Revert "Remove dead code from sem/procfind"

This reverts commit fb45aec.

compiler/sem/procfind.nim

@@ -28,6 +28,22 @@ import
 from compiler/ast/reports_sem import reportSym
 from compiler/ast/report_enums import ReportKind
 
+proc equalGenericParams(procA, procB: PNode): bool {.used.} =
+  # currently unused, but might be used again
+  if procA.len != procB.len: return false
+  for i in 0..<procA.len:
+    if procA[i].kind != nkSym:
+      return false
+    if procB[i].kind != nkSym:
+      return false
+    let a = procA[i].sym
+    let b = procB[i].sym
+    if a.name.id != b.name.id or
+        not sameTypeOrNil(a.typ, b.typ, {ExactTypeDescValues}): return
+    if a.ast != nil and b.ast != nil:
+      if not exprStructuralEquivalent(a.ast, b.ast): return
+  result = true
+
 proc searchForProcAux(c: PContext, scope: PScope, fn: PSym): PSym =
   var it: TIdentIter
   result = initIdentIter(it, scope.symbols, fn.name)
@@ -56,3 +72,29 @@ proc searchForProc*(c: PContext, scope: PScope, fn: PSym): tuple[proto: PSym, co
     result.proto = searchForProcAux(c, scope, fn)
     result.comesFromShadowScope = true
 
+when false:
+  proc paramsFitBorrow(child, parent: PNode): bool =
+    result = false
+    if child.len == parent.len:
+      for i in 1..<child.len:
+        var m = child[i].sym
+        var n = parent[i].sym
+        assert((m.kind == skParam) and (n.kind == skParam))
+        if not compareTypes(m.typ, n.typ, dcEqOrDistinctOf): return
+      if not compareTypes(child[0].typ, parent[0].typ,
+                          dcEqOrDistinctOf): return
+      result = true
+
+  proc searchForBorrowProc*(c: PContext, startScope: PScope, fn: PSym): PSym =
+    # Searches for the fn in the symbol table. If the parameter lists are suitable
+    # for borrowing the sym in the symbol table is returned, else nil.
+    var it: TIdentIter
+    for scope in walkScopes(startScope):
+      result = initIdentIter(it, scope.symbols, fn.Name)
+      while result != nil:
+        # watchout! result must not be the same as fn!
+        if (result.Kind == fn.kind) and (result.id != fn.id):
+          if equalGenericParams(result.ast[genericParamsPos],
+                                fn.ast[genericParamsPos]):
+            if paramsFitBorrow(fn.typ.n, result.typ.n): return
+        result = NextIdentIter(it, scope.symbols)