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derive: emit intrinsics::unreachable for impls on empty enums

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fixes #31574
This commit is contained in:
Alex Burka 2016-03-03 11:45:58 -05:00
parent c433b703ea
commit a09a41928f
1 changed files with 18 additions and 11 deletions
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29
src/libsyntax_ext/deriving/generic/mod.rs
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@ -381,6 +381,22 @@ fn find_type_parameters(ty: &ast::Ty, ty_param_names: &[ast::Name]) -> Vec<P<ast
visitor.types
}
/// Replacement for expr_unreachable which generates intrinsics::unreachable()
/// instead of unreachable!()
fn expr_unreachable_intrinsic(cx: &ExtCtxt, sp: Span) -> P<Expr> {
let path = cx.std_path(&["intrinsics", "unreachable"]);
let call = cx.expr_call_global(
sp, path, vec![]);
let unreachable = cx.expr_block(P(ast::Block {
stmts: vec![],
expr: Some(call),
id: ast::DUMMY_NODE_ID,
rules: ast::BlockCheckMode::Unsafe(ast::CompilerGenerated),
span: sp }));
unreachable
}
impl<'a> TraitDef<'a> {
pub fn expand(&self,
cx: &mut ExtCtxt,
@ -1297,16 +1313,7 @@ impl<'a> MethodDef<'a> {
//Since we know that all the arguments will match if we reach the match expression we
//add the unreachable intrinsics as the result of the catch all which should help llvm
//in optimizing it
let path = cx.std_path(&["intrinsics", "unreachable"]);
let call = cx.expr_call_global(
sp, path, vec![]);
let unreachable = cx.expr_block(P(ast::Block {
stmts: vec![],
expr: Some(call),
id: ast::DUMMY_NODE_ID,
rules: ast::BlockCheckMode::Unsafe(ast::CompilerGenerated),
span: sp }));
match_arms.push(cx.arm(sp, vec![cx.pat_wild(sp)], unreachable));
match_arms.push(cx.arm(sp, vec![cx.pat_wild(sp)], expr_unreachable_intrinsic(cx, sp)));
// Final wrinkle: the self_args are expressions that deref
// down to desired l-values, but we cannot actually deref
@ -1382,7 +1389,7 @@ impl<'a> MethodDef<'a> {
// derive Debug on such a type could here generate code
// that needs the feature gate enabled.)
cx.expr_unreachable(sp)
expr_unreachable_intrinsic(cx, sp)
}
else {