Bug #21003: unexpected warning about ignored block

• Status: Closed
• Assignee: prism
• Target version: -
• ruby -v: ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [arm64-darwin24]
• Backport: 3.1: DONTNEED, 3.2: DONTNEED, 3.3: DONTNEED, 3.4: REQUIRED

[decuplet (Nikita Shilnikov)]

I stumbled upon this during the upgrade to 3.4. Here's the minimal repro:

$VERBOSE = true

def foo(*, &block) = block
def bar(buz, ...) = foo(buz, ...)

bar(:test) {}

It gives

ruby reproduce.rb
reproduce.rb:6: warning: the block passed to 'Object#bar' defined at reproduce.rb:4 may be ignored

where I believe it shouldn't. No warning reported if I change def bar(buz, ...) to def bar(...).

[byroot (Jean Boussier)]

• Backport changed from 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN to 3.1: DONTNEED, 3.2: DONTNEED, 3.3: DONTNEED, 3.4: REQUIRED

[ydah (Yudai Takada)]

memo) This does not occur even in Ruby 3.4.1 when --parser=parse.y.

❯ ruby --parser=parse.y -e '$VERBOSE = true

def foo(*, &block) = block
def bar(buz, ...) = foo(buz, ...)

bar(:test) {}'

~
❯ ruby --parser=parse.y -v -e '$VERBOSE = true

def foo(*, &block) = block
def bar(buz, ...) = foo(buz, ...)

bar(:test) {}'
ruby 3.4.1 (2024-12-25 revision 48d4efcb85) [arm64-darwin23]

[kddnewton (Kevin Newton)]

• Assignee set to prism

[kddnewton (Kevin Newton)]

• Status changed from Open to Closed

Applied in changeset git|2a1cff40f5e7875f69a7d0ed59eab92cc86c65ff.

---

Do not warn unused block when using forwarding

Fixes [Bug #21003]