From 9b1bdf2db8798c024e6fbe84d4144c04f61d80c7 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Sun, 19 Aug 2018 11:59:49 +0200
Subject: [PATCH] FIx floating point evaluation

Fixes #2361.
---
 src/libexpr/primops.cc         | 9 +++++++++
 tests/lang/eval-okay-float.exp | 1 +
 tests/lang/eval-okay-float.nix | 6 ++++++
 3 files changed, 16 insertions(+)
 create mode 100644 tests/lang/eval-okay-float.exp
 create mode 100644 tests/lang/eval-okay-float.nix

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 8ace6db4d..6f82c6c40 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1680,6 +1680,8 @@ static void prim_concatMap(EvalState & state, const Pos & pos, Value * * args, V
 
 static void prim_add(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
+    state.forceValue(*args[0], pos);
+    state.forceValue(*args[1], pos);
     if (args[0]->type == tFloat || args[1]->type == tFloat)
         mkFloat(v, state.forceFloat(*args[0], pos) + state.forceFloat(*args[1], pos));
     else
@@ -1689,6 +1691,8 @@ static void prim_add(EvalState & state, const Pos & pos, Value * * args, Value &
 
 static void prim_sub(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
+    state.forceValue(*args[0], pos);
+    state.forceValue(*args[1], pos);
     if (args[0]->type == tFloat || args[1]->type == tFloat)
         mkFloat(v, state.forceFloat(*args[0], pos) - state.forceFloat(*args[1], pos));
     else
@@ -1698,6 +1702,8 @@ static void prim_sub(EvalState & state, const Pos & pos, Value * * args, Value &
 
 static void prim_mul(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
+    state.forceValue(*args[0], pos);
+    state.forceValue(*args[1], pos);
     if (args[0]->type == tFloat || args[1]->type == tFloat)
         mkFloat(v, state.forceFloat(*args[0], pos) * state.forceFloat(*args[1], pos));
     else
@@ -1707,6 +1713,9 @@ static void prim_mul(EvalState & state, const Pos & pos, Value * * args, Value &
 
 static void prim_div(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
+    state.forceValue(*args[0], pos);
+    state.forceValue(*args[1], pos);
+
     NixFloat f2 = state.forceFloat(*args[1], pos);
     if (f2 == 0) throw EvalError(format("division by zero, at %1%") % pos);
 
diff --git a/tests/lang/eval-okay-float.exp b/tests/lang/eval-okay-float.exp
new file mode 100644
index 000000000..3c50a8adc
--- /dev/null
+++ b/tests/lang/eval-okay-float.exp
@@ -0,0 +1 @@
+[ 3.4 3.5 2.5 1.5 ]
diff --git a/tests/lang/eval-okay-float.nix b/tests/lang/eval-okay-float.nix
new file mode 100644
index 000000000..b2702c7b1
--- /dev/null
+++ b/tests/lang/eval-okay-float.nix
@@ -0,0 +1,6 @@
+[
+  (1.1 + 2.3)
+  (builtins.add (0.5 + 0.5) (2.0 + 0.5))
+  ((0.5 + 0.5) * (2.0 + 0.5))
+  ((1.5 + 1.5) / (0.5 * 4.0))
+]