fix: allow lexical import shadowing

docs/spec.md

@@ -336,6 +336,21 @@ ImportPath    = ident { "." ident } .
   lookup rather than package-name diagnostics. Builtin spelling does not alter
   the object: an import bound as `len`, `size`, `align`, or another builtin name
   remains a selector-only package-name object.
+  An ordinary lexical binding may shadow that file-local package-name object.
+  Lookup at each occurrence chooses the nearest enclosing binding: a selector
+  before a later local declaration can use and count the import, while the
+  same spelling after that declaration denotes the local. Parameters bind for
+  their whole function body; local `let` bindings begin after their declared
+  type and initializer have been checked; tuple bindings begin after their
+  right-hand side and declared types; and loop, range, and match-arm bindings
+  begin only after their respective initializer/iterable or pattern/type has
+  been checked. Nested blocks and loop scopes restore the imported package-name
+  object on exit. These declaration-point rules apply equally to default,
+  explicit, and builtin-spelled qualifiers. A selector counts as an import use
+  only when its receiver resolves to that package-name object; a selector on a
+  closer local, including a field or pseudo-field selector, does not.
+  Go has no range-loop `else` clause; that WW-only extension is not assigned a
+  Go-derived scope rule by this paragraph.
   Neither form exposes an imported declaration as a bare `Name`; ordinary
   unqualified lookup remains limited to lexical, builtin, and same-package
   declarations. A blank import creates no package-name object, an effective