fixes #11225; generic sandwich problems; [backport:1.2]

compiler/ccgexprs.nim

@@ -2906,6 +2906,7 @@ proc expr(p: BProc, n: PNode, d: var TLoc) =
     inc p.splitDecls
     genGotoState(p, n)
   of nkBreakState: genBreakState(p, n, d)
+  of nkMixinStmt: discard
   else: internalError(p.config, n.info, "expr(" & $n.kind & "); unknown node kind")
 
 proc genNamedConstExpr(p: BProc, n: PNode; isConst: bool): Rope =

compiler/cgen.nim

@@ -860,7 +860,7 @@ proc containsResult(n: PNode): bool =
     for i in 0..<n.safeLen:
       if containsResult(n[i]): return true
 
-const harmless = {nkConstSection, nkTypeSection, nkEmpty, nkCommentStmt, nkTemplateDef, nkMacroDef} +
+const harmless = {nkConstSection, nkTypeSection, nkEmpty, nkCommentStmt, nkTemplateDef, nkMacroDef, nkMixinStmt} +
                   declarativeDefs
 
 proc easyResultAsgn(n: PNode): PNode =

compiler/closureiters.nim

@@ -157,7 +157,7 @@ type
 
 const
   nkSkip = {nkEmpty..nkNilLit, nkTemplateDef, nkTypeSection, nkStaticStmt,
-            nkCommentStmt} + procDefs
+            nkCommentStmt, nkMixinStmt} + procDefs
 
 proc newStateAccess(ctx: var Ctx): PNode =
   if ctx.stateVarSym.isNil:

compiler/injectdestructors.nim

@@ -890,7 +890,7 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode): PNode =
     of nkNone..nkNilLit, nkTypeSection, nkProcDef, nkConverterDef,
        nkMethodDef, nkIteratorDef, nkMacroDef, nkTemplateDef, nkLambda, nkDo,
        nkFuncDef, nkConstSection, nkConstDef, nkIncludeStmt, nkImportStmt,
-       nkExportStmt, nkPragma, nkCommentStmt, nkBreakState, nkTypeOfExpr:
+       nkExportStmt, nkPragma, nkCommentStmt, nkBreakState, nkTypeOfExpr, nkMixinStmt:
       result = n
 
     of nkStringToCString, nkCStringToString, nkChckRangeF, nkChckRange64, nkChckRange, nkPragmaBlock:

compiler/jsgen.nim

@@ -2626,7 +2626,7 @@ proc gen(p: PProc, n: PNode, r: var TCompRes) =
   of nkRaiseStmt: genRaiseStmt(p, n)
   of nkTypeSection, nkCommentStmt, nkIncludeStmt,
      nkImportStmt, nkImportExceptStmt, nkExportStmt, nkExportExceptStmt,
-     nkFromStmt, nkTemplateDef, nkMacroDef, nkStaticStmt: discard
+     nkFromStmt, nkTemplateDef, nkMacroDef, nkStaticStmt, nkMixinStmt: discard
   of nkIteratorDef:
     if n[0].sym.typ.callConv == TCallingConvention.ccClosure:
       globalError(p.config, n.info, "Closure iterators are not supported by JS backend!")

compiler/lambdalifting.nim

@@ -497,7 +497,7 @@ proc detectCapturedVars(n: PNode; owner: PSym; c: var DetectionPass) =
           w = up
   of nkEmpty..pred(nkSym), succ(nkSym)..nkNilLit,
      nkTemplateDef, nkTypeSection, nkProcDef, nkMethodDef,
-     nkConverterDef, nkMacroDef, nkFuncDef, nkCommentStmt, nkTypeOfExpr:
+     nkConverterDef, nkMacroDef, nkFuncDef, nkCommentStmt, nkTypeOfExpr, nkMixinStmt:
     discard
   of nkLambdaKinds, nkIteratorDef:
     if n.typ != nil:
@@ -752,7 +752,7 @@ proc liftCapturedVars(n: PNode; owner: PSym; d: var DetectionPass;
         result = accessViaEnvVar(n, owner, d, c)
   of nkEmpty..pred(nkSym), succ(nkSym)..nkNilLit, nkComesFrom,
      nkTemplateDef, nkTypeSection, nkProcDef, nkMethodDef, nkConverterDef,
-     nkMacroDef, nkFuncDef:
+     nkMacroDef, nkFuncDef, nkMixinStmt:
     discard
   of nkClosure:
     if n[1].kind == nkNilLit:

compiler/liftlocals.nim

@@ -43,7 +43,7 @@ proc liftLocals(n: PNode; i: int; c: var Ctx) =
   of nkSym:
     if interestingVar(it.sym):
       n[i] = lookupOrAdd(c, it.sym, it.info)
-  of procDefs, nkTypeSection: discard
+  of procDefs, nkTypeSection, nkMixinStmt: discard
   else:
     for i in 0..<it.safeLen:
       liftLocals(it, i, c)

compiler/nilcheck.nim

@@ -1260,7 +1260,7 @@ proc check(n: PNode, ctx: NilCheckerContext, map: NilMap): Check =
   of nkNone..pred(nkSym), succ(nkSym)..nkNilLit, nkTypeSection, nkProcDef, nkConverterDef,
       nkMethodDef, nkIteratorDef, nkMacroDef, nkTemplateDef, nkLambda, nkDo,
       nkFuncDef, nkConstSection, nkConstDef, nkIncludeStmt, nkImportStmt,
-      nkExportStmt, nkPragma, nkCommentStmt, nkBreakState, nkTypeOfExpr:
+      nkExportStmt, nkPragma, nkCommentStmt, nkBreakState, nkTypeOfExpr, nkMixinStmt:
 
     discard "don't follow this : same as varpartitions"
     result = Check(nilability: Nil, map: map)

compiler/optimizer.nim

@@ -150,7 +150,7 @@ proc analyse(c: var Con; b: var BasicBlock; n: PNode) =
   of nkNone..pred(nkSym), succ(nkSym)..nkNilLit, nkTypeSection, nkProcDef, nkConverterDef,
       nkMethodDef, nkIteratorDef, nkMacroDef, nkTemplateDef, nkLambda, nkDo,
       nkFuncDef, nkConstSection, nkConstDef, nkIncludeStmt, nkImportStmt,
-      nkExportStmt, nkPragma, nkCommentStmt, nkBreakState, nkTypeOfExpr:
+      nkExportStmt, nkPragma, nkCommentStmt, nkBreakState, nkTypeOfExpr, nkMixinStmt:
     discard "do not follow the construct"
 
   of nkAsgn, nkFastAsgn:

compiler/reorder.nim

@@ -105,6 +105,7 @@ proc computeDeps(cache: IdentCache; n: PNode, declares, uses: var IntSet; topLev
       decl(a[1])
     else:
       for i in 0..<n.safeLen: deps(n[i])
+  of nkMixinStmt: discard
   else:
     for i in 0..<n.safeLen: deps(n[i])
 

compiler/semdata.nim

@@ -42,6 +42,7 @@ type
     mappingExists*: bool
     mapping*: TIdTable
     caseContext*: seq[tuple[n: PNode, idx: int]]
+    localMixinStmts*: seq[PNode]
 
   TMatchedConcept* = object
     candidateType*: PType

compiler/semexprs.nim

@@ -75,7 +75,7 @@ proc semExprCheck(c: PContext, n: PNode, flags: TExprFlags): PNode =
     # bug #12741, redundant error messages are the lesser evil here:
     localError(c.config, n.info, errExprXHasNoType %
                 renderTree(result, {renderNoComments}))
-  
+
   if isEmpty:
     # do not produce another redundant error message:
     result = errorNode(c, n)
@@ -2944,6 +2944,12 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
     for i in 0..<n.len:
       n[i] = semExpr(c, n[i])
   of nkComesFrom: discard "ignore the comes from information for now"
+  of nkMixinStmt:
+    if c.p != nil:
+      c.p.localMixinStmts.add n
+    else:
+      localError(c.config, n.info, "invalid context for 'mixin' statement: " &
+                renderTree(n, {renderNoComments}))
   else:
     localError(c.config, n.info, "invalid expression: " &
                renderTree(n, {renderNoComments}))

compiler/seminst.nim

@@ -318,6 +318,15 @@ proc instantiateProcType(c: PContext, pt: TIdTable,
   prc.typ = result
   popInfoContext(c.config)
 
+proc fillMixinScope(c: PContext) =
+  var p = c.p
+  while p != nil:
+    for mix in p.localMixinStmts:
+      for choice in mix:
+        for n in choice:
+          addSym(c.currentScope, n.sym)
+    p = p.next
+
 proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
                       info: TLineInfo): PSym {.nosinks.} =
   ## Generates a new instance of a generic procedure.
@@ -344,6 +353,10 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
   result.ast = n
   pushOwner(c, result)
 
+  # mixin scope:
+  openScope(c)
+  fillMixinScope(c)
+
   openScope(c)
   let gp = n[genericParamsPos]
   internalAssert c.config, gp.kind != nkEmpty
@@ -394,6 +407,7 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
   popProcCon(c)
   popInfoContext(c.config)
   closeScope(c)           # close scope for parameters
+  closeScope(c)           # close scope for 'mixin' declarations
   popOwner(c)
   c.currentScope = oldScope
   discard c.friendModules.pop()

compiler/semparallel.nim

@@ -391,7 +391,8 @@ proc analyse(c: var AnalysisCtx; n: PNode) =
         addFactNeg(c.guards, canon(n[0], c.graph.operators))
     dec c.inLoop
   of nkTypeSection, nkProcDef, nkConverterDef, nkMethodDef, nkIteratorDef,
-      nkMacroDef, nkTemplateDef, nkConstSection, nkPragma, nkFuncDef:
+      nkMacroDef, nkTemplateDef, nkConstSection, nkPragma, nkFuncDef,
+      nkMixinStmt, nkExportStmt:
     discard
   else:
     analyseSons(c, n)

compiler/semstmts.nim

@@ -1823,8 +1823,8 @@ proc semMethodPrototype(c: PContext; s: PSym; n: PNode) =
       let t = tt[col]
       if t != nil and t.kind == tyGenericInvocation:
         var x = skipTypes(t[0], {tyVar, tyLent, tyPtr, tyRef, tyGenericInst,
-                                      tyGenericInvocation, tyGenericBody,
-                                      tyAlias, tySink, tyOwned})
+                                 tyGenericInvocation, tyGenericBody,
+                                 tyAlias, tySink, tyOwned})
         if x.kind == tyObject and t.len-1 == n[genericParamsPos].len:
           foundObj = true
           addMethodToGeneric(c.graph, c.module.position, x, col, s)

compiler/semtempl.nim

@@ -106,9 +106,10 @@ proc semBindStmt(c: PContext, n: PNode, toBind: var IntSet): PNode =
   result = newNodeI(nkEmpty, n.info)
 
 proc semMixinStmt(c: PContext, n: PNode, toMixin: var IntSet): PNode =
+  result = copyNode(n)
   for i in 0..<n.len:
     toMixin.incl(considerQuotedIdent(c, n[i]).id)
-  result = newNodeI(nkEmpty, n.info)
+    result.add symChoice(c, n[i], nil, scForceOpen)
 
 proc replaceIdentBySym(c: PContext; n: var PNode, s: PNode) =
   case n.kind

compiler/transf.nim

@@ -971,7 +971,7 @@ proc transform(c: PTransf, n: PNode): PNode =
   of nkConstSection:
     # do not replace ``const c = 3`` with ``const 3 = 3``
     return transformConstSection(c, n)
-  of nkTypeSection, nkTypeOfExpr:
+  of nkTypeSection, nkTypeOfExpr, nkMixinStmt:
     # no need to transform type sections:
     return n
   of nkVarSection, nkLetSection:

compiler/varpartitions.nim

@@ -631,7 +631,7 @@ const
     nkTypeSection, nkProcDef, nkConverterDef,
     nkMethodDef, nkIteratorDef, nkMacroDef, nkTemplateDef, nkLambda, nkDo,
     nkFuncDef, nkConstSection, nkConstDef, nkIncludeStmt, nkImportStmt,
-    nkExportStmt, nkPragma, nkCommentStmt, nkBreakState, nkTypeOfExpr}
+    nkExportStmt, nkPragma, nkCommentStmt, nkBreakState, nkTypeOfExpr, nkMixinStmt}
 
 proc potentialMutationViaArg(c: var Partitions; n: PNode; callee: PType) =
   if constParameters in c.goals and tfNoSideEffect in callee.flags:

compiler/vmgen.nim

@@ -2116,7 +2116,8 @@ proc gen(c: PCtx; n: PNode; dest: var TDest; flags: TGenFlags = {}) =
     else:
       dest = tmp0
   of nkEmpty, nkCommentStmt, nkTypeSection, nkConstSection, nkPragma,
-     nkTemplateDef, nkIncludeStmt, nkImportStmt, nkFromStmt, nkExportStmt:
+     nkTemplateDef, nkIncludeStmt, nkImportStmt, nkFromStmt, nkExportStmt,
+     nkMixinStmt:
     unused(c, n, dest)
   of nkStringToCString, nkCStringToString:
     gen(c, n[0], dest)

doc/manual.rst

@@ -5118,6 +5118,50 @@ scope is the default.
 ``bind`` statements only make sense in templates and generics.
 
 
+Delegating mixin statements
+---------------------------
+
+The following example outlines a problem that can arise when generic
+instantiations cross multiple different modules:
+
+.. code-block:: nim
+
+  # module A
+  proc genericA[T](x: T) =
+    mixin init
+    init(x)
+
+
+.. code-block:: nim
+
+  import C
+
+  # module B
+  proc genericB[T](x: T) =
+    # Without the `mixin init` statement C's init proc is
+    # not available when `genericB` is instantiated:
+    mixin init
+    genericA(x)
+
+.. code-block:: nim
+
+  # module C
+  type O = object
+  proc init(x: var O) = discard
+
+.. code-block:: nim
+
+  # module main
+  import B, C
+
+  genericB O()
+
+In module B has an `init` proc from module C in its scope that is not
+taken into account when `genericB` is instantiated which leads to the
+instantiation of `genericA`. The solution is to `forward`:idx these
+symbols by a `mixin` statement inside `genericB`.
+
+
 Templates
 =========
 

tests/sandwich/generic_library.nim

@@ -0,0 +1,6 @@
+
+proc libraryFunc*[T](x: T) =
+  mixin mixedIn, indirectlyMixedIn
+  echo mixedIn()
+  echo indirectlyMixedIn()
+

tests/sandwich/helper_module.nim

@@ -0,0 +1,3 @@
+
+proc indirectlyMixedIn*: int =
+  200

tests/sandwich/module_using_generic_library.nim

@@ -0,0 +1,12 @@
+
+import
+  generic_library, helper_module
+
+proc mixedIn: int = 100
+
+proc makeUseOfLibrary*[T](x: T) =
+  mixin mixedIn, indirectlyMixedIn
+  libraryFunc(x)
+
+when isMainModule:
+  makeUseOfLibrary "test"

tests/sandwich/tmain.nim

@@ -0,0 +1,9 @@
+discard """
+  output: '''100
+200'''
+"""
+
+import
+  module_using_generic_library
+
+makeUseOfLibrary "test"