[clang-doc][NFC] Make test resilient to line changes (#119811)

This just reorganizes the test code, so its easy to use @line directives
in the test, and avoid needing to update all the line numbers when
making unrelated changes.

Author: ilovepi

clang-tools-extra/test/clang-doc/templates.cpp

@@ -6,22 +6,17 @@
 // RUN: cat %t/docs/index.yaml | FileCheck %s --check-prefix=YAML
 // RUN: rm -rf %t
 
-template<typename T, int U = 1>
-void function(T x) {}
-
-template<>
-void function<bool, 0>(bool x) {}
+// YAML: ---
+// YAML-NEXT: USR:             '{{([0-9A-F]{40})}}'
 
 template<class... T>
 void ParamPackFunction(T... args);
 
-// YAML: ---
-// YAML-NEXT: USR:             '{{([0-9A-F]{40})}}'
 // YAML-NEXT: ChildFunctions:
 // YAML-NEXT:  - USR:             '{{([0-9A-F]{40})}}'
 // YAML-NEXT:    Name:            'ParamPackFunction'
 // YAML-NEXT:    Location:
-// YAML-NEXT:      - LineNumber:      16
+// YAML-NEXT:      - LineNumber:      [[# @LINE - 6]]
 // YAML-NEXT:        Filename:        '{{.*}}'
 // YAML-NEXT:    Params:
 // YAML-NEXT:      - Type:
@@ -35,10 +30,14 @@ void ParamPackFunction(T... args);
 // YAML-NEXT:    Template:
 // YAML-NEXT:      Params:
 // YAML-NEXT:        - Contents:        'class... T'
+
+template<typename T, int U = 1>
+void function(T x) {}
+
 // YAML-NEXT:   - USR:             '{{([0-9A-F]{40})}}'
 // YAML-NEXT:     Name:            'function'
 // YAML-NEXT:     DefLocation:
-// YAML-NEXT:       LineNumber:      10
+// YAML-NEXT:       LineNumber:      [[# @LINE - 5]]
 // YAML-NEXT:       Filename:        '{{.*}}'
 // YAML-NEXT:     Params:
 // YAML-NEXT:       - Type:
@@ -53,10 +52,14 @@ void ParamPackFunction(T... args);
 // YAML-NEXT:       Params:
 // YAML-NEXT:         - Contents:        'typename T'
 // YAML-NEXT:         - Contents:        'int U = 1'
+
+template<>
+void function<bool, 0>(bool x) {}
+
 // YAML-NEXT:   - USR:             '{{([0-9A-F]{40})}}'
 // YAML-NEXT:     Name:            'function'
 // YAML-NEXT:     DefLocation:
-// YAML-NEXT:       LineNumber:      12
+// YAML-NEXT:       LineNumber:      [[# @LINE - 6]]
 // YAML-NEXT:       Filename:        '{{.*}}'
 // YAML-NEXT:     Params:
 // YAML-NEXT:       - Type:
@@ -74,3 +77,4 @@ void ParamPackFunction(T... args);
 // YAML-NEXT:           - Contents:        'bool'
 // YAML-NEXT:           - Contents:        '0'
 // YAML-NEXT: ...
+