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correct treatment of mutability for deref'd components

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Fixes #2980
This commit is contained in:
Niko Matsakis 2012-07-19 20:13:00 -07:00
parent 1df5c52791
commit 168306f11b
2 changed files with 27 additions and 7 deletions
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25
src/rustc/middle/borrowck/categorization.rs
View File

@ -293,6 +293,18 @@ impl public_methods for borrowck_ctxt {
ret @{cat:cat_discr(cmt, alt_id) with *cmt};
}
/// inherited mutability: used in cases where the mutability of a
/// component is inherited from the base it is a part of. For
/// example, a record field is mutable if it is declared mutable
/// or if the container is mutable.
fn inherited_mutability(base_m: ast::mutability,
comp_m: ast::mutability) -> ast::mutability {
alt comp_m {
m_imm => {base_m} // imm: as mutable as the container
m_mutbl | m_const => {comp_m}
}
}
fn cat_field<N:ast_node>(node: N, base_cmt: cmt,
f_name: ast::ident) -> cmt {
let f_mutbl = alt field_mutbl(self.tcx, base_cmt.ty, f_name) {
@ -304,10 +316,7 @@ impl public_methods for borrowck_ctxt {
*f_name, ty_to_str(self.tcx, base_cmt.ty)]);
}
};
let m = alt f_mutbl {
m_imm { base_cmt.mutbl } // imm: as mutable as the container
m_mutbl | m_const { f_mutbl }
};
let m = self.inherited_mutability(base_cmt.mutbl, f_mutbl);
let f_comp = comp_field(f_name, f_mutbl);
let lp = base_cmt.lp.map(|lp| @lp_comp(lp, f_comp) );
@{id: node.id(), span: node.span(),
@ -327,10 +336,11 @@ impl public_methods for borrowck_ctxt {
// Other ptr types admit aliases and are therefore
// not loanable.
alt ptr {
uniq_ptr {some(@lp_deref(l, ptr))}
gc_ptr | region_ptr | unsafe_ptr {none}
uniq_ptr => {some(@lp_deref(l, ptr))}
gc_ptr | region_ptr | unsafe_ptr => {none}
}
};
@{id:node.id(), span:node.span(),
cat:cat_deref(base_cmt, derefs, ptr), lp:lp,
mutbl:mt.mutbl, ty:mt.ty}
@ -338,9 +348,10 @@ impl public_methods for borrowck_ctxt {
deref_comp(comp) {
let lp = base_cmt.lp.map(|l| @lp_comp(l, comp) );
let m = self.inherited_mutability(base_cmt.mutbl, mt.mutbl);
@{id:node.id(), span:node.span(),
cat:cat_comp(base_cmt, comp), lp:lp,
mutbl:mt.mutbl, ty:mt.ty}
mutbl:m, ty:mt.ty}
}
}
}

9
src/test/compile-fail/borrowck-mut-deref-comp.rs Normal file
View File

@ -0,0 +1,9 @@
enum foo = ~int;
fn borrow(x: @mut foo) {
let y = &***x; //~ ERROR illegal borrow unless pure: unique value in aliasable, mutable location
*x = foo(~4); //~ NOTE impure due to assigning to dereference of mutable @ pointer
}
fn main() {
}