From 3edfe6090e9e15b205c21b19530607cbdcbbbe7a Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 11 Nov 2020 09:29:32 -0700
Subject: [PATCH] missing argument error

---
 src/libexpr/eval.cc    | 12 ++++++++++--
 src/libexpr/nixexpr.hh |  1 +
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 2b697882b..cf9f6c543 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -660,6 +660,14 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
     });
 }
 
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1))
+{
+    throw MissingArgumentError({
+        .hint = hintfmt(s, s1),
+        .errPos = pos
+    });
+}
+
 LocalNoInline(void addErrorTrace(Error & e, const char * s, const string & s2))
 {
     e.addTrace(std::nullopt, s, s2);
@@ -1365,7 +1373,7 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
             if (j != args.end()) {
                 actualArgs->attrs->push_back(*j);
             } else if (!i.def) {
-                throwUndefinedVarError(i.pos, R"(cannot auto-call a function that has an argument without a default value ('%1%')
+                throwMissingArgumentError(i.pos, R"(cannot auto-call a function that has an argument without a default value ('%1%')
 
 An 'auto-call' is when a nix expression is evaluated without any external arguments.
 If that nix expression is a function, and that function's arguments all have default
@@ -1373,7 +1381,7 @@ values, then all is well.
 
 But if the function arguments don't have default values, evaluation fails.
 
-The classic case for this error is evaluating a nix file with nix-build that expects
+The classic case for this error is evaluating a nix file that expects
 to be evaluated by callPackage.
   # in 'callPackage' format: expression is a function that takes an argument 'stdenv'.
   # callPackage would implicitly pull 'stdenv' from nixpkgs, then call this function.
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index e4cbc660f..bf2cd1f15 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -17,6 +17,7 @@ MakeError(ThrownError, AssertionError);
 MakeError(Abort, EvalError);
 MakeError(TypeError, EvalError);
 MakeError(UndefinedVarError, Error);
+MakeError(MissingArgumentError, Error);
 MakeError(RestrictedPathError, Error);