@lencheck macro

src/utils.jl

@@ -6,6 +6,24 @@ import NLPModels.increment!, NLPModels.decrement!
 using JuMP, MathOptInterface
 const MOI = MathOptInterface
 
+"""
+    @lencheck expected expr
+
+Macro to check that `length(expr) == expected` at runtime.
+Throws an ArgumentError with a helpful message when the lengths mismatch.
+Example:
+    @lencheck nlp.meta.nvar x
+"""
+macro lencheck(expected, var)
+  return esc(:(begin
+    _len_expected = $(expected)
+    _len_var = length($(var))
+    if _len_var != _len_expected
+      throw(ArgumentError("length($(QuoteNode(var))) = $( _len_var ) but expected $( _len_expected )"))
+    end
+  end))
+end
+
 # VariableIndex
 const VI = MOI.VariableIndex  # VariableIndex(value)