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NadrierilNadrieril
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Rework error handling when lowering range endpoints
1 parent c5e1702 commit 1e1174b

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1 file changed

+87
-114
lines changed
  • compiler/rustc_mir_build/src/thir/pattern

1 file changed

+87
-114
lines changed

‎compiler/rustc_mir_build/src/thir/pattern/mod.rs‎

Lines changed: 87 additions & 114 deletions
Original file line numberDiff line numberDiff line change
@@ -27,7 +27,7 @@ use rustc_middle::ty::CanonicalUserTypeAnnotation;
2727
use rustc_middle::ty::TypeVisitableExt;
2828
use rustc_middle::ty::{self, AdtDef, Region, Ty, TyCtxt, UserType};
2929
use rustc_middle::ty::{GenericArg, GenericArgsRef};
30-
use rustc_span::{Span, Symbol};
30+
use rustc_span::{ErrorGuaranteed, Span, Symbol};
3131
use rustc_target::abi::FieldIdx;
3232

3333
use std::cmp::Ordering;
@@ -85,127 +85,126 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
8585
)
8686
}
8787

88-
fn lower_range_expr(
88+
fn lower_pattern_range_endpoint(
8989
&mut self,
90-
expr: &'tcx hir::Expr<'tcx>,
91-
) -> (PatKind<'tcx>, Option<Ascription<'tcx>>) {
92-
match self.lower_lit(expr) {
93-
PatKind::AscribeUserType { ascription, subpattern: box Pat { kind, .. } } => {
94-
(kind, Some(ascription))
90+
expr: Option<&'tcx hir::Expr<'tcx>>,
91+
) -> Result<(Option<mir::Const<'tcx>>, Option<Ascription<'tcx>>), ErrorGuaranteed> {
92+
match expr {
93+
None => Ok((None, None)),
94+
Some(expr) => {
95+
let (kind, ascr) = match self.lower_lit(expr) {
96+
PatKind::AscribeUserType { ascription, subpattern: box Pat { kind, .. } } => {
97+
(kind, Some(ascription))
98+
}
99+
kind => (kind, None),
100+
};
101+
let value = if let PatKind::Constant { value } = kind {
102+
value
103+
} else {
104+
let msg = format!(
105+
"found bad range pattern endpoint `{expr:?}` outside of error recovery"
106+
);
107+
return Err(self.tcx.sess.delay_span_bug(expr.span, msg));
108+
};
109+
Ok((Some(value), ascr))
95110
}
96-
kind => (kind, None),
97111
}
98112
}
99113

100114
fn lower_pattern_range(
101115
&mut self,
102-
ty: Ty<'tcx>,
103-
lo: mir::Const<'tcx>,
104-
hi: mir::Const<'tcx>,
116+
lo_expr: Option<&'tcx hir::Expr<'tcx>>,
117+
hi_expr: Option<&'tcx hir::Expr<'tcx>>,
105118
end: RangeEnd,
119+
ty: Ty<'tcx>,
106120
span: Span,
107-
lo_expr: Option<&hir::Expr<'tcx>>,
108-
hi_expr: Option<&hir::Expr<'tcx>>,
109-
) -> PatKind<'tcx> {
121+
) -> Result<PatKind<'tcx>, ErrorGuaranteed> {
122+
if lo_expr.is_none() && hi_expr.is_none() {
123+
let msg = format!("found twice-open range pattern (`..`) outside of error recovery");
124+
return Err(self.tcx.sess.delay_span_bug(span, msg));
125+
}
126+
127+
let (lo, lo_ascr) = self.lower_pattern_range_endpoint(lo_expr)?;
128+
let (hi, hi_ascr) = self.lower_pattern_range_endpoint(hi_expr)?;
129+
130+
let lo = lo.unwrap_or_else(|| {
131+
// Unwrap is ok because the type is known to be numeric.
132+
let lo = ty.numeric_min_val(self.tcx).unwrap();
133+
mir::Const::from_ty_const(lo, self.tcx)
134+
});
135+
let hi = hi.unwrap_or_else(|| {
136+
// Unwrap is ok because the type is known to be numeric.
137+
let hi = ty.numeric_max_val(self.tcx).unwrap();
138+
mir::Const::from_ty_const(hi, self.tcx)
139+
});
110140
assert_eq!(lo.ty(), ty);
111141
assert_eq!(hi.ty(), ty);
142+
112143
let cmp = compare_const_vals(self.tcx, lo, hi, self.param_env);
113-
let max = || {
114-
self.tcx
115-
.layout_of(self.param_env.with_reveal_all_normalized(self.tcx).and(ty))
116-
.ok()
117-
.unwrap()
118-
.size
119-
.unsigned_int_max()
120-
};
121-
match (end, cmp) {
144+
let mut kind = match (end, cmp) {
122145
// `x..y` where `x < y`.
123146
// Non-empty because the range includes at least `x`.
124147
(RangeEnd::Excluded, Some(Ordering::Less)) => {
125148
PatKind::Range(Box::new(PatRange { lo, hi, end }))
126149
}
127-
// `x..y` where `x >= y`. The range is empty => error.
128-
(RangeEnd::Excluded, _) => {
129-
let mut lower_overflow = false;
130-
let mut higher_overflow = false;
131-
if let Some(hir::Expr { kind: hir::ExprKind::Lit(lit), .. }) = lo_expr
132-
&& let rustc_ast::ast::LitKind::Int(val, _) = lit.node
133-
{
134-
if lo.eval_bits(self.tcx, self.param_env) != val {
135-
lower_overflow = true;
136-
self.tcx.sess.emit_err(LiteralOutOfRange { span: lit.span, ty, max: max() });
137-
}
138-
}
139-
if let Some(hir::Expr { kind: hir::ExprKind::Lit(lit), .. }) = hi_expr
140-
&& let rustc_ast::ast::LitKind::Int(val, _) = lit.node
141-
{
142-
if hi.eval_bits(self.tcx, self.param_env) != val {
143-
higher_overflow = true;
144-
self.tcx.sess.emit_err(LiteralOutOfRange { span: lit.span, ty, max: max() });
145-
}
146-
}
147-
if !lower_overflow && !higher_overflow {
148-
self.tcx.sess.emit_err(LowerRangeBoundMustBeLessThanUpper { span });
149-
}
150-
PatKind::Wild
151-
}
152150
// `x..=y` where `x == y`.
153151
(RangeEnd::Included, Some(Ordering::Equal)) => PatKind::Constant { value: lo },
154152
// `x..=y` where `x < y`.
155153
(RangeEnd::Included, Some(Ordering::Less)) => {
156154
PatKind::Range(Box::new(PatRange { lo, hi, end }))
157155
}
158-
// `x..=y` where `x > y` hence the range is empty => error.
159-
(RangeEnd::Included, _) => {
160-
let mut lower_overflow = false;
161-
let mut higher_overflow = false;
156+
// `x..y` where `x >= y`, or `x..=y` where `x > y`. The range is empty => error.
157+
_ => {
158+
let max = || {
159+
self.tcx
160+
.layout_of(self.param_env.with_reveal_all_normalized(self.tcx).and(ty))
161+
.ok()
162+
.unwrap()
163+
.size
164+
.unsigned_int_max()
165+
};
166+
// Emit a different message if there was overflow.
162167
if let Some(hir::Expr { kind: hir::ExprKind::Lit(lit), .. }) = lo_expr
163168
&& let rustc_ast::ast::LitKind::Int(val, _) = lit.node
164169
{
165170
if lo.eval_bits(self.tcx, self.param_env) != val {
166-
lower_overflow = true;
167-
self.tcx.sess.emit_err(LiteralOutOfRange { span: lit.span, ty, max: max() });
171+
return Err(self.tcx.sess.emit_err(LiteralOutOfRange { span: lit.span, ty, max: max() }));
168172
}
169173
}
170174
if let Some(hir::Expr { kind: hir::ExprKind::Lit(lit), .. }) = hi_expr
171175
&& let rustc_ast::ast::LitKind::Int(val, _) = lit.node
172176
{
173177
if hi.eval_bits(self.tcx, self.param_env) != val {
174-
higher_overflow = true;
175-
self.tcx.sess.emit_err(LiteralOutOfRange { span: lit.span, ty, max: max() });
178+
return Err(self.tcx.sess.emit_err(LiteralOutOfRange { span: lit.span, ty, max: max() }));
176179
}
177180
}
178-
if !lower_overflow && !higher_overflow {
179-
self.tcx.sess.emit_err(LowerRangeBoundMustBeLessThanOrEqualToUpper {
180-
span,
181-
teach: self.tcx.sess.teach(&error_code!(E0030)).then_some(()),
182-
});
183-
}
184-
PatKind::Wild
181+
let e = match end {
182+
RangeEnd::Included => {
183+
self.tcx.sess.emit_err(LowerRangeBoundMustBeLessThanOrEqualToUpper {
184+
span,
185+
teach: self.tcx.sess.teach(&error_code!(E0030)).then_some(()),
186+
})
187+
}
188+
RangeEnd::Excluded => {
189+
self.tcx.sess.emit_err(LowerRangeBoundMustBeLessThanUpper { span })
190+
}
191+
};
192+
return Err(e);
185193
}
186-
}
187-
}
194+
};
188195

189-
fn normalize_range_pattern_ends(
190-
&self,
191-
ty: Ty<'tcx>,
192-
lo: Option<&PatKind<'tcx>>,
193-
hi: Option<&PatKind<'tcx>>,
194-
) -> Option<(mir::Const<'tcx>, mir::Const<'tcx>)> {
195-
match (lo, hi) {
196-
(Some(PatKind::Constant { value: lo }), Some(PatKind::Constant { value: hi })) => {
197-
Some((*lo, *hi))
198-
}
199-
(Some(PatKind::Constant { value: lo }), None) => {
200-
let hi = ty.numeric_max_val(self.tcx)?;
201-
Some((*lo, mir::Const::from_ty_const(hi, self.tcx)))
202-
}
203-
(None, Some(PatKind::Constant { value: hi })) => {
204-
let lo = ty.numeric_min_val(self.tcx)?;
205-
Some((mir::Const::from_ty_const(lo, self.tcx), *hi))
196+
// If we are handling a range with associated constants (e.g.
197+
// `Foo::<'a>::A..=Foo::B`), we need to put the ascriptions for the associated
198+
// constants somewhere. Have them on the range pattern.
199+
for ascr in [lo_ascr, hi_ascr] {
200+
if let Some(ascription) = ascr {
201+
kind = PatKind::AscribeUserType {
202+
ascription,
203+
subpattern: Box::new(Pat { span, ty, kind }),
204+
};
206205
}
207-
_ => None,
208206
}
207+
Ok(kind)
209208
}
210209

211210
#[instrument(skip(self), level = "debug")]
@@ -220,37 +219,11 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
220219

221220
hir::PatKind::Range(ref lo_expr, ref hi_expr, end) => {
222221
let (lo_expr, hi_expr) = (lo_expr.as_deref(), hi_expr.as_deref());
223-
let lo_span = lo_expr.map_or(pat.span, |e| e.span);
224-
let lo = lo_expr.map(|e| self.lower_range_expr(e));
225-
let hi = hi_expr.map(|e| self.lower_range_expr(e));
226-
227-
let (lp, hp) = (lo.as_ref().map(|(x, _)| x), hi.as_ref().map(|(x, _)| x));
228-
let mut kind = match self.normalize_range_pattern_ends(ty, lp, hp) {
229-
Some((lc, hc)) => {
230-
self.lower_pattern_range(ty, lc, hc, end, lo_span, lo_expr, hi_expr)
231-
}
232-
None => {
233-
let msg = format!(
234-
"found bad range pattern `{:?}` outside of error recovery",
235-
(&lo, &hi),
236-
);
237-
self.tcx.sess.delay_span_bug(pat.span, msg);
238-
PatKind::Wild
239-
}
240-
};
241-
242-
// If we are handling a range with associated constants (e.g.
243-
// `Foo::<'a>::A..=Foo::B`), we need to put the ascriptions for the associated
244-
// constants somewhere. Have them on the range pattern.
245-
for end in &[lo, hi] {
246-
if let Some((_, Some(ascription))) = end {
247-
let subpattern = Box::new(Pat { span: pat.span, ty, kind });
248-
kind =
249-
PatKind::AscribeUserType { ascription: ascription.clone(), subpattern };
250-
}
251-
}
252-
253-
kind
222+
let span = lo_expr.map_or(span, |e| e.span);
223+
// FIXME?: returning `_` can cause inaccurate "unreachable" warnings. This can be
224+
// fixed by returning `PatKind::Const(ConstKind::Error(...))` if #115937 gets
225+
// merged.
226+
self.lower_pattern_range(lo_expr, hi_expr, end, ty, span).unwrap_or(PatKind::Wild)
254227
}
255228

256229
hir::PatKind::Path(ref qpath) => {

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