[css-values-4] Rather than clumsily indirecting thru TypedOM's type-creator algo, just inline it using the concepts I have on hand. Remove more redundant type-determining text. Move notes to the end of the type-determining section (retaining their relative place to the old type-determining text). Now that 8.1.2 is just intro text, remove the 8.1.2.1 subheading and just promote it all up.

Author: tabatkins

css-values-4/Overview.bs

@@ -1603,8 +1603,11 @@ Mathematical Expressions: ''calc()'', ''min()'', and ''max()''</h3>
 	<<frequency>>,
 	<<angle>>,
 	<<time>>,
+	<<flex>>,
+	<<resolution>>,
 	<<percentage>>,
-	or <<number>>
+	<<number>>,
+	or <<integer>>
 	values are allowed.
 	Components of a [=math function=] can be literal values,
 	other [=math functions=],
@@ -1700,7 +1703,7 @@ Type Checking</h4>
 	A [=math function=] can be many possible types,
 	such as <<length>>, <<number>>, etc.,
 	depending on the expression it contains,
-	as defined in [[#type-checking-exprs]].
+	as defined below.
 	It can be used anywhere a value of that type is allowed.
 
 	<div class=example>
@@ -1715,42 +1718,6 @@ Type Checking</h4>
 	(It gets rounded to the nearest integer,
 	as specified in [[#calc-range]].)
 
-	Note: Because <<number-token>>s are always interpreted as <<number>>s or <<integer>>s,
-	"unitless 0" <<length>>s aren't supported in [=math functions=].
-	That is, ''width: calc(0 + 5px);'' is invalid,
-	because it's trying to add a <<number>> to a <<length>>,
-	even though both ''width: 0;''
-	and ''width: 5px;''
-	are valid.
-
-	If percentages are accepted in the context in which the expression is placed,
-	and they are defined to be relative to another type besides <<number>>,
-	a <<percentage-token>> is treated as that type.
-	For example, in the 'width' property, percentages have the <<length>> type.
-	A percentage only has the <<percentage>> type if in that context
-	<<percentage>> values are not used-value compatible with any other type.
-	If percentages are not normally allowed in place of the ''calc()'',
-	then a ''calc()'' expression containing percentages is invalid in that context.
-
-	Note: Note that <<percentage>>s relative to <<number>>s,
-	such as in 'opacity',
-	are not allowed in ''calc()''.
-	Allowing this would cause significant problems with "unit algebra"
-	(allowing multiplication/division of <<dimension>>s),
-	and in every case so far,
-	doesn't provide any new functionality.
-	(For example, ''opacity: 25%'' is identical to ''opacity: .25'';
-	it's just a trivial syntax transform.)
-
-	Note: Altho there are a few properties in which a bare <<number>>
-	becomes a <<length>> at used-value time
-	(specifically, 'line-height' and 'tab-size'),
-	<<number>>s never become "length-like" in ''calc()''.
-	They always stay as <<number>>s.
-
-<h5 id="type-checking-exprs">
-Type-Checking Expressions</h5>
-
 	Operators form sub-expressions, which gain types based on their arguments.
 	In previous versions of this specification,
 	multiplication and division were limited in what arguments they could take,
@@ -1784,18 +1751,38 @@ Type-Checking Expressions</h5>
 		the entire [=math function=] is invalid.
 		Otherwise, the sub-expression's [=CSSNumericValue/type=] is the returned type.
 
-	* The [=CSSNumericValue/type=] of a literal
-		is the result of [=creating a type=]
-		from the literal's unit,
-		if it's a <<dimension>>,
-		or from "number"
-		if it's a <<number>>.
-		For <<percentage>>s,
-		if they're relative to another type
-		(as defined in the previous section),
-		their type is [=create a type|created=]
-		from the [=canonical unit=] of the type they're resolved to;
-		otherwise it's [=create a type|created=] from "percentage".
+	* Anything else is a terminal value,
+		whose [=CSSNumericValue/type=] is determined based on its CSS type:
+
+		<dl class=switch>
+			: <<number>>
+			: <<integer>>
+			:: [=CSSNumericValue/type=] is «[ ]» (empty map)
+			: <<length>>
+			:: [=CSSNumericValue/type=] is «[ "length" → 1 ]»
+			: <<angle>>
+			:: [=CSSNumericValue/type=] is «[ "angle" → 1 ]»
+			: <<time>>
+			:: [=CSSNumericValue/type=] is «[ "time" → 1 ]»
+			: <<frequency>>
+			:: [=CSSNumericValue/type=] is «[ "frequency" → 1 ]»
+			: <<resolution>>
+			:: [=CSSNumericValue/type=] is «[ "resolution" → 1 ]»
+			: <<flex>>
+			:: [=CSSNumericValue/type=] is «[ "flex" → 1 ]»
+			: <<percentage>>
+			::
+				If, in the context in which the [=math function=] is placed,
+				<<percentage>>s are resolved relative to another type of value
+				(such as in 'width', where <<percentage>> is resolved against a <<length>>),
+				and that other type is <em>not</em> <<number>>,
+				the [=CSSNumericValue/type=] is determined as the other type.
+
+				Otherwise,
+				[=CSSNumericValue/type=] is «[ "percent" → 1 ]».
+			: anything else
+			:: The [=math function=] is invalid.
+	       </dl>
 
 	* The [=CSSNumericValue/type=] of a ''calc()'' expression
 		is the [=CSSNumericValue/type=] of its contained expression.
@@ -1827,6 +1814,34 @@ Type-Checking Expressions</h5>
 	For example, ''calc(5px - 5px + 10s)'' and ''calc(0 * 5px + 10s)'' are both invalid
 	due to the attempt to add a length and a time.
 
+	Note: Note that <<percentage>>s relative to <<number>>s,
+	such as in 'opacity',
+	are not <em>combinable</em> with those numbers--
+	''opacity: calc(.25 + 25%)'' is invalid.
+	Allowing this would cause significant problems with "unit algebra"
+	(allowing multiplication/division of <<dimension>>s),
+	and in every case so far,
+	doesn't provide any new functionality.
+	(For example, ''opacity: 25%'' is identical to ''opacity: .25'';
+	it's just a trivial syntax transform.)
+	You can still perform other operations with them,
+	such as ''opacity: calc(100% / 3);'',
+	which is valid.
+
+	Note: Because <<number-token>>s are always interpreted as <<number>>s or <<integer>>s,
+	"unitless 0" <<length>>s aren't supported in [=math functions=].
+	That is, ''width: calc(0 + 5px);'' is invalid,
+	because it's trying to add a <<number>> to a <<length>>,
+	even though both ''width: 0;''
+	and ''width: 5px;''
+	are valid.
+
+	Note: Altho there are a few properties in which a bare <<number>>
+	becomes a <<length>> at used-value time
+	(specifically, 'line-height' and 'tab-size'),
+	<<number>>s never become "length-like" in ''calc()''.
+	They always stay as <<number>>s.
+
 <h4 id='calc-computed-value'>
 Computed Value</h4>