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rustc: Implement let assignability. r=nmatsakis

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This commit is contained in:
Patrick Walton 2012-11-13 14:07:26 -08:00
parent bad62dcb04
commit 3e14ada4f6
2 changed files with 39 additions and 11 deletions
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32
src/librustc/middle/typeck/check.rs
View File

@ -868,6 +868,16 @@ fn check_expr_with(fcx: @fn_ctxt, expr: @ast::expr, expected: ty::t) -> bool {
check_expr(fcx, expr, Some(expected))
}
fn check_expr_with_assignability(fcx: @fn_ctxt,
expr: @ast::expr,
expected: ty::t)
-> bool {
do check_expr_with_unifier(fcx, expr, Some(expected)) {
demand::assign(fcx, expr.span, expected, expr)
}
}
fn check_expr(fcx: @fn_ctxt, expr: @ast::expr,
expected: Option<ty::t>) -> bool {
return do check_expr_with_unifier(fcx, expr, expected) {
@ -1072,11 +1082,7 @@ fn check_expr_with_unifier(fcx: @fn_ctxt,
DontDerefArgs => {}
}
bot |= check_expr_with_unifier(
fcx, *arg, Some(formal_ty),
|| demand::assign(fcx, arg.span,
formal_ty, *arg)
);
bot |= check_expr_with_assignability(fcx, *arg, formal_ty);
fcx.write_ty(arg.id, fcx.expr_ty(*arg));
}
@ -1087,10 +1093,14 @@ fn check_expr_with_unifier(fcx: @fn_ctxt,
}
// A generic function for checking assignment expressions
fn check_assignment(fcx: @fn_ctxt, _sp: span, lhs: @ast::expr,
rhs: @ast::expr, id: ast::node_id) -> bool {
fn check_assignment(fcx: @fn_ctxt,
lhs: @ast::expr,
rhs: @ast::expr,
id: ast::node_id)
-> bool {
let mut bot = check_expr(fcx, lhs, None);
bot |= check_expr_with(fcx, rhs, fcx.expr_ty(lhs));
let lhs_type = fcx.expr_ty(lhs);
bot |= check_expr_with_assignability(fcx, rhs, lhs_type);
fcx.write_ty(id, ty::mk_nil(fcx.ccx.tcx));
return bot;
}
@ -1908,10 +1918,10 @@ fn check_expr_with_unifier(fcx: @fn_ctxt,
};
}
ast::expr_assign(lhs, rhs) => {
bot = check_assignment(fcx, expr.span, lhs, rhs, id);
bot = check_assignment(fcx, lhs, rhs, id);
}
ast::expr_swap(lhs, rhs) => {
bot = check_assignment(fcx, expr.span, lhs, rhs, id);
bot = check_assignment(fcx, lhs, rhs, id);
}
ast::expr_if(cond, thn, elsopt) => {
bot = check_expr_with(fcx, cond, ty::mk_bool(tcx)) |
@ -2246,7 +2256,7 @@ fn require_integral(fcx: @fn_ctxt, sp: span, t: ty::t) {
fn check_decl_initializer(fcx: @fn_ctxt, nid: ast::node_id,
init: @ast::expr) -> bool {
let lty = ty::mk_var(fcx.ccx.tcx, lookup_local(fcx, init.span, nid));
return check_expr_with(fcx, init, lty);
return check_expr_with_assignability(fcx, init, lty);
}
fn check_decl_local(fcx: @fn_ctxt, local: @ast::local) -> bool {

18
src/test/run-pass/let-assignability.rs Normal file
View File

@ -0,0 +1,18 @@
fn f() {
let a = ~"hello";
let b: &str = a;
io::println(b);
}
fn g() {
let c = ~"world";
let d: &str;
d = c;
io::println(d);
}
fn main() {
f();
g();
}