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rollup merge of #20039: barosl/if-let-friendly-error

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Fixes #19991.
This commit is contained in:
Alex Crichton 2014-12-21 00:04:13 -08:00
commit eb47e1e446
10 changed files with 64 additions and 24 deletions
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26
src/librustc_typeck/check/_match.rs
View file

@ -238,7 +238,8 @@ pub fn check_match<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
expr: &ast::Expr,
discrim: &ast::Expr,
arms: &[ast::Arm],
expected: Expectation<'tcx>) {
expected: Expectation<'tcx>,
match_src: ast::MatchSource) {
let tcx = fcx.ccx.tcx;
let discrim_ty = fcx.infcx().next_ty_var();
@ -290,12 +291,27 @@ pub fn check_match<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
if ty::type_is_error(result_ty) || ty::type_is_error(bty) {
ty::mk_err()
} else {
let (origin, expected, found) = match match_src {
/* if-let construct without an else block */
ast::MatchSource::IfLetDesugar { contains_else_clause }
if !contains_else_clause => (
infer::IfExpressionWithNoElse(expr.span),
bty,
result_ty,
),
_ => (
infer::MatchExpressionArm(expr.span, arm.body.span),
result_ty,
bty,
),
};
infer::common_supertype(
fcx.infcx(),
infer::MatchExpressionArm(expr.span, arm.body.span),
true, // result_ty is "expected" here
result_ty,
bty
origin,
true,
expected,
found,
)
}
});

4
src/librustc_typeck/check/mod.rs
View file

@ -3919,8 +3919,8 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
fcx.write_nil(id);
}
}
ast::ExprMatch(ref discrim, ref arms, _) => {
_match::check_match(fcx, expr, &**discrim, arms.as_slice(), expected);
ast::ExprMatch(ref discrim, ref arms, match_src) => {
_match::check_match(fcx, expr, &**discrim, arms.as_slice(), expected, match_src);
}
ast::ExprClosure(_, opt_kind, ref decl, ref body) => {
closure::check_expr_closure(fcx, expr, opt_kind, &**decl, &**body, expected);