Update trace format for consistency

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/init/Trace.scala

@@ -61,12 +61,13 @@ object Trace:
       val line =
         if pos.exists then
           val loc = pos.source.file.name + ":" + (pos.line + 1)
-          if hasSource then
-            val code = SyntaxHighlighting.highlight(pos.lineContent.trim)
-            i"$code\t[ $loc ]"
-          else
-            loc
+          val code =
+            if hasSource then
+              SyntaxHighlighting.highlight(pos.lineContent.trim)
+            else
+              "(no source)"
 
+          i"$code\t[ $loc ]"
         else
           tree match
             case defDef: DefTree =>

tests/init-global/special/tastySource/B.check

@@ -5,8 +5,8 @@
   |Reading mutable state of other static objects is forbidden as it breaks initialization-time irrelevance. Calling trace:
   |├── object B:	[ B.scala:1 ]
   |│   ^
-  |├── A.scala:2
-  |├── A.scala:4
+  |├── (no source)	[ A.scala:2 ]
+  |├── (no source)	[ A.scala:4 ]
   |├── var y = A.foo(bar) * 2	[ B.scala:2 ]
   |│                 ^^^
   |└── def bar = C.n * 3      // warn	[ B.scala:4 ]