Revert "[core] Widen signature of isTemplateDeclaration/isTemplateDec…

…larationOrInstance" (#5538)

Reverts #5527

.chronus/changes/revert-5527-witemple-msft-widen-template-detect-sig-2025-0-8-20-22-59.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: internal
+packages:
+  - "@typespec/compiler"
+---
+
+Revert "[core] Widen signature of isTemplateDeclaration/isTemplateDeclarationOrInstance"

.chronus/changes/witemple-msft-widen-template-detect-sig-2025-0-8-11-34-58.md

@@ -1,5 +1,5 @@
 ---
-changeKind: feature
+changeKind: internal
 packages:
   - "@typespec/compiler"
 ---

packages/compiler/src/core/type-utils.ts

@@ -120,7 +120,7 @@ export function isDeclaredType(type: Type): boolean {
  * Resolve if the type is a template type declaration(Non initialized template type).
  */
 export function isTemplateDeclaration(
-  type: Type,
+  type: TemplatedType,
 ): type is TemplatedType & { node: TemplateDeclarationNode } {
   if (type.node === undefined) {
     return false;
@@ -129,16 +129,14 @@ export function isTemplateDeclaration(
   return (
     node.templateParameters &&
     node.templateParameters.length > 0 &&
-    (type as TemplatedType).templateMapper === undefined
+    type.templateMapper === undefined
   );
 }
 
 /**
  * Resolve if the type was created from a template type or is a template type declaration.
  */
-export function isTemplateDeclarationOrInstance(
-  type: Type,
-): type is TemplatedType & { node: TemplateDeclarationNode } {
+export function isTemplateDeclarationOrInstance(type: TemplatedType): boolean {
   if (type.node === undefined) {
     return false;
   }