new .redefine pragma for templates, warn on redefinition without it (#20211)

* test CI for template redefinitions

* adapt asyncmacro

* fix quote

* fix again

* try something else

* revert

* fix ioselectors_select, disable packages CI

* adapt more tests & simplify

* more

* more

* more

* rename to redefine, warn on implicit redefinition

* basic documentation [skip ci]

* Update compiler/lineinfos.nim

Co-authored-by: konsumlamm <44230978+konsumlamm@users.noreply.github.com>

Co-authored-by: konsumlamm <44230978+konsumlamm@users.noreply.github.com>

compiler/ast.nim

@@ -334,6 +334,7 @@ const
   sfEscapes* = sfProcvar              # param escapes
   sfBase* = sfDiscriminant
   sfCustomPragma* = sfRegister        # symbol is custom pragma template
+  sfTemplateRedefinition* = sfExportc # symbol is a redefinition of an earlier template
 
 const
   # getting ready for the future expr/stmt merge

compiler/condsyms.nim

@@ -140,3 +140,4 @@ proc initDefines*(symbols: StringTableRef) =
   defineSymbol("nimHasEffectsOf")
 
   defineSymbol("nimHasEnforceNoRaises")
+  defineSymbol("nimHasTemplateRedefinitionPragma")

compiler/lineinfos.nim

@@ -81,6 +81,7 @@ type
     warnCstringConv = "CStringConv",
     warnEffect = "Effect",
     warnCastSizes = "CastSizes"
+    warnTemplateRedefinition = "TemplateRedefinition",
     warnUser = "User",
     # hints
     hintSuccess = "Success", hintSuccessX = "SuccessX",
@@ -175,6 +176,7 @@ const
     warnCstringConv: "$1",
     warnEffect: "$1",
     warnCastSizes: "$1",
+    warnTemplateRedefinition: "template '$1' is implicitly redefined, consider adding an explicit .redefine pragma",
     warnUser: "$1",
     hintSuccess: "operation successful: $#",
     # keep in sync with `testament.isSuccess`

compiler/pragmas.nim

@@ -38,7 +38,7 @@ const
   converterPragmas* = procPragmas
   methodPragmas* = procPragmas+{wBase}-{wImportCpp}
   templatePragmas* = {wDeprecated, wError, wGensym, wInject, wDirty,
-    wDelegator, wExportNims, wUsed, wPragma}
+    wDelegator, wExportNims, wUsed, wPragma, wRedefine}
   macroPragmas* = declPragmas + {FirstCallConv..LastCallConv,
     wMagic, wNoSideEffect, wCompilerProc, wNonReloadable, wCore,
     wDiscardable, wGensym, wInject, wDelegator}
@@ -870,6 +870,9 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: var int,
       of wDirty:
         if sym.kind == skTemplate: incl(sym.flags, sfDirty)
         else: invalidPragma(c, it)
+      of wRedefine:
+        if sym.kind == skTemplate: incl(sym.flags, sfTemplateRedefinition)
+        else: invalidPragma(c, it)
       of wImportCpp:
         processImportCpp(c, sym, getOptionalStr(c, it, "$1"), it.info)
       of wCppNonPod:

compiler/semexprs.nim

@@ -2112,10 +2112,12 @@ proc semQuoteAst(c: PContext, n: PNode): PNode =
   ids[0] = newAnonSym(c, skParam, n.info).newSymNode
   processQuotations(c, quotedBlock, op, quotes, ids)
 
+  let dummyTemplateSym = newAnonSym(c, skTemplate, n.info)
+  incl(dummyTemplateSym.flags, sfTemplateRedefinition)
   var dummyTemplate = newProcNode(
     nkTemplateDef, quotedBlock.info, body = quotedBlock,
     params = c.graph.emptyNode,
-    name = newAnonSym(c, skTemplate, n.info).newSymNode,
+    name = dummyTemplateSym.newSymNode,
               pattern = c.graph.emptyNode, genericParams = c.graph.emptyNode,
               pragmas = c.graph.emptyNode, exceptions = c.graph.emptyNode)
 

compiler/semtempl.nim

@@ -691,6 +691,9 @@ proc semTemplateDef(c: PContext, n: PNode): PNode =
   if proto == nil:
     addInterfaceOverloadableSymAt(c, c.currentScope, s)
   elif not comesFromShadowscope:
+    if {sfTemplateRedefinition, sfGenSym} * s.flags == {}:
+      #wrongRedefinition(c, n.info, proto.name.s, proto.info)
+      message(c.config, n.info, warnTemplateRedefinition, s.name.s)
     symTabReplace(c.currentScope.symbols, proto, s)
   if n[patternPos].kind != nkEmpty:
     c.patterns.add(s)

compiler/wordrecg.nim

@@ -87,6 +87,7 @@ type
     wGlobal = "global", wCodegenDecl = "codegenDecl", wUnchecked = "unchecked",
     wGuard = "guard", wLocks = "locks", wPartial = "partial", wExplain = "explain",
     wLiftLocals = "liftlocals", wEnforceNoRaises = "enforceNoRaises",
+    wRedefine = "redefine",
 
     wAuto = "auto", wBool = "bool", wCatch = "catch", wChar = "char",
     wClass = "class", wCompl = "compl", wConstCast = "const_cast", wDefault = "default",