From 8f9348ee533229fe0b85aa23b1cf2fc94098b6f9 Mon Sep 17 00:00:00 2001
From: Fabian Homborg <FHomborg@gmail.com>
Date: Wed, 18 May 2022 18:47:10 +0200
Subject: [PATCH] Make `eval` a reserved keyword

Like `set` and `read` before it, `eval` can be used to set variables,
and so it can't be shadowed by a function without loss of
functionality.

So this forbids it.

Incidentally, this means we will no longer try to autoload an
`eval.fish` file that's left over from an old version, which would
have helped with #8963.
---
 src/parser_keywords.cpp |  2 +-
 tests/checks/eval.fish  | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/parser_keywords.cpp b/src/parser_keywords.cpp
index d3e3f6a93..810fa6b5f 100644
--- a/src/parser_keywords.cpp
+++ b/src/parser_keywords.cpp
@@ -24,7 +24,7 @@ static const string_set_t block_keywords = {L"for",      L"while",  L"if",
 
 static const wcstring reserved_keywords[] = {
     L"end",  L"case",   L"else", L"return", L"continue", L"break", L"argparse",
-    L"read", L"string", L"set",  L"status", L"test",     L"[",     L"_"};
+    L"read", L"string", L"set",  L"status", L"test", L"[", L"_", L"eval"};
 
 // The lists above are purposely implemented separately from the logic below, so that future
 // maintainers may assume the contents of the list based off their names, and not off what the
diff --git a/tests/checks/eval.fish b/tests/checks/eval.fish
index db43ebd18..86ec3c6c6 100644
--- a/tests/checks/eval.fish
+++ b/tests/checks/eval.fish
@@ -60,3 +60,25 @@ echo empty block eval: $status # 0
 source /banana/\t/foo
 # CHECKERR: source: Error encountered while sourcing file '/banana/\t/foo':
 # CHECKERR: source: No such file or directory
+
+# See that eval can't be defined as a function
+function eval
+    builtin eval $argv
+end
+# CHECKERR: checks/eval.fish (line {{\d+}}): function: eval: cannot use reserved keyword as function name
+# CHECKERR: function eval
+# CHECKERR: ^
+
+
+function evil --no-scope-shadowing
+    eval $argv
+end
+
+# And this is why we do this: `eval` *can't* be cleanly shadowed with a function,
+# because that would always introduce a new block or at the very least clobber $argv.
+eval set -l argv this works
+echo $argv
+# CHECK: this works
+evil set -l argv this does not
+echo $argv
+# CHECK: this works