Only showing traces with >1 entries

Author: EnzeXing

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

@@ -1759,24 +1759,31 @@ class Objects:
       if cls.isAllOf(Flags.JavaInterface) then Bottom
       else evalType(tref.prefix, thisV, klass, elideObjectAccess = cls.isStatic)
 
+  def printTraceWhenMultiple(trace: Trace)(using Context): String =
+    if trace.toVector.size > 1 then
+      Trace.buildStacktrace(trace, "The mutable state is created through: " + System.lineSeparator())
+    else ""
+
   val mutateErrorSet: mutable.Set[(ClassSymbol, ClassSymbol)] = mutable.Set.empty
   def errorMutateOtherStaticObject(currentObj: ClassSymbol, addr: Heap.Addr)(using Trace, Context) =
     val otherObj = addr.owner
+    val addr_trace = addr.getTrace
     if mutateErrorSet.add((currentObj, otherObj)) then
       val msg =
         s"Mutating ${otherObj.show} during initialization of ${currentObj.show}.\n" +
         "Mutating other static objects during the initialization of one static object is forbidden. " + Trace.show +
-        "The mutable state is created through: " + Trace.show(using addr.getTrace)
+        printTraceWhenMultiple(addr_trace)
 
       report.warning(msg, Trace.position)
 
   val readErrorSet: mutable.Set[(ClassSymbol, ClassSymbol)] = mutable.Set.empty
   def errorReadOtherStaticObject(currentObj: ClassSymbol, addr: Heap.Addr)(using Trace, Context) =
     val otherObj = addr.owner
+    val addr_trace = addr.getTrace
     if readErrorSet.add((currentObj, otherObj)) then
       val msg =
         "Reading mutable state of " + otherObj.show + " during initialization of " + currentObj.show + ".\n" +
         "Reading mutable state of other static objects is forbidden as it breaks initialization-time irrelevance. " + Trace.show +
-        "The mutable state is created through: " + Trace.show(using addr.getTrace)
+        printTraceWhenMultiple(addr_trace)
 
       report.warning(msg, Trace.position)

tests/init-global/warn/global-cycle5.check

@@ -7,6 +7,3 @@
    |│   ^
    |└── val b: Int = A.a.foo() // warn	[ global-cycle5.scala:10 ]
    |                 ^^^
-   |The mutable state is created through: Calling trace:
-   |└── object A {	[ global-cycle5.scala:5 ]
-   |    ^

tests/init-global/warn/global-irrelevance1.check

@@ -7,6 +7,3 @@
   |│   ^
   |└── var y = A.x * 2 // warn	[ global-irrelevance1.scala:5 ]
   |            ^^^
-  |The mutable state is created through: Calling trace:
-  |└── object A:	[ global-irrelevance1.scala:1 ]
-  |    ^

tests/init-global/warn/global-irrelevance2.check

@@ -11,6 +11,3 @@
   |  │   ^
   |  └── A.x =  b * 2 // warn	[ global-irrelevance2.scala:5 ]
   |      ^^^^^^^^^^^^
-  |  The mutable state is created through: Calling trace:
-  |  └── object A:	[ global-irrelevance2.scala:1 ]
-  |      ^

tests/init-global/warn/global-irrelevance3.check

@@ -9,4 +9,3 @@
   |│           ^^^^^^^
   |└── (() => x) // warn	[ global-irrelevance3.scala:9 ]
   |           ^
-  |The mutable state is created through: 

tests/init-global/warn/global-irrelevance4.check

@@ -9,4 +9,3 @@
   |       │   ^^^^^^^^^
   |       └── (y => x = y), // warn	[ global-irrelevance4.scala:8 ]
   |            ^^^^^^^^^^
-  |       The mutable state is created through: 

tests/init-global/warn/global-irrelevance5.check

@@ -7,7 +7,7 @@
   |│   ^
   |└── var y = A.array(0) * 2 // warn	[ global-irrelevance5.scala:6 ]
   |            ^^^^^^^^^^
-  |The mutable state is created through: Calling trace:
+  |The mutable state is created through: 
   |├── object A:	[ global-irrelevance5.scala:1 ]
   |│   ^
   |└── val array: Array[Int] = new Array(1)	[ global-irrelevance5.scala:2 ]

tests/init-global/warn/global-irrelevance6.check

@@ -7,7 +7,7 @@
   |│   ^
   |└── var y = A.array(0).foo() * 2 // warn	[ global-irrelevance6.scala:9 ]
   |            ^^^^^^^^^^
-  |The mutable state is created through: Calling trace:
+  |The mutable state is created through: 
   |├── object A:	[ global-irrelevance6.scala:4 ]
   |│   ^
   |└── val array: Array[Box] = new Array(1)	[ global-irrelevance6.scala:5 ]

tests/init-global/warn/global-irrelevance7.check

@@ -7,7 +7,7 @@
    |│   ^
    |└── var y = A.array(0).foo() * 2 // warn	[ global-irrelevance7.scala:10 ]
    |            ^^^^^^^^^^
-   |The mutable state is created through: Calling trace:
+   |The mutable state is created through: 
    |├── object A:	[ global-irrelevance7.scala:4 ]
    |│   ^
    |└── val array: Array[Box] = new Array(1)	[ global-irrelevance7.scala:5 ]

tests/init-global/warn/mutable-array.check

@@ -7,7 +7,7 @@
   |│   ^
   |└── val x: Int = box.value // warn	[ mutable-array.scala:8 ]
   |                 ^^^^^^^^^
-  |The mutable state is created through: Calling trace:
+  |The mutable state is created through: 
   |├── object A:	[ mutable-array.scala:1 ]
   |│   ^
   |├── val box: Box = new Box(0)	[ mutable-array.scala:3 ]