[css-values-4] Make the type-changing math functions also carry the percent hint of their inputs. #10017

Author: tabatkins

css-values-4/Overview.bs

@@ -3483,7 +3483,9 @@ Trigonometric Functions: ''sin()'', ''cos()'', ''tan()'', ''asin()'', ''acos()''
 	(That is, ''sin(45deg)'', ''sin(.125turn)'', and ''sin(3.14159 / 4)''
 	all represent the same value,
 	approximately ''.707''.)
-	They all represent a <<number>>;
+	They all represent a <<number>>,
+	with the return type [=made consistent=]
+	with the input [=calculation’s=] type.
 	''sin()'' and ''cos()'' will always return a number between −1 and 1,
 	while ''tan()'' can return any number between −∞ and +∞.
 	(See [[#calc-type-checking]] for details on how [=math functions=] handle ∞.)
@@ -3495,7 +3497,9 @@ Trigonometric Functions: ''sin()'', ''cos()'', ''tan()'', ''asin()'', ''acos()''
 	which must resolve to a <<number>>,
 	and compute their corresponding function,
 	interpreting their result as a number of radians,
-	representing an <<angle>>.
+	representing an <<angle>>
+	with the return type [=made consistent=]
+	with the input [=calculation’s=] type.
 	The angle returned by ''asin()'' must be normalized to the range [''-90deg'', ''90deg''];
 	the angle returned by ''acos()'' to the range [''0deg'', ''180deg''];
 	and the angle returned by ''atan()'' to the range [''-90deg'', ''90deg''].
@@ -3506,7 +3510,9 @@ Trigonometric Functions: ''sin()'', ''cos()'', ''tan()'', ''asin()'', ''acos()''
 	but must have a [=consistent type=]
 	or else the function is invalid.
 	The function returns the <<angle>>
-	between the positive X-axis and the point (B,A).
+	between the positive X-axis and the point (B,A),
+	with the return type [=made consistent=]
+	with the input [=calculation’s=] type.
 	The returned angle must be normalized to the interval (''-180deg'', ''180deg'']
 	(that is, greater than ''-180deg'', and less than or equal to ''180deg'').
 
@@ -3688,12 +3694,18 @@ Exponential  Functions: ''pow()'', ''sqrt()'', ''hypot()'', ''log()'', ''exp()''
 	both of which must resolve to <<number>>s,
 	and returns the result of raising A to the power of B,
 	returning the value as a <<number>>.
+	The input [=calculations=]
+	must have a [=consistent type=]
+	or else the function is invalid;
+	the result's type will be the [=consistent type=].
 
 	The <dfn lt="sqrt()">sqrt(A)</dfn> function
 	contains a single [=calculation=]
 	which must resolve to a <<number>>,
 	and returns the square root of the value
-	as a <<number>>.
+	as a <<number>>,
+	with the return type [=made consistent=]
+	with the input [=calculation’s=] type.
 	(''sqrt(X)'' and ''pow(X, .5)'' are basically equivalent,
 	differing only in some error-handling;
 	''sqrt()'' is a common enough function
@@ -4023,6 +4035,9 @@ Sign-Related Functions: ''abs()'', ''sign()''</h3>
 	+1 if A's numeric value is positive,
 	0⁺ if A's numeric value is 0⁺,
 	and 0⁻ if A's numeric value is 0⁻.
+	The return type is a <<number>>,
+	[=made consistent=]
+	with the input [=calculation’s=] type.
 
 	Note: Both of these functions operate on the fully simplified/resolved form of their arguments,
 	which may give unintuitive results at first glance.
@@ -4322,11 +4337,24 @@ Type Checking</h3>
 	</div>
 
 	<div algorithm>
-		Two or more calculations have a <dfn export local-lt="consistent">consistent type</dfn>
+		Two or more calculations have a <dfn export for=CSS local-lt="consistent">consistent type</dfn>
 		if [=add two types/adding the types=] doesn't result in failure.
 		The [=consistent type=] is the result of the type addition.
 	</div>
 
+	<div algorithm>
+		To <dfn export for=CSS lt="make a type consistent|make consistent|made consistent">make a type |base| consistent</dfn>
+		with another type |input|:
+
+		1. If both |base| and |input| have different non-null [=percent hints=],
+			they can't be made consistent.
+			Return failure.
+
+		2. Otherwise, set |base|’s [=percent hint=]
+			to |input|’s [=percent hint=],
+			and return |base|.
+	</div>
+
 	[=Math functions=] themselves have [=CSSNumericValue/types=],
 	according to their contained [=calculations=]: