[CSS Min/Max] Use CssMinMax instead of MinMaxExpression in CalcValue

accepted/min-max.changes.md

@@ -1,3 +1,9 @@
+## Draft 3
+
+* Use `CssMinMax` instead of `MinMaxExpression` as a possibility for
+  `CalcValue`. We don't want SassScript funtion invocations in plain CSS math
+  functions.
+
 ## Draft 2
 
 * Fix a typo where `CalcValue` was incorrectly referred to as `CalcArithemtic`.

accepted/min-max.md

@@ -1,4 +1,4 @@
-# Plain CSS `min()` and `max()`: Draft 2
+# Plain CSS `min()` and `max()`: Draft 3
 
 *([Issue](https://github.com/sass/sass/issues/2378), [Changelog](min-max.changes.md))*
 
@@ -85,7 +85,7 @@ The grammar for this production is:
 **CalcValue**        ::= CalcValue (('+' | '-' | '*' | '/') CalcValue)+
                    | '(' CalcValue ')'
                    | ('calc(' | 'env(' | 'var(') InterpolatedDeclarationValue ')'
-                   | MinMaxExpression
+                   | CssMinMax
                    | Interpolation
                    | Number
 </pre></x>