ORC: support for custom =trace procs (#18459)

* ORC: support custom =trace procs (WIP)
* Update tests/arc/tcustomtrace.nim

Co-authored-by: Clyybber <darkmine956@gmail.com>

* =trace is now documented and seems to work
* make test green

Co-authored-by: Clyybber <darkmine956@gmail.com>

8 files changed, 35 insertions, 8 deletions

diff --git a/compiler/ast.nim b/compiler/ast.nim
index 26050426a..f96e464af 100644
--- a/compiler/ast.nim
+++ b/compiler/ast.nim
@@ -667,7 +667,7 @@ type
     mIsPartOf, mAstToStr, mParallel,
     mSwap, mIsNil, mArrToSeq,
     mNewString, mNewStringOfCap, mParseBiggestFloat,
-    mMove, mWasMoved, mDestroy,
+    mMove, mWasMoved, mDestroy, mTrace,
     mDefault, mUnown, mIsolate, mAccessEnv, mReset,
     mArray, mOpenArray, mRange, mSet, mSeq, mVarargs,
     mRef, mPtr, mVar, mDistinct, mVoid, mTuple,
diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index c07ddf1db..09326ceeb 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -2422,6 +2422,7 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
   of mDestroy: genDestroy(p, e)
   of mAccessEnv: unaryExpr(p, e, d, "$1.ClE_0")
   of mSlice: genSlice(p, e, d)
+  of mTrace: discard "no code to generate"
   else:
     when defined(debugMagics):
       echo p.prc.name.s, " ", p.prc.id, " ", p.prc.flags, " ", p.prc.ast[genericParamsPos].kind
diff --git a/compiler/condsyms.nim b/compiler/condsyms.nim
index b3f8465f0..33cd1818b 100644
--- a/compiler/condsyms.nim
+++ b/compiler/condsyms.nim
@@ -136,3 +136,4 @@ proc initDefines*(symbols: StringTableRef) =
   defineSymbol("nimHasTypeofVoid")
   defineSymbol("nimHasDragonBox")
   defineSymbol("nimHasHintAll")
+  defineSymbol("nimHasTrace")
diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index a9339c7fd..82fba02a6 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -2079,7 +2079,7 @@ proc genMagic(p: PProc, n: PNode, r: var TCompRes) =
       gen(p, n[1], x)
       useMagic(p, "nimCopy")
       r.res = "nimCopy(null, $1, $2)" % [x.rdLoc, genTypeInfo(p, n.typ)]
-  of mDestroy: discard "ignore calls to the default destructor"
+  of mDestroy, mTrace: discard "ignore calls to the default destructor"
   of mOrd: genOrd(p, n, r)
   of mLengthStr, mLengthSeq, mLengthOpenArray, mLengthArray:
     var x: TCompRes
diff --git a/compiler/liftdestructors.nim b/compiler/liftdestructors.nim
index 1824557e6..b2b70edee 100644
--- a/compiler/liftdestructors.nim
+++ b/compiler/liftdestructors.nim
@@ -416,11 +416,23 @@ proc considerUserDefinedOp(c: var TLiftCtx; t: PType; body, x, y: PNode): bool =
       body.add destructorCall(c, op, x)
       result = true
     #result = addDestructorCall(c, t, body, x)
-  of attachedAsgn, attachedSink, attachedTrace:
+  of attachedAsgn, attachedSink:
     var op = getAttachedOp(c.g, t, c.kind)
     result = considerAsgnOrSink(c, t, body, x, y, op)
     if op != nil:
       setAttachedOp(c.g, c.idgen.module, t, c.kind, op)
+  of attachedTrace:
+    var op = getAttachedOp(c.g, t, c.kind)
+    if op != nil and sfOverriden in op.flags:
+      if op.ast.isGenericRoutine:
+        # patch generic =trace:
+        op = instantiateGeneric(c, op, t, t.typeInst)
+        setAttachedOp(c.g, c.idgen.module, t, c.kind, op)
+
+    result = considerAsgnOrSink(c, t, body, x, y, op)
+    if op != nil:
+      setAttachedOp(c.g, c.idgen.module, t, c.kind, op)
+
   of attachedDeepCopy:
     let op = getAttachedOp(c.g, t, attachedDeepCopy)
     if op != nil:
@@ -1065,7 +1077,7 @@ proc createTypeBoundOps(g: ModuleGraph; c: PContext; orig: PType; info: TLineInf
   # 4. We have a custom destructor.
   # 5. We have a (custom) generic destructor.
 
-  # we do not generate '=trace' nor '=dispose' procs if we
+  # we do not generate '=trace' procs if we
   # have the cycle detection disabled, saves code size.
   let lastAttached = if g.config.selectedGC == gcOrc: attachedTrace
                      else: attachedSink
diff --git a/compiler/semmagic.nim b/compiler/semmagic.nim
index d3f26e630..04f4c4729 100644
--- a/compiler/semmagic.nim
+++ b/compiler/semmagic.nim
@@ -551,6 +551,12 @@ proc magicsAfterOverloadResolution(c: PContext, n: PNode,
     let op = getAttachedOp(c.graph, t, attachedDestructor)
     if op != nil:
       result[0] = newSymNode(op)
+  of mTrace:
+    result = n
+    let t = n[1].typ.skipTypes(abstractVar)
+    let op = getAttachedOp(c.graph, t, attachedTrace)
+    if op != nil:
+      result[0] = newSymNode(op)
   of mUnown:
     result = semUnown(c, n)
   of mExists, mForall:
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index c3402aee3..fd2f8a1d9 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -1649,6 +1649,8 @@ proc bindTypeHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp) =
   var noError = false
   let cond = if op == attachedDestructor:
                t.len == 2 and t[0] == nil and t[1].kind == tyVar
+             elif op == attachedTrace:
+               t.len == 3 and t[0] == nil and t[1].kind == tyVar and t[2].kind == tyPointer
              else:
                t.len >= 2 and t[0] == nil
 
@@ -1673,8 +1675,12 @@ proc bindTypeHook(c: PContext; s: PSym; n: PNode; op: TTypeAttachedOp) =
         localError(c.config, n.info, errGenerated,
           "type bound operation `" & s.name.s & "` can be defined only in the same module with its type (" & obj.typeToString() & ")")
   if not noError and sfSystemModule notin s.owner.flags:
-    localError(c.config, n.info, errGenerated,
-      "signature for '" & s.name.s & "' must be proc[T: object](x: var T)")
+    if op == attachedTrace:
+      localError(c.config, n.info, errGenerated,
+        "signature for '=trace' must be proc[T: object](x: var T; env: pointer)")
+    else:
+      localError(c.config, n.info, errGenerated,
+        "signature for '" & s.name.s & "' must be proc[T: object](x: var T)")
   incl(s.flags, sfUsed)
   incl(s.flags, sfOverriden)
 
@@ -1752,7 +1758,8 @@ proc semOverride(c: PContext, s: PSym, n: PNode) =
       localError(c.config, n.info, errGenerated,
                 "signature for '" & s.name.s & "' must be proc[T: object](x: var T; y: T)")
   of "=trace":
-    bindTypeHook(c, s, n, attachedTrace)
+    if s.magic != mTrace:
+      bindTypeHook(c, s, n, attachedTrace)
   else:
     if sfOverriden in s.flags:
       localError(c.config, n.info, errGenerated,
diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim
index 14f9e0b30..e5e4a854e 100644
--- a/compiler/vmgen.nim
+++ b/compiler/vmgen.nim
@@ -1362,7 +1362,7 @@ proc genMagic(c: PCtx; n: PNode; dest: var TDest; m: TMagic) =
     globalError(c.config, n.info, sizeOfLikeMsg("offsetof"))
   of mRunnableExamples:
     discard "just ignore any call to runnableExamples"
-  of mDestroy: discard "ignore calls to the default destructor"
+  of mDestroy, mTrace: discard "ignore calls to the default destructor"
   of mMove:
     let arg = n[1]
     let a = c.genx(arg)