Purely from a reader's perspective, yes, an IDE can probably parse and highlight mutable variables automatically.
But from a writer's, modifier's or refactorer's perspective, what counts is the intent. Was a particular local variable meant to be mutable or immutable? Everytime I write a line of code, I need to watch out whether I mutated a variable which was not meant to be mutated. Or even the case where I myself mutate it unintentionally (by a typo, for example).
In a non-trivial project having a code-base with 100K lines of code, the time and effort spent in this manual analysis can be an overhead that might be well worth avoiding.
Comments
Purely from a reader's perspective, yes, an IDE can probably parse and highlight mutable variables automatically.
But from a writer's, modifier's or refactorer's perspective, what counts is the intent. Was a particular local variable meant to be mutable or immutable? Everytime I write a line of code, I need to watch out whether I mutated a variable which was not meant to be mutated. Or even the case where I myself mutate it unintentionally (by a typo, for example).
In a non-trivial project having a code-base with 100K lines of code, the time and effort spent in this manual analysis can be an overhead that might be well worth avoiding.