rust/src/librustc/middle/effect.rs

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// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Enforces the Rust effect system. Currently there is just one effect,
//! `unsafe`.
use self::UnsafeContext::*;
use middle::def;
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use middle::ty::{self, Ty};
use middle::ty::MethodCall;
use syntax::ast;
use syntax::codemap::Span;
use syntax::visit;
use syntax::visit::Visitor;
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#[derive(Copy, Clone, PartialEq)]
enum UnsafeContext {
SafeContext,
UnsafeFn,
UnsafeBlock(ast::NodeId),
}
fn type_is_unsafe_function(ty: Ty) -> bool {
match ty.sty {
ty::TyBareFn(_, ref f) => f.unsafety == ast::Unsafety::Unsafe,
_ => false,
}
}
struct EffectCheckVisitor<'a, 'tcx: 'a> {
tcx: &'a ty::ctxt<'tcx>,
/// Whether we're in an unsafe context.
unsafe_context: UnsafeContext,
}
impl<'a, 'tcx> EffectCheckVisitor<'a, 'tcx> {
fn require_unsafe(&mut self, span: Span, description: &str) {
match self.unsafe_context {
SafeContext => {
// Report an error.
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span_err!(self.tcx.sess, span, E0133,
"{} requires unsafe function or block",
description);
}
UnsafeBlock(block_id) => {
// OK, but record this.
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debug!("effect: recording unsafe block as used: {}", block_id);
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self.tcx.used_unsafe.borrow_mut().insert(block_id);
}
UnsafeFn => {}
}
}
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fn check_str_index(&mut self, e: &ast::Expr) {
let base_type = match e.node {
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ast::ExprIndex(ref base, _) => ty::node_id_to_type(self.tcx, base.id),
_ => return
};
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debug!("effect: checking index with base type {:?}",
base_type);
match base_type.sty {
ty::TyBox(ty) | ty::TyRef(_, ty::mt{ty, ..}) => if ty::TyStr == ty.sty {
span_err!(self.tcx.sess, e.span, E0134,
"modification of string types is not allowed");
},
ty::TyStr => {
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span_err!(self.tcx.sess, e.span, E0135,
"modification of string types is not allowed");
}
_ => {}
}
}
}
impl<'a, 'tcx, 'v> Visitor<'v> for EffectCheckVisitor<'a, 'tcx> {
fn visit_fn(&mut self, fn_kind: visit::FnKind<'v>, fn_decl: &'v ast::FnDecl,
block: &'v ast::Block, span: Span, _: ast::NodeId) {
let (is_item_fn, is_unsafe_fn) = match fn_kind {
visit::FkItemFn(_, _, unsafety, _, _, _) =>
(true, unsafety == ast::Unsafety::Unsafe),
visit::FkMethod(_, sig, _) =>
(true, sig.unsafety == ast::Unsafety::Unsafe),
_ => (false, false),
};
let old_unsafe_context = self.unsafe_context;
if is_unsafe_fn {
self.unsafe_context = UnsafeFn
} else if is_item_fn {
self.unsafe_context = SafeContext
}
visit::walk_fn(self, fn_kind, fn_decl, block, span);
self.unsafe_context = old_unsafe_context
}
fn visit_block(&mut self, block: &ast::Block) {
let old_unsafe_context = self.unsafe_context;
match block.rules {
ast::DefaultBlock => {}
ast::UnsafeBlock(source) => {
// By default only the outermost `unsafe` block is
// "used" and so nested unsafe blocks are pointless
// (the inner ones are unnecessary and we actually
// warn about them). As such, there are two cases when
// we need to create a new context, when we're
// - outside `unsafe` and found a `unsafe` block
// (normal case)
// - inside `unsafe`, found an `unsafe` block
// created internally to the compiler
//
// The second case is necessary to ensure that the
// compiler `unsafe` blocks don't accidentally "use"
// external blocks (e.g. `unsafe { println("") }`,
// expands to `unsafe { ... unsafe { ... } }` where
// the inner one is compiler generated).
if self.unsafe_context == SafeContext || source == ast::CompilerGenerated {
self.unsafe_context = UnsafeBlock(block.id)
}
}
}
visit::walk_block(self, block);
self.unsafe_context = old_unsafe_context
}
fn visit_expr(&mut self, expr: &ast::Expr) {
match expr.node {
ast::ExprMethodCall(_, _, _) => {
let method_call = MethodCall::expr(expr.id);
let base_type = self.tcx.method_map.borrow().get(&method_call).unwrap().ty;
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debug!("effect: method call case, base type is {:?}",
base_type);
if type_is_unsafe_function(base_type) {
self.require_unsafe(expr.span,
"invocation of unsafe method")
}
}
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ast::ExprCall(ref base, _) => {
let base_type = ty::node_id_to_type(self.tcx, base.id);
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debug!("effect: call case, base type is {:?}",
base_type);
if type_is_unsafe_function(base_type) {
self.require_unsafe(expr.span, "call to unsafe function")
}
}
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ast::ExprUnary(ast::UnDeref, ref base) => {
let base_type = ty::node_id_to_type(self.tcx, base.id);
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debug!("effect: unary case, base type is {:?}",
base_type);
if let ty::TyRawPtr(_) = base_type.sty {
self.require_unsafe(expr.span, "dereference of raw pointer")
}
}
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ast::ExprAssign(ref base, _) | ast::ExprAssignOp(_, ref base, _) => {
self.check_str_index(&**base);
}
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ast::ExprAddrOf(ast::MutMutable, ref base) => {
self.check_str_index(&**base);
}
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ast::ExprInlineAsm(..) => {
self.require_unsafe(expr.span, "use of inline assembly");
}
ast::ExprPath(..) => {
if let def::DefStatic(_, true) = ty::resolve_expr(self.tcx, expr) {
self.require_unsafe(expr.span, "use of mutable static");
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}
}
_ => {}
}
visit::walk_expr(self, expr);
}
}
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pub fn check_crate(tcx: &ty::ctxt) {
let mut visitor = EffectCheckVisitor {
tcx: tcx,
unsafe_context: SafeContext,
};
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visit::walk_crate(&mut visitor, tcx.map.krate());
}