Ensure that units are compatible with themselves (#2975)

As pointed out by @stof in #2951 (review).
sass · Dec 21, 2020 · 65a137b · 65a137b
1 parent 150d805
commit 65a137b
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/spec/types/number.md b/spec/types/number.md
@@ -47,8 +47,8 @@ The following conversion factors are defined:
 
 ### Compatible Units
 
-Two units are said to be "compatible" if their [conversion factors] have the
-same unit.
+Two units are said to be "compatible" if they are identical or if their
+[conversion factors] have the same unit.
 
 [conversion factors]: #conversion-factors
 
@@ -67,6 +67,8 @@ have a conversion factor.
 
   * Otherwise, throw an error.
 
+* If `number`'s unit is `unit`, return `number` as-is.
+
 * Let `number-factor` be `number`'s unit's conversion factor. If `number`
   doesn't have a unit or that unit doesn't have a conversion factor, throw an
   error.