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improve error message when two-arg assert_eq! receives a trailing comma

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Previously, `assert_eq!(left, right,)` (respectively, `assert_ne!(left,
right,)`; note the trailing comma) would result in a confusing "requires
at least a format string argument" error. In reality, a format string is
optional, but the trailing comma puts us into the "match a token tree of
zero or more tokens" branch of the macro (in order to support the
optional format string), and passing the empty token tree into
`format_args!` results in the confusing error. If instead we match a
token tree of one or more tokens, we get a much more sensible
"unexpected end of macro invocation" error.

While we're here, fix up a stray space before a comma in the match
guards.

Resolves #39369.
This commit is contained in:
Zack M. Davis 2017-02-04 22:47:46 -08:00
parent d7777ae682
commit 65435e14fe
5 changed files with 44 additions and 6 deletions
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12
src/libcore/macros.rs
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@ -103,7 +103,7 @@ macro_rules! assert {
#[macro_export]
#[stable(feature = "rust1", since = "1.0.0")]
macro_rules! assert_eq {
($left:expr , $right:expr) => ({
($left:expr, $right:expr) => ({
match (&$left, &$right) {
(left_val, right_val) => {
if !(*left_val == *right_val) {
@ -113,13 +113,13 @@ macro_rules! assert_eq {
}
}
});
($left:expr , $right:expr, $($arg:tt)*) => ({
($left:expr, $right:expr, $($arg:tt)+) => ({
match (&($left), &($right)) {
(left_val, right_val) => {
if !(*left_val == *right_val) {
panic!("assertion failed: `(left == right)` \
(left: `{:?}`, right: `{:?}`): {}", left_val, right_val,
format_args!($($arg)*))
format_args!($($arg)+))
}
}
}
@ -146,7 +146,7 @@ macro_rules! assert_eq {
#[macro_export]
#[stable(feature = "assert_ne", since = "1.12.0")]
macro_rules! assert_ne {
($left:expr , $right:expr) => ({
($left:expr, $right:expr) => ({
match (&$left, &$right) {
(left_val, right_val) => {
if *left_val == *right_val {
@ -156,13 +156,13 @@ macro_rules! assert_ne {
}
}
});
($left:expr , $right:expr, $($arg:tt)*) => ({
($left:expr, $right:expr, $($arg:tt)+) => ({
match (&($left), &($right)) {
(left_val, right_val) => {
if *left_val == *right_val {
panic!("assertion failed: `(left != right)` \
(left: `{:?}`, right: `{:?}`): {}", left_val, right_val,
format_args!($($arg)*))
format_args!($($arg)+))
}
}
}