[css-values-5] Set the types correctly for progress fucntions and calc-mix(). w3c#10017

Author: tabatkins

css-values-5/Overview.bs

@@ -158,8 +158,10 @@ Calculated Progress Values: the ''progress()'' notation</h3>
 	(the [=progress start value=]
 	and [=progress end value=]).
 	The argument [=calculations=] can resolve to any <<number>>, <<dimension>>, or <<percentage>>,
-	but must have the same [=determine the type of a calculation|type=],
+	but must have a [=consistent type=]
 	or else the function is invalid.
+	The result will be a <<number>>,
+	[=made consistent=] with the [=consistent type=] of the arguments.
 
 	The syntax of ''progress()'' is defined as follows:
 
@@ -208,6 +210,12 @@ Media Query Progress Values: the ''media-progress()'' notation</h3>
 	must be valid values for the specified [=media query=],
 	or else the function is invalid.
 
+	The two input [=calculations=]
+	but must have a [=consistent type=]
+	or else the function is invalid.
+	The result will be a <<number>>,
+	[=made consistent=] with the [=consistent type=] of the arguments.
+
 <h3 id="container-progress-func">
 Container Query Progress Values: the ''container-progress()'' notation</h3>
 
@@ -226,6 +234,12 @@ Container Query Progress Values: the ''container-progress()'' notation</h3>
 	the named containers to consider when selecting a container
 	to resolve against.
 
+	The two input [=calculations=]
+	but must have a [=consistent type=]
+	or else the function is invalid.
+	The result will be a <<number>>,
+	[=made consistent=] with the [=consistent type=] of the arguments.
+
 	If no appropriate containers are found,
 	''container-progress()'' resolves its <<size-feature>> query
 	against the [=small viewport size=].
@@ -353,8 +367,15 @@ Interpolated Numeric and Dimensional Values: the ''calc-mix()'' notation</h3>
 
 	The <<calc-sum>> arguments can resolve
 	to any <<number>>, <<dimension>>, or <<percentage>>,
-	but must have the same [=determine the type of a calculation|type=],
+	but must have a [=consistent type=]
 	or else the function is invalid.
+	The result's type will be the [=consistent type=].
+
+	Issue: This return type doesn't correctly capture the possibility
+	that the <<progress>>,
+	via one of the progress fucntions,
+	invokes a volatile percentage
+	that could potentially trigger "behaves as auto" behavior.
 
 	The [=used value=] of a valid ''calc-mix()'' is
 	the result of interpolating these two values