fixes #2286

compiler/lowerings.nim

@@ -203,6 +203,17 @@ proc flowVarKind(t: PType): TFlowVarKind =
   elif containsGarbageCollectedRef(t): fvInvalid
   else: fvBlob
 
+proc typeNeedsNoDeepCopy(t: PType): bool =
+  var t = t.skipTypes(abstractInst)
+  # for the tconvexhull example (and others) we're a bit lax here and pretend
+  # seqs and strings are *by value* only and 'shallow' doesn't exist!
+  if t.kind == tyString: return true
+  # note that seq[T] is fine, but 'var seq[T]' is not, so we need to skip 'var'
+  # for the stricter check and likewise we can skip 'seq' for a less
+  # strict check:
+  if t.kind in {tyVar, tySequence}: t = t.sons[0]
+  result = not containsGarbageCollectedRef(t)
+
 proc addLocalVar(varSection, varInit: PNode; owner: PSym; typ: PType;
                  v: PNode; useShallowCopy=false): PSym =
   result = newSym(skTemp, getIdent(genPrefix), owner, varSection.info)
@@ -215,7 +226,7 @@ proc addLocalVar(varSection, varInit: PNode; owner: PSym; typ: PType;
   vpart.sons[2] = if varInit.isNil: v else: ast.emptyNode
   varSection.add vpart
   if varInit != nil:
-    if useShallowCopy:
+    if useShallowCopy and typeNeedsNoDeepCopy(typ):
       varInit.add newFastAsgnStmt(newSymNode(result), v)
     else:
       let deepCopyCall = newNodeI(nkCall, varInit.info, 3)

tests/parallel/tconvexhull.nim

@@ -6,7 +6,7 @@ true
 true
 true'''
 
-ccodeCheck: "!'deepcopy('"
+ccodeCheck: "\\i ! @'deepCopy(' .*"
 """
 
 # parallel convex hull for Nim bigbreak

tests/parallel/tmissing_deepcopy.nim

@@ -0,0 +1,40 @@
+discard """
+  ccodeCheck: "\\i @'deepCopy(' .*"
+"""
+
+# bug #2286
+
+import threadPool
+
+type
+  Person = ref object
+    name: string
+    friend: Person
+
+var
+  people: seq[Person] = @[]
+
+proc newPerson(name:string): Person =
+  result.new()
+  result.name = name
+
+proc greet(p:Person) =
+  p.friend.name &= "-MUT" # this line crashes the program
+  echo "Person {",
+    " name:", p.name, "(", cast[int](addr p.name),"),",
+    " friend:", p.friend.name, "(", cast[int](addr p.friend.name),") }"
+
+proc setup =
+  for i in 0 .. <20:
+    people.add newPerson("Person" & $(i + 1))
+  for i in 0 .. <20:
+    people[i].friend = people[19-i]
+
+proc update =
+  parallel:
+    for i in 0 .. people.high:
+      spawn people[i].greet()
+
+when isMainModule:
+  setup()
+  update()

tests/testament/tester.nim

@@ -148,7 +148,11 @@ proc codegenCheck(test: TTest, check: string, given: var TSpec) =
     let genFile = generatedFile(path, name, test.target)
     echo genFile
     let contents = readFile(genFile).string
-    if contents.find(check.peg) < 0:
+    if check[0] == '\\':
+      # little hack to get 'match' support:
+      if not contents.match(check.peg):
+        given.err = reCodegenFailure
+    elif contents.find(check.peg) < 0:
       given.err = reCodegenFailure
   except ValueError:
     given.err = reInvalidPeg