From d85b7dde7b0aabe64b51baf7e3c23506fa533f8a Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Tue, 9 Mar 2021 20:19:24 +0100
Subject: [PATCH] fixes #11225; generic sandwich problems; [backport:1.2]
 (#17255)

* fixes #11225; generic sandwich problems; [backport:1.2]
* progress
* delegating these symbols must be done via 'bind'

(cherry picked from commit 2f213db7eed7fb715b803559b38af4148cff02e1)
---
 compiler/ccgexprs.nim                         |  1 +
 compiler/cgen.nim                             |  3 +-
 compiler/closureiters.nim                     |  2 +-
 compiler/injectdestructors.nim                |  3 +-
 compiler/jsgen.nim                            |  3 +-
 compiler/lambdalifting.nim                    |  5 ++-
 compiler/liftlocals.nim                       |  2 +-
 compiler/reorder.nim                          |  1 +
 compiler/semdata.nim                          |  1 +
 compiler/semexprs.nim                         |  7 +++
 compiler/seminst.nim                          | 13 ++++++
 compiler/semparallel.nim                      |  3 +-
 compiler/semstmts.nim                         |  4 +-
 compiler/semtempl.nim                         | 10 +++--
 compiler/transf.nim                           |  2 +-
 compiler/vmgen.nim                            |  3 +-
 doc/manual.rst                                | 44 +++++++++++++++++++
 tests/sandwich/generic_library.nim            |  6 +++
 tests/sandwich/helper_module.nim              |  3 ++
 .../sandwich/module_using_generic_library.nim | 12 +++++
 tests/sandwich/tmain.nim                      |  9 ++++
 21 files changed, 122 insertions(+), 15 deletions(-)
 create mode 100644 tests/sandwich/generic_library.nim
 create mode 100644 tests/sandwich/helper_module.nim
 create mode 100644 tests/sandwich/module_using_generic_library.nim
 create mode 100644 tests/sandwich/tmain.nim

diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index 53f60cb09b..7380aa9855 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -2744,6 +2744,7 @@ proc expr(p: BProc, n: PNode, d: var TLoc) =
     inc p.splitDecls
     genGotoState(p, n)
   of nkBreakState: genBreakState(p, n, d)
+  of nkMixinStmt, nkBindStmt: discard
   else: internalError(p.config, n.info, "expr(" & $n.kind & "); unknown node kind")
 
 proc genNamedConstExpr(p: BProc, n: PNode; isConst: bool): Rope =
diff --git a/compiler/cgen.nim b/compiler/cgen.nim
index e046d1298e..4d9b662ed9 100644
--- a/compiler/cgen.nim
+++ b/compiler/cgen.nim
@@ -838,7 +838,8 @@ 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, nkBindStmt} +
                   declarativeDefs
 
 proc easyResultAsgn(n: PNode): PNode =
diff --git a/compiler/closureiters.nim b/compiler/closureiters.nim
index 98249c065c..2b87743a86 100644
--- a/compiler/closureiters.nim
+++ b/compiler/closureiters.nim
@@ -156,7 +156,7 @@ type
 
 const
   nkSkip = {nkEmpty..nkNilLit, nkTemplateDef, nkTypeSection, nkStaticStmt,
-            nkCommentStmt} + procDefs
+            nkCommentStmt, nkMixinStmt, nkBindStmt} + procDefs
 
 proc newStateAccess(ctx: var Ctx): PNode =
   if ctx.stateVarSym.isNil:
diff --git a/compiler/injectdestructors.nim b/compiler/injectdestructors.nim
index 6b727caac8..f1bff6b9b0 100644
--- a/compiler/injectdestructors.nim
+++ b/compiler/injectdestructors.nim
@@ -945,7 +945,8 @@ proc p(n: PNode; c: var Con; mode: ProcessMode): PNode =
     of nkNone..nkNilLit, nkTypeSection, nkProcDef, nkConverterDef,
        nkMethodDef, nkIteratorDef, nkMacroDef, nkTemplateDef, nkLambda, nkDo,
        nkFuncDef, nkConstSection, nkConstDef, nkIncludeStmt, nkImportStmt,
-       nkExportStmt, nkPragma, nkCommentStmt, nkBreakState:
+       nkExportStmt, nkPragma, nkCommentStmt, nkBreakState,
+       nkMixinStmt, nkBindStmt:
       result = n
     of nkBreakStmt:
       inc c.hasUnstructuredCf
diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index ba10e0497e..bdeacbc205 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -2479,7 +2479,8 @@ proc gen(p: PProc, n: PNode, r: var TCompRes) =
   of nkRaiseStmt: genRaiseStmt(p, n)
   of nkTypeSection, nkCommentStmt, nkIteratorDef, nkIncludeStmt,
      nkImportStmt, nkImportExceptStmt, nkExportStmt, nkExportExceptStmt,
-     nkFromStmt, nkTemplateDef, nkMacroDef, nkStaticStmt: discard
+     nkFromStmt, nkTemplateDef, nkMacroDef, nkStaticStmt,
+     nkMixinStmt, nkBindStmt: discard
   of nkPragma: genPragma(p, n)
   of nkProcDef, nkFuncDef, nkMethodDef, nkConverterDef:
     var s = n[namePos].sym
diff --git a/compiler/lambdalifting.nim b/compiler/lambdalifting.nim
index 01def12ada..15f1bcab7d 100644
--- a/compiler/lambdalifting.nim
+++ b/compiler/lambdalifting.nim
@@ -493,7 +493,8 @@ 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, nkBindStmt:
     discard
   of nkLambdaKinds, nkIteratorDef:
     if n.typ != nil:
@@ -747,7 +748,7 @@ proc liftCapturedVars(n: PNode; owner: PSym; d: 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, nkBindStmt:
     discard
   of nkClosure:
     if n[1].kind == nkNilLit:
diff --git a/compiler/liftlocals.nim b/compiler/liftlocals.nim
index 672dca5d9e..08daa8dfb6 100644
--- a/compiler/liftlocals.nim
+++ b/compiler/liftlocals.nim
@@ -42,7 +42,7 @@ 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, nkBindStmt: discard
   else:
     for i in 0..<it.safeLen:
       liftLocals(it, i, c)
diff --git a/compiler/reorder.nim b/compiler/reorder.nim
index 6318065876..d82d294556 100644
--- a/compiler/reorder.nim
+++ b/compiler/reorder.nim
@@ -106,6 +106,7 @@ 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, nkBindStmt: discard
   else:
     for i in 0..<n.safeLen: deps(n[i])
 
diff --git a/compiler/semdata.nim b/compiler/semdata.nim
index 458b4a807f..2d267121e9 100644
--- a/compiler/semdata.nim
+++ b/compiler/semdata.nim
@@ -38,6 +38,7 @@ type
     mappingExists*: bool
     mapping*: TIdTable
     caseContext*: seq[tuple[n: PNode, idx: int]]
+    localBindStmts*: seq[PNode]
 
   TMatchedConcept* = object
     candidateType*: PType
diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 07a8f69523..cdd45a672a 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -2830,6 +2830,13 @@ 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: discard
+  of nkBindStmt:
+    if c.p != nil:
+      c.p.localBindStmts.add n
+    else:
+      localError(c.config, n.info, "invalid context for 'bind' statement: " &
+                renderTree(n, {renderNoComments}))
   else:
     localError(c.config, n.info, "invalid expression: " &
                renderTree(n, {renderNoComments}))
diff --git a/compiler/seminst.nim b/compiler/seminst.nim
index 605ddfafaf..451b0ab621 100644
--- a/compiler/seminst.nim
+++ b/compiler/seminst.nim
@@ -319,6 +319,14 @@ proc instantiateProcType(c: PContext, pt: TIdTable,
   prc.typ = result
   popInfoContext(c.config)
 
+proc fillMixinScope(c: PContext) =
+  var p = c.p
+  while p != nil:
+    for bnd in p.localBindStmts:
+      for n in bnd:
+        addSym(c.currentScope, n.sym)
+    p = p.next
+
 proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
                       info: TLineInfo): PSym =
   ## Generates a new instance of a generic procedure.
@@ -345,6 +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
@@ -395,6 +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()
diff --git a/compiler/semparallel.nim b/compiler/semparallel.nim
index 5614f9ee37..4083286dd3 100644
--- a/compiler/semparallel.nim
+++ b/compiler/semparallel.nim
@@ -391,7 +391,8 @@ proc analyse(c: var AnalysisCtx; n: PNode) =
         addFactNeg(c.guards, canon(n[0], c.guards.o))
     dec c.inLoop
   of nkTypeSection, nkProcDef, nkConverterDef, nkMethodDef, nkIteratorDef,
-      nkMacroDef, nkTemplateDef, nkConstSection, nkPragma, nkFuncDef:
+      nkMacroDef, nkTemplateDef, nkConstSection, nkPragma, nkFuncDef,
+      nkMixinStmt, nkBindStmt, nkExportStmt:
     discard
   else:
     analyseSons(c, n)
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index 1e75dbdbc0..92ae94272b 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -1828,8 +1828,8 @@ 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
           x.methods.add((col,s))
diff --git a/compiler/semtempl.nim b/compiler/semtempl.nim
index dedea2e995..9238973dff 100644
--- a/compiler/semtempl.nim
+++ b/compiler/semtempl.nim
@@ -86,6 +86,7 @@ proc symChoice(c: PContext, n: PNode, s: PSym, r: TSymChoiceRule;
       a = nextOverloadIter(o, c, n)
 
 proc semBindStmt(c: PContext, n: PNode, toBind: var IntSet): PNode =
+  result = copyNode(n)
   for i in 0..<n.len:
     var a = n[i]
     # If 'a' is an overloaded symbol, we used to use the first symbol
@@ -99,16 +100,19 @@ proc semBindStmt(c: PContext, n: PNode, toBind: var IntSet): PNode =
       let sc = symChoice(c, n, s, scClosed)
       if sc.kind == nkSym:
         toBind.incl(sc.sym.id)
+        result.add sc
       else:
-        for x in items(sc): toBind.incl(x.sym.id)
+        for x in items(sc):
+          toBind.incl(x.sym.id)
+          result.add x
     else:
       illFormedAst(a, c.config)
-  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
diff --git a/compiler/transf.nim b/compiler/transf.nim
index e9012f7eab..b61ce9f919 100644
--- a/compiler/transf.nim
+++ b/compiler/transf.nim
@@ -993,7 +993,7 @@ 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, nkBindStmt:
     # no need to transform type sections:
     return n
   of nkVarSection, nkLetSection:
diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim
index 25e59b448b..fb81335b2f 100644
--- a/compiler/vmgen.nim
+++ b/compiler/vmgen.nim
@@ -2106,7 +2106,8 @@ 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, nkBindStmt:
     unused(c, n, dest)
   of nkStringToCString, nkCStringToString:
     gen(c, n[0], dest)
diff --git a/doc/manual.rst b/doc/manual.rst
index f7a255e4fe..44bb3b6a85 100644
--- a/doc/manual.rst
+++ b/doc/manual.rst
@@ -4789,6 +4789,50 @@ scope is the default.
 ``bind`` statements only make sense in templates and generics.
 
 
+Delegating bind 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 `bind init` statement C's init proc is
+    # not available when `genericB` is instantiated:
+    bind 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 `bind` statement inside `genericB`.
+
+
 Templates
 =========
 
diff --git a/tests/sandwich/generic_library.nim b/tests/sandwich/generic_library.nim
new file mode 100644
index 0000000000..43e7bd65f2
--- /dev/null
+++ b/tests/sandwich/generic_library.nim
@@ -0,0 +1,6 @@
+
+proc libraryFunc*[T](x: T) =
+  mixin mixedIn, indirectlyMixedIn
+  echo mixedIn()
+  echo indirectlyMixedIn()
+
diff --git a/tests/sandwich/helper_module.nim b/tests/sandwich/helper_module.nim
new file mode 100644
index 0000000000..d003bf0441
--- /dev/null
+++ b/tests/sandwich/helper_module.nim
@@ -0,0 +1,3 @@
+
+proc indirectlyMixedIn*: int =
+  200
diff --git a/tests/sandwich/module_using_generic_library.nim b/tests/sandwich/module_using_generic_library.nim
new file mode 100644
index 0000000000..bbb0d92a4a
--- /dev/null
+++ b/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) =
+  bind mixedIn, indirectlyMixedIn
+  libraryFunc(x)
+
+when isMainModule:
+  makeUseOfLibrary "test"
diff --git a/tests/sandwich/tmain.nim b/tests/sandwich/tmain.nim
new file mode 100644
index 0000000000..aa50bfb049
--- /dev/null
+++ b/tests/sandwich/tmain.nim
@@ -0,0 +1,9 @@
+discard """
+  output: '''100
+200'''
+"""
+
+import
+  module_using_generic_library
+
+makeUseOfLibrary "test"