From 5fd9bf9cd52a19b0ddd59452d9ebde0715d7d890 Mon Sep 17 00:00:00 2001
From: LemonBoy <LemonBoy@users.noreply.github.com>
Date: Sun, 10 Feb 2019 22:07:51 +0100
Subject: [PATCH] Propagate tfGcSafe flag to generic instantiations (#10620)

Fixes a nasty endless loop in the generic instantiation phase.
---
 compiler/semtypinst.nim              |  5 ++---
 tests/generics/tgenerics_various.nim | 11 +++++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/compiler/semtypinst.nim b/compiler/semtypinst.nim
index ebe822cdfca33..ceabd8e60dee7 100644
--- a/compiler/semtypinst.nim
+++ b/compiler/semtypinst.nim
@@ -300,7 +300,6 @@ proc instCopyType*(cl: var TReplTypeVars, t: PType): PType =
 proc handleGenericInvocation(cl: var TReplTypeVars, t: PType): PType =
   # tyGenericInvocation[A, tyGenericInvocation[A, B]]
   # is difficult to handle:
-  const eqFlags = eqTypeFlags + {tfGcSafe}
   var body = t.sons[0]
   if body.kind != tyGenericBody:
     internalError(cl.c.config, cl.info, "no generic body")
@@ -311,7 +310,7 @@ proc handleGenericInvocation(cl: var TReplTypeVars, t: PType): PType =
   else:
     result = searchInstTypes(t)
 
-  if result != nil and eqFlags*result.flags == eqFlags*t.flags:
+  if result != nil and sameFlags(result, t):
     when defined(reportCacheHits):
       echo "Generic instantiation cached ", typeToString(result), " for ", typeToString(t)
     return
@@ -329,7 +328,7 @@ proc handleGenericInvocation(cl: var TReplTypeVars, t: PType): PType =
   if header != t:
     # search again after first pass:
     result = searchInstTypes(header)
-    if result != nil and eqFlags*result.flags == eqFlags*t.flags:
+    if result != nil and sameFlags(result, t):
       when defined(reportCacheHits):
         echo "Generic instantiation cached ", typeToString(result), " for ",
           typeToString(t), " header ", typeToString(header)
diff --git a/tests/generics/tgenerics_various.nim b/tests/generics/tgenerics_various.nim
index 9e61865340f8f..656bfa566e8ac 100644
--- a/tests/generics/tgenerics_various.nim
+++ b/tests/generics/tgenerics_various.nim
@@ -242,3 +242,14 @@ block tvarargs_vs_generics:
   withDirectType "string"
   withOpenArray "string"
   withVarargs "string"
+
+block:
+  type
+    Que[T] {.gcsafe.} = object
+      x: T
+
+  proc `=`[T](q: var Que[T]; x: Que[T]) =
+    discard
+
+  var x: Que[int]
+  doAssert(x.x == 0)