Issue #21994 has been updated by jneen (Jeanine Adkisson). I should say that I think the *worst* solution to this would be to warn in both cases. It would effectively require us to rewrite our DSL across every rule for every language we support. My ideal world is one where we could go back to using `rule /regex/ do ...` with no additional specification, or perhaps to warn in the division/modulo case instead. I would very much like to not have to turn off warnings while loading. ---------------------------------------- Bug #21994: If there is a local variable `foo`, calls to a method `foo` with a regexp literal as first argument is always a SyntaxError without parentheses https://bugs.ruby-lang.org/issues/21994#change-116992 * Author: jneen (Jeanine Adkisson) * Status: Open * ruby -v: 4.0.1 * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ## Quick version: ```bash ruby -e 'p /hello/' # => /hello/ (warning) ruby -e 'p = 1; p /hello/' # syntax error ruby -e 'p %r/hello/' # => /hello/ (no warning) ruby -e 'p = 1; p %r/hello/' # syntax error ``` ## Context In Rouge, our lexing DSL originally looked like this: ```ruby rule /some_regex/, Some::TokenType, :next_state rule /some_other_regex/ do |match| # custom action end ``` In a DSL context like this, I feel that using parentheses for *every* rule definition is a hassle and looks bad, so we leave them off, as is convention. Unfortunately, this warns: ``` warning: ambiguous `/`; wrap regexp in parentheses or add a space after `/` operator ``` Some time ago, to reduce warning-spam on users who run with `-w`, we transitioned all of these to use `%r/.../` or `%r(...)` syntax, which does not warn. The issue here I think is that *both* cases are equivalently ambiguous in some sense, which becomes apparent with the local-scope-dependent behaviour of the parser (putting aside that dependency on local variable scope makes the Ruby syntax highlighting of Rouge more or less impossible to do correctly without a full parse). If there is a local variable named `rule` introduced at any point, even several block scopes above, the entire file errors out in a very confusing manner. At the very least, I feel that the warnings here are inconsistent. If both cases truly are ambiguous and dependent on local variable scope, perhaps it would be better to warn on both - though that would make using a regex literal as a first argument *always* require parentheses to avoid warnings, which would make my DSL much harder. I'm honestly not entirely sure what a good solution would be, but I would like to open a discussion on the topic. Perhaps philosophically related to the other bug I have open ( #21870 ) - is this truly worthy of a warning, or should this be a linter concern? -- https://bugs.ruby-lang.org/

Issue #21994 has been updated by tompng (tomoya ishida). I think checking code validness is hard for the code below. Warning check is triggered at every line, each check needs to parse till the bottom. ~~~ruby a -1 => b # only a(-1 => b) is valid, (a - 1) => b is invalid at the `2 => 3` position b -1 => c # only b(-1 => c) is valid c -1 => d # only c(-1 => d) is valid d -1 => e, 2 => 3 # invalid if local variable d is defined ~~~ ---------------------------------------- Bug #21994: If there is a local variable `foo`, calls to a method `foo` with a regexp literal as first argument is always a SyntaxError without parentheses https://bugs.ruby-lang.org/issues/21994#change-117006 * Author: jneen (Jeanine Adkisson) * Status: Open * ruby -v: 4.0.1 * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ## Quick version: ```bash ruby -e 'p /hello/' # => /hello/ (warning) ruby -e 'p = 1; p /hello/' # syntax error ruby -e 'p %r/hello/' # => /hello/ (no warning) ruby -e 'p = 1; p %r/hello/' # syntax error ``` ## Context In Rouge, our lexing DSL originally looked like this: ```ruby rule /some_regex/, Some::TokenType, :next_state rule /some_other_regex/ do |match| # custom action end ``` In a DSL context like this, I feel that using parentheses for *every* rule definition is a hassle and looks bad, so we leave them off, as is convention. Unfortunately, this warns: ``` warning: ambiguous `/`; wrap regexp in parentheses or add a space after `/` operator ``` Some time ago, to reduce warning-spam on users who run with `-w`, we transitioned all of these to use `%r/.../` or `%r(...)` syntax, which does not warn. The issue here I think is that *both* cases are equivalently ambiguous in some sense, which becomes apparent with the local-scope-dependent behaviour of the parser (putting aside that dependency on local variable scope makes the Ruby syntax highlighting of Rouge more or less impossible to do correctly without a full parse). If there is a local variable named `rule` introduced at any point, even several block scopes above, the entire file errors out in a very confusing manner. At the very least, I feel that the warnings here are inconsistent. If both cases truly are ambiguous and dependent on local variable scope, perhaps it would be better to warn on both - though that would make using a regex literal as a first argument *always* require parentheses to avoid warnings, which would make my DSL much harder. I'm honestly not entirely sure what a good solution would be, but I would like to open a discussion on the topic. Perhaps philosophically related to the other bug I have open ( #21870 ) - is this truly worthy of a warning, or should this be a linter concern? -- https://bugs.ruby-lang.org/

Issue #21994 has been updated by matz (Yukihiro Matsumoto). I agree the current behavior is inconsistent, and I am now inclined to simply remove the `ambiguous /` warning. The warning was intended to be helpful, but as this issue shows, it does not catch the genuinely confusing case (the syntax error when a local variable shadows the method name), and it discourages a reasonable DSL style such as `rule /regex/ do ... end`. As tompng pointed out, deciding "whether the other interpretation would be valid" during lexical analysis is not practical. So my suggestion is to drop the `ambiguous /` warning and leave this kind of stylistic check to linters like RuboCop. The syntax error case is a separate problem that this warning never addressed anyway, so removing the warning does not make that situation worse. I would like to confirm this at the next dev meeting before changing it. Matz. ---------------------------------------- Bug #21994: If there is a local variable `foo`, calls to a method `foo` with a regexp literal as first argument is always a SyntaxError without parentheses https://bugs.ruby-lang.org/issues/21994#change-117325 * Author: jneen (Jeanine Adkisson) * Status: Open * ruby -v: 4.0.1 * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ## Quick version: ```bash ruby -e 'p /hello/' # => /hello/ (warning) ruby -e 'p = 1; p /hello/' # syntax error ruby -e 'p %r/hello/' # => /hello/ (no warning) ruby -e 'p = 1; p %r/hello/' # syntax error ``` ## Context In Rouge, our lexing DSL originally looked like this: ```ruby rule /some_regex/, Some::TokenType, :next_state rule /some_other_regex/ do |match| # custom action end ``` In a DSL context like this, I feel that using parentheses for *every* rule definition is a hassle and looks bad, so we leave them off, as is convention. Unfortunately, this warns: ``` warning: ambiguous `/`; wrap regexp in parentheses or add a space after `/` operator ``` Some time ago, to reduce warning-spam on users who run with `-w`, we transitioned all of these to use `%r/.../` or `%r(...)` syntax, which does not warn. The issue here I think is that *both* cases are equivalently ambiguous in some sense, which becomes apparent with the local-scope-dependent behaviour of the parser (putting aside that dependency on local variable scope makes the Ruby syntax highlighting of Rouge more or less impossible to do correctly without a full parse). If there is a local variable named `rule` introduced at any point, even several block scopes above, the entire file errors out in a very confusing manner. At the very least, I feel that the warnings here are inconsistent. If both cases truly are ambiguous and dependent on local variable scope, perhaps it would be better to warn on both - though that would make using a regex literal as a first argument *always* require parentheses to avoid warnings, which would make my DSL much harder. I'm honestly not entirely sure what a good solution would be, but I would like to open a discussion on the topic. Perhaps philosophically related to the other bug I have open ( #21870 ) - is this truly worthy of a warning, or should this be a linter concern? -- https://bugs.ruby-lang.org/