Fixed a bug in promotion involving ContextUnits where promotion conte…

…xt might not be retained.
PainterQubits · Apr 5, 2017 · 00fe499 · 00fe499
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commit 00fe499
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Showing 3 changed files with 8 additions and 2 deletions.
diff --git a/NEWS.md b/NEWS.md
@@ -1,3 +1,6 @@
+- v0.2.2
+  - Fixed a bug in promotion involving `ContextUnits` where the promotion context might
+    not be properly retained.
 - v0.2.1
   - Fixed `isapprox` bug [#74](https://github.com/ajkeller34/Unitful.jl/pull/74).
   - Added `DimensionlessQuantity` methods for `exp`, `exp10`, `exp2`, `expm1`, `log1p`,

diff --git a/src/Promotion.jl b/src/Promotion.jl
@@ -164,8 +164,9 @@ function Base.promote_rule{S1,S2,D,U1,U2}(::Type{Quantity{S1,D,U1}},
         typeof(convfact(p,U1())), typeof(convfact(p,U2())))
     if !isunitless(p)
         if U1 <: ContextUnits && U2 <: ContextUnits
-            if upreferred(U1()) === upreferred(U2())
-                return Quantity{numtype,D,typeof(ContextUnits(p,p))}
+            up1 = upreferred(U1())
+            if up1 === upreferred(U2())
+                return Quantity{numtype,D,typeof(ContextUnits(p,up1))}
             else
                 return Quantity{numtype,D,typeof(p)}
             end

diff --git a/test/runtests.jl b/test/runtests.jl
@@ -267,6 +267,8 @@ end
         μm2mm = ContextUnits(μm,mm)
         @test @inferred(promote(1.0nm2μm, 1.0m)) === (0.001μm2μm, 1e6μm2μm)
         @test @inferred(promote(1.0m, 1.0μm2μm)) === (1e6μm2μm, 1.0μm2μm)
+        @test ===(upreferred.(unit.(promote(1.0nm2μm, 2nm2μm)))[1], ContextUnits(μm,μm))
+        @test ===(upreferred.(unit.(promote(1.0nm2μm, 2nm2μm)))[2], ContextUnits(μm,μm))
 
         # Context agreement
         @test @inferred(promote(1.0nm2μm, 1.0μm2μm)) ===