[functions] Validate defaults against their type

The spec was recently clarified to make @function rules
with "mistyped" defaults invalid. For example, the following
is now invalid, because the default given for --arg doesn't match
the type given for --arg:

  @function --foo(--arg <color>: 10px) { /* ... */ }

w3c/csswg-drafts#12243

Fixed: 423673310
Change-Id: I3239b573ece22bb48746a496758d53f57ac00b70
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6632858
Commit-Queue: Anders Hartvoll Ruud <[email protected]>
Reviewed-by: Steinar H Gunderson <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1472448}

Author: andruud

css/css-mixins/at-function-parsing.html

@@ -60,6 +60,7 @@
 
   // Defaults.
   test_valid_prelude('@function --foo(--x : 10px)');
+  test_valid_prelude('@function --foo(--x type(*): 10px)');
   test_valid_prelude('@function --foo(--x <length>: 10px)');
   test_valid_prelude('@function --foo(--x <length>: 10px, --y)');
   test_valid_prelude('@function --foo(--x, --y <length>: 10px)');
@@ -69,11 +70,16 @@
   // a default, even though there's no way to actually call --foo()
   // with just --y:
   test_valid_prelude('@function --foo(--x:1px, --y, --z:2px)');
-  // The value does not have to match the type during @function parsing:
-  test_valid_prelude('@function --foo(--x <angle>: 10px)');
 
   test_invalid_prelude('@function --foo(--x: 10px !important)');
 
+  // Default type mismatch.
+  test_invalid_prelude('@function --foo(--x <length>: 10deg)');
+  test_invalid_prelude('@function --foo(--x <angle>: 10px)');
+  test_invalid_prelude('@function --foo(--x <color>: 10px)');
+  test_invalid_prelude('@function --foo(--x type(<color>+): red 5)');
+  test_invalid_prelude('@function --foo(--x type(auto | none): thing)');
+
   // Lists.
   test_valid_prelude('@function --foo(--x <length>#)');
   test_valid_prelude('@function --foo(--x <length>+)');