tree 6d39001b52c844ef3cc5d3274ef87564406fde02
parent b960c4cb1af8e5626be487320337a54137473dca
author Peter Weinberger <pjw@google.com> 1790717463 -0400
committer Peter Weinberger <pjw@google.com> 1791834324 -0700

gopls/internal/analysis/unusedvariable: remove assignments to unused variables

If a variable is declared and assigned to, but never read, the
compiler reports it as unused. Previously, unusedvariable only
removed the variable's declaration, leaving behind invalid assignments
to an undeclared variable.

Now, unusedvariable also calls refactor.DeleteVar on any remaining LHS
uses of the variable. To support this, DeleteVar is extended to handle
'=' assignments and redeclarations in ':=' statements, and to simplify
assignments whose remaining LHS consists only of blank identifiers
(like "_ = f()" or "_, _ = f()") to expression statements when the RHS
is a valid statement.

Fixes golang/go#81809

Change-Id: I8dffa42e20f79998038befe16929c18226526978
Reviewed-on: https://go-review.googlesource.com/c/tools/+/841565
Reviewed-by: Madeline Kalil <mkalil@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>