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Diffstat (limited to 'crates/ide_db/src/helpers/format_string.rs')
| -rw-r--r-- | crates/ide_db/src/helpers/format_string.rs | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/crates/ide_db/src/helpers/format_string.rs b/crates/ide_db/src/helpers/format_string.rs new file mode 100644 index 0000000000..c615d07250 --- /dev/null +++ b/crates/ide_db/src/helpers/format_string.rs @@ -0,0 +1,31 @@ +//! Tools to work with format string literals for the `format_args!` family of macros. +use syntax::{ast, AstNode, AstToken}; + +pub fn is_format_string(string: &ast::String) -> bool { + // Check if `string` is a format string argument of a macro invocation. + // `string` is a string literal, mapped down into the innermost macro expansion. + // Since `format_args!` etc. remove the format string when expanding, but place all arguments + // in the expanded output, we know that the string token is (part of) the format string if it + // appears in `format_args!` (otherwise it would have been mapped down further). + // + // This setup lets us correctly highlight the components of `concat!("{}", "bla")` format + // strings. It still fails for `concat!("{", "}")`, but that is rare. + + (|| { + let macro_call = string.syntax().ancestors().find_map(ast::MacroCall::cast)?; + let name = macro_call.path()?.segment()?.name_ref()?; + + if !matches!( + name.text().as_str(), + "format_args" | "format_args_nl" | "const_format_args" | "panic_2015" | "panic_2021" + ) { + return None; + } + + // NB: we match against `panic_2015`/`panic_2021` here because they have a special-cased arm for + // `"{}"`, which otherwise wouldn't get highlighted. + + Some(()) + })() + .is_some() +} |