Whitespace¶

interface Whitespace : KaSourceModificationLocality

Whitespace modification covers changes in whitespace and comments.

It usually has no effect, but it can affect compiler diagnostics. For example, when we have if (x) "a"else "b", the compiler produces the error "literals must be surrounded by whitespace" (see KT-82629). Changing it to if (x) "a" else "b" fixes the problem, but for the cached error to disappear, caches that can be affected by PSI-only changes need to be invalidated.

Whitespace modification is distinct from in-block modification. While in-block modification can affect both the syntax and the semantics of the code, whitespace modification is guaranteed to only have a syntactic effect and preserve semantics. (Whitespace deletions which might affect code semantics would be reported as InBlock or OutOfBlock.) Since just the PSI is affected, only the PSI-based subset of the compiler's checkers can be affected by such a change.

Whitespace modification can occur in any location. Even if it occurs outside a declaration, whitespace modification only affects its containing declaration or the file itself, not the whole module.