Add associative map constraints and range refinement

crates/decodal-language-service/src/completion.rs

@@ -222,6 +222,7 @@ fn builtin_items() -> Vec<CompletionItem> {
         ("match", CompletionKind::Keyword, "pattern matching", 5),
         ("import", CompletionKind::Keyword, "load a module", 5),
         ("default", CompletionKind::Keyword, "fallback value", 0),
+        ("as", CompletionKind::Keyword, "refine narrower as wider", 0),
         ("true", CompletionKind::Constant, "Bool", 0),
         ("false", CompletionKind::Constant, "Bool", 0),
         ("String", CompletionKind::Type, "string constraint", 5),
@@ -276,6 +277,10 @@ fn fields_from_host_value(value: &HostValue) -> FieldTree {
             default: Some(value),
             ..
         }
+        | HostValue::MapConstraint {
+            default: Some(value),
+            ..
+        }
         | HostValue::Abstract {
             default: Some(value),
             ..