From dcbe85abad8ddd3a39fcafe70a884db4e71f0b03 Mon Sep 17 00:00:00 2001 From: Yuki Okushi Date: Thu, 2 Jul 2020 02:37:52 +0900 Subject: [PATCH] Explain exhaustive matching on {usize,isize} maximum values --- .../hair/pattern/check_match.rs | 10 +++++++- ...-gate-precise_pointer_size_matching.stderr | 4 +++ ...non-exhaustive-pattern-pointer-size-int.rs | 21 ++++++++++++++++ ...exhaustive-pattern-pointer-size-int.stderr | 25 +++++++++++++++++++ 4 files changed, 59 insertions(+), 1 deletion(-) create mode 100644 src/test/ui/pattern/usefulness/non-exhaustive-pattern-pointer-size-int.rs create mode 100644 src/test/ui/pattern/usefulness/non-exhaustive-pattern-pointer-size-int.stderr diff --git a/src/librustc_mir_build/hair/pattern/check_match.rs b/src/librustc_mir_build/hair/pattern/check_match.rs index 6fc447a87f57..6a68c9158894 100644 --- a/src/librustc_mir_build/hair/pattern/check_match.rs +++ b/src/librustc_mir_build/hair/pattern/check_match.rs @@ -468,6 +468,7 @@ fn check_exhaustive<'p, 'tcx>( // In the case of an empty match, replace the '`_` not covered' diagnostic with something more // informative. let mut err; + let joined_patterns = joined_uncovered_patterns(&witnesses); if is_empty_match && !non_empty_enum { err = create_e0004( cx.tcx.sess, @@ -475,7 +476,6 @@ fn check_exhaustive<'p, 'tcx>( format!("non-exhaustive patterns: type `{}` is non-empty", scrut_ty), ); } else { - let joined_patterns = joined_uncovered_patterns(&witnesses); err = create_e0004( cx.tcx.sess, sp, @@ -490,6 +490,14 @@ fn check_exhaustive<'p, 'tcx>( possibly by adding wildcards or more match arms", ); err.note(&format!("the matched value is of type `{}`", scrut_ty)); + if (scrut_ty == cx.tcx.types.usize || scrut_ty == cx.tcx.types.isize) + && joined_patterns == "`_`" + { + err.note("for `usize` and `isize`, no assumptions about the maximum value are permitted"); + err.note( + "to exhaustively match on either pointer-size integer type, wildcards must be used", + ); + } err.emit(); } diff --git a/src/test/ui/feature-gates/feature-gate-precise_pointer_size_matching.stderr b/src/test/ui/feature-gates/feature-gate-precise_pointer_size_matching.stderr index 6c5d0091c5ad..8aa1534b2768 100644 --- a/src/test/ui/feature-gates/feature-gate-precise_pointer_size_matching.stderr +++ b/src/test/ui/feature-gates/feature-gate-precise_pointer_size_matching.stderr @@ -6,6 +6,8 @@ LL | match 0usize { | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms = note: the matched value is of type `usize` + = note: for `usize` and `isize`, no assumptions about the maximum value are permitted + = note: to exhaustively match on either pointer-size integer type, wildcards must be used error[E0004]: non-exhaustive patterns: `_` not covered --> $DIR/feature-gate-precise_pointer_size_matching.rs:10:11 @@ -15,6 +17,8 @@ LL | match 0isize { | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms = note: the matched value is of type `isize` + = note: for `usize` and `isize`, no assumptions about the maximum value are permitted + = note: to exhaustively match on either pointer-size integer type, wildcards must be used error: aborting due to 2 previous errors diff --git a/src/test/ui/pattern/usefulness/non-exhaustive-pattern-pointer-size-int.rs b/src/test/ui/pattern/usefulness/non-exhaustive-pattern-pointer-size-int.rs new file mode 100644 index 000000000000..aa6a3ffc522e --- /dev/null +++ b/src/test/ui/pattern/usefulness/non-exhaustive-pattern-pointer-size-int.rs @@ -0,0 +1,21 @@ +use std::{usize, isize}; + +fn main() { + match 0usize { + //~^ ERROR non-exhaustive patterns + //~| NOTE pattern `_` not covered + //~| NOTE the matched value is of type `usize` + //~| NOTE for `usize` and `isize`, no assumptions about the maximum value are permitted + //~| NOTE to exhaustively match on either pointer-size integer type, wildcards must be used + 0 ..= usize::MAX => {} + } + + match 0isize { + //~^ ERROR non-exhaustive patterns + //~| NOTE pattern `_` not covered + //~| NOTE the matched value is of type `isize` + //~| NOTE for `usize` and `isize`, no assumptions about the maximum value are permitted + //~| NOTE to exhaustively match on either pointer-size integer type, wildcards must be used + isize::MIN ..= isize::MAX => {} + } +} diff --git a/src/test/ui/pattern/usefulness/non-exhaustive-pattern-pointer-size-int.stderr b/src/test/ui/pattern/usefulness/non-exhaustive-pattern-pointer-size-int.stderr new file mode 100644 index 000000000000..cd47e74fa464 --- /dev/null +++ b/src/test/ui/pattern/usefulness/non-exhaustive-pattern-pointer-size-int.stderr @@ -0,0 +1,25 @@ +error[E0004]: non-exhaustive patterns: `_` not covered + --> $DIR/non-exhaustive-pattern-pointer-size-int.rs:4:11 + | +LL | match 0usize { + | ^^^^^^ pattern `_` not covered + | + = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms + = note: the matched value is of type `usize` + = note: for `usize` and `isize`, no assumptions about the maximum value are permitted + = note: to exhaustively match on either pointer-size integer type, wildcards must be used + +error[E0004]: non-exhaustive patterns: `_` not covered + --> $DIR/non-exhaustive-pattern-pointer-size-int.rs:13:11 + | +LL | match 0isize { + | ^^^^^^ pattern `_` not covered + | + = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms + = note: the matched value is of type `isize` + = note: for `usize` and `isize`, no assumptions about the maximum value are permitted + = note: to exhaustively match on either pointer-size integer type, wildcards must be used + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0004`.