Credence.Pattern.NoIfTrueFalse (credence v0.7.0)

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Detects redundant if/else wrappers around boolean expressions.

LLMs frequently emit this redundant boolean wrapper when the condition already evaluates to a boolean. An if whose do branch returns true and whose else branch returns false (or a wildcard default) is semantically identical to the condition itself.

Also catches the generalised forms where both branches are boolean expressions or literals.

Detected patterns

if condition do true else false end           → condition
if condition do bool_expr else false end       → condition and bool_expr
if condition do false else true end            → not condition
if condition do false else bool_expr end       → not condition and bool_expr
if condition do true else bool_expr end        → condition or bool_expr
if condition do bool_expr else true end        → not condition or bool_expr

Bad

if match?([_, _, _, _], parts) and Enum.all?(parts, &valid?/1) do
  true
else
  false
end

if x > 0 do
  y == 1
else
  false
end

if rem(year, 100) == 0 do
  rem(year, 400) == 0
else
  true
end

Good

match?([_, _, _, _], parts) and Enum.all?(parts, &valid?/1)

x > 0 and y == 1

rem(year, 100) != 0 or rem(year, 400) == 0

Auto-fix

  • if cond do true else false end → cond
  • if cond do expr else false end → cond and expr
  • if cond do false else true end → not cond
  • if cond do false else expr end → not cond and expr
  • if cond do true else expr end → cond or expr
  • if cond do expr else true end → not cond or expr