fixes #3313

compiler/ast.nim

@@ -738,6 +738,8 @@ type
     name*: Rope
     path*: PNode              # can be a string literal!
 
+  CompilesId* = int ## id that is used for the caching logic within
+                    ## ``system.compiles``. See the seminst module.
   TInstantiation* = object
     sym*: PSym
     concreteTypes*: seq[PType]
@@ -745,6 +747,7 @@ type
                               # needed in caas mode for purging the cache
                               # XXX: it's possible to switch to a
                               # simple ref count here
+    compilesId*: CompilesId
 
   PInstantiation* = ref TInstantiation
 

compiler/semdata.nim

@@ -72,6 +72,7 @@ type
     inGenericContext*: int     # > 0 if we are in a generic type
     inUnrolledContext*: int    # > 0 if we are unrolling a loop
     inCompilesContext*: int    # > 0 if we are in a ``compiles`` magic
+    compilesContextIdGenerator*: int
     inGenericInst*: int        # > 0 if we are instantiating a generic
     converters*: TSymSeq       # sequence of converters
     patterns*: TSymSeq         # sequence of pattern matchers

compiler/semexprs.nim

@@ -1636,7 +1636,9 @@ proc tryExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
   # watch out, hacks ahead:
   let oldErrorCount = msgs.gErrorCounter
   let oldErrorMax = msgs.gErrorMax
-  inc c.inCompilesContext
+  let oldCompilesId = c.inCompilesContext
+  inc c.compilesContextIdGenerator
+  c.inCompilesContext = c.compilesContextIdGenerator
   # do not halt after first error:
   msgs.gErrorMax = high(int)
 
@@ -1660,6 +1662,7 @@ proc tryExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
   except ERecoverableError:
     discard
   # undo symbol table changes (as far as it's possible):
+  c.inCompilesContext = oldCompilesId
   c.generics = oldGenerics
   c.inGenericContext = oldInGenericContext
   c.inUnrolledContext = oldInUnrolledContext
@@ -1668,7 +1671,6 @@ proc tryExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
   msgs.setInfoContextLen(oldContextLen)
   setLen(gOwners, oldOwnerLen)
   c.currentScope = oldScope
-  dec c.inCompilesContext
   errorOutputs = oldErrorOutputs
   msgs.gErrorCounter = oldErrorCount
   msgs.gErrorMax = oldErrorMax

compiler/seminst.nim

@@ -47,10 +47,11 @@ proc sameInstantiation(a, b: TInstantiation): bool =
                           flags = {ExactTypeDescValues}): return
     result = true
 
-proc genericCacheGet(genericSym: PSym, entry: TInstantiation): PSym =
+proc genericCacheGet(genericSym: PSym, entry: TInstantiation;
+                     id: CompilesId): PSym =
   if genericSym.procInstCache != nil:
     for inst in genericSym.procInstCache:
-      if sameInstantiation(entry, inst[]):
+      if inst.compilesId == id and sameInstantiation(entry, inst[]):
         return inst.sym
 
 proc removeDefaultParamValues(n: PNode) =
@@ -249,13 +250,15 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
   if tfTriggersCompileTime in result.typ.flags:
     incl(result.flags, sfCompileTime)
   n.sons[genericParamsPos] = ast.emptyNode
-  var oldPrc = genericCacheGet(fn, entry[])
+  var oldPrc = genericCacheGet(fn, entry[], c.inCompilesContext)
   if oldPrc == nil:
     # we MUST not add potentially wrong instantiations to the caching mechanism.
     # This means recursive instantiations behave differently when in
     # a ``compiles`` context but this is the lesser evil. See
     # bug #1055 (tevilcompiles).
-    if c.inCompilesContext == 0: fn.procInstCache.safeAdd(entry)
+    #if c.inCompilesContext == 0:
+    entry.compilesId = c.inCompilesContext
+    fn.procInstCache.safeAdd(entry)
     c.generics.add(makeInstPair(fn, entry))
     if n.sons[pragmasPos].kind != nkEmpty:
       pragma(c, result, n.sons[pragmasPos], allRoutinePragmas)