Why Sigil Bans Shadowing

Sigil bans local shadowing because a name should not change meaning within the same lexical region of a program.

The Problem

Many languages allow an inner binding to reuse an outer name. That can be convenient, but it also means the same identifier may refer to different values across nested scopes. The compiler can track that correctly, but it still makes source harder to read, harder to explain, and easier to alter incorrectly during automated edits.

For Sigil, that tradeoff is not worth it. Shadowing introduces a representational choice that mostly benefits local convenience rather than clarity.

The Decision

Sigil requires fresh names instead of allowing inner scopes to reuse outer ones. That rule applies across locals, lambda parameters, and pattern bindings.

Why This Fits Sigil

This is less about scope theory than about source stability. A name should carry one meaning through the part of the program where it is visible. That is easier for readers, easier for refactors, and easier for generation tools that work by editing existing code.

The language gives up a common convenience, but it gains a clearer local naming model in return.