" block is optional
- v.control_flow_ctx = old_control_flow_ctx
- else
- # Remember what appens in the 'then'
- var then_control_flow_ctx = v.control_flow_ctx
- # Reset to execute the 'else'
- v.control_flow_ctx = old_control_flow_ctx.sub
-
- v.visit(n_else)
-
- # Merge then and else in the old control_flow
- old_control_flow_ctx.unreash = v.control_flow_ctx.unreash and then_control_flow_ctx.unreash
-
- if v.control_flow_ctx.unreash then v.control_flow_ctx = then_control_flow_ctx
- if then_control_flow_ctx.unreash then then_control_flow_ctx = v.control_flow_ctx
- for variable in v.control_flow_ctx.set_variables do
- if then_control_flow_ctx.is_set(variable) then
- old_control_flow_ctx.set_variables.add(variable)
- end
- end
- v.control_flow_ctx = old_control_flow_ctx
- end
- end
-end
-
-class AControlableBlock
-special PExpr
- redef meth accept_control_flow(v)
- do
- # Store old control flow values
- var old_control_flow_ctx = v.control_flow_ctx
- v.control_flow_ctx = v.control_flow_ctx.sub
-
- super
-
- # Check control flow if any
- check_control_flow(v)
-
- # Restore control flow value since all controlable blocks are optionnal
- v.control_flow_ctx = old_control_flow_ctx
- end
-
- private meth check_control_flow(v: ControlFlowVisitor) do end
-end
-
-redef class AWhileExpr
-special AControlableBlock
-end
-
-redef class AForExpr
-special AControlableBlock
-end
-
-redef class AVarExpr
- redef meth accept_control_flow(v)
- do
- super
- v.check_is_set(self, variable)
- end
-end
-
-redef class AVarAssignExpr
- redef meth accept_control_flow(v)
- do
- super
- v.mark_is_set(variable)
- end
-end
-
-redef class AVarReassignExpr
- redef meth accept_control_flow(v)
- do
- super
- v.check_is_set(self, variable)
- v.mark_is_set(variable)
- end
-end
-
-redef class AClosureDecl
- redef meth accept_control_flow(v)
- do
- if n_expr != null then
- var old_control_flow_ctx = v.control_flow_ctx
- v.control_flow_ctx = v.control_flow_ctx.sub
-
- super
-
- if v.control_flow_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
-
- v.control_flow_ctx = old_control_flow_ctx
- end
- end
-end
-
-redef class AClosureDef
-special AControlableBlock
- redef meth accept_control_flow(v)
- do
- for va in variables do v.mark_is_set(va)
- super
- end
-
- redef meth check_control_flow(v)
- do
- if v.control_flow_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
- end
-end
-
-redef class AOnceExpr
- redef meth accept_control_flow(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
-
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