bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

Rollup merge of #121823 - Nadrieril:never-witnesses, r=compiler-errors

Browse source 
never patterns: suggest `!` patterns on non-exhaustive matches

When a match is non-exhaustive we now suggest never patterns whenever it makes sense.

r? ``@compiler-errors``
This commit is contained in:
Matthias Krüger 2024-03-18 22:24:36 +01:00 • committed by GitHub
commit 2d3dcfaade
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
11 changed files with 982 additions and 242 deletions
Download patch file Download diff file Expand all files Collapse all files

74
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View file

@ -938,9 +938,6 @@ fn report_non_exhaustive_match<'p, 'tcx>(
};
// In the case of an empty match, replace the '`_` not covered' diagnostic with something more
// informative.
let mut err;
let pattern;
let patterns_len;
if is_empty_match && !non_empty_enum {
return cx.tcx.dcx().emit_err(NonExhaustivePatternsTypeNotEmpty {
cx,
@ -948,33 +945,23 @@ fn report_non_exhaustive_match<'p, 'tcx>(
span: sp,
ty: scrut_ty,
});
} else {
// FIXME: migration of this diagnostic will require list support
let joined_patterns = joined_uncovered_patterns(cx, &witnesses);
err = create_e0004(
cx.tcx.sess,
sp,
format!("non-exhaustive patterns: {joined_patterns} not covered"),
);
err.span_label(
sp,
format!(
"pattern{} {} not covered",
rustc_errors::pluralize!(witnesses.len()),
joined_patterns
),
);
patterns_len = witnesses.len();
pattern = if witnesses.len() < 4 {
witnesses
.iter()
.map(|witness| cx.hoist_witness_pat(witness).to_string())
.collect::<Vec<String>>()
.join(" | ")
} else {
"_".to_string()
};
};
}
// FIXME: migration of this diagnostic will require list support
let joined_patterns = joined_uncovered_patterns(cx, &witnesses);
let mut err = create_e0004(
cx.tcx.sess,
sp,
format!("non-exhaustive patterns: {joined_patterns} not covered"),
);
err.span_label(
sp,
format!(
"pattern{} {} not covered",
rustc_errors::pluralize!(witnesses.len()),
joined_patterns
),
);
// Point at the definition of non-covered `enum` variants.
if let Some(AdtDefinedHere { adt_def_span, ty, variants }) =
@ -1021,6 +1008,23 @@ fn report_non_exhaustive_match<'p, 'tcx>(
}
}
// Whether we suggest the actual missing patterns or `_`.
let suggest_the_witnesses = witnesses.len() < 4;
let suggested_arm = if suggest_the_witnesses {
let pattern = witnesses
.iter()
.map(|witness| cx.hoist_witness_pat(witness).to_string())
.collect::<Vec<String>>()
.join(" | ");
if witnesses.iter().all(|p| p.is_never_pattern()) && cx.tcx.features().never_patterns {
// Arms with a never pattern don't take a body.
pattern
} else {
format!("{pattern} => todo!()")
}
} else {
format!("_ => todo!()")
};
let mut suggestion = None;
let sm = cx.tcx.sess.source_map();
match arms {
@ -1033,7 +1037,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
};
suggestion = Some((
sp.shrink_to_hi().with_hi(expr_span.hi()),
format!(" {{{indentation}{more}{pattern} => todo!(),{indentation}}}",),
format!(" {{{indentation}{more}{suggested_arm},{indentation}}}",),
));
}
[only] => {
@ -1059,7 +1063,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
};
suggestion = Some((
only.span.shrink_to_hi(),
format!("{comma}{pre_indentation}{pattern} => todo!()"),
format!("{comma}{pre_indentation}{suggested_arm}"),
));
}
[.., prev, last] => {
@ -1082,7 +1086,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
if let Some(spacing) = spacing {
suggestion = Some((
last.span.shrink_to_hi(),
format!("{comma}{spacing}{pattern} => todo!()"),
format!("{comma}{spacing}{suggested_arm}"),
));
}
}
@ -1093,13 +1097,13 @@ fn report_non_exhaustive_match<'p, 'tcx>(
let msg = format!(
"ensure that all possible cases are being handled by adding a match arm with a wildcard \
pattern{}{}",
if patterns_len > 1 && patterns_len < 4 && suggestion.is_some() {
if witnesses.len() > 1 && suggest_the_witnesses && suggestion.is_some() {
", a match arm with multiple or-patterns"
} else {
// we are either not suggesting anything, or suggesting `_`
""
},
match patterns_len {
match witnesses.len() {
// non-exhaustive enum case
0 if suggestion.is_some() => " as shown",
0 => "",