From 8f4b3743277119a0ec231738fdd3931476c186d9 Mon Sep 17 00:00:00 2001
From: Zahary Karadjov <zahary@gmail.com>
Date: Mon, 19 Jun 2017 20:07:26 +0300
Subject: [PATCH] Fix #4020; Better handling of templates within concepts

---
 compiler/ast.nim                       |  4 +-
 compiler/astalgo.nim                   |  2 +
 compiler/evaltempl.nim                 |  2 +
 compiler/semstmts.nim                  |  3 +-
 tests/concepts/templatesinconcepts.nim | 56 ++++++++++++++++++++++++++
 5 files changed, 65 insertions(+), 2 deletions(-)
 create mode 100644 tests/concepts/templatesinconcepts.nim

diff --git a/compiler/ast.nim b/compiler/ast.nim
index 63b656715..6e651ed00 100644
--- a/compiler/ast.nim
+++ b/compiler/ast.nim
@@ -453,6 +453,7 @@ type
     nfIsRef     # this node is a 'ref' node; used for the VM
     nfPreventCg # this node should be ignored by the codegen
     nfBlockArg  # this a stmtlist appearing in a call (e.g. a do block)
+    nfFromTemplate # a top-level node returned from a template
 
   TNodeFlags* = set[TNodeFlag]
   TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: beyond that)
@@ -956,7 +957,8 @@ const
     skMacro, skTemplate, skConverter, skEnumField, skLet, skStub, skAlias}
   PersistentNodeFlags*: TNodeFlags = {nfBase2, nfBase8, nfBase16,
                                       nfDotSetter, nfDotField,
-                                      nfIsRef, nfPreventCg, nfLL}
+                                      nfIsRef, nfPreventCg, nfLL,
+                                      nfFromTemplate}
   namePos* = 0
   patternPos* = 1    # empty except for term rewriting macros
   genericParamsPos* = 2
diff --git a/compiler/astalgo.nim b/compiler/astalgo.nim
index ebe080468..e32fff181 100644
--- a/compiler/astalgo.nim
+++ b/compiler/astalgo.nim
@@ -407,6 +407,8 @@ proc debugTree(n: PNode, indent: int, maxRecDepth: int;
     var istr = rspaces(indent + 2)
     result = "{$N$1\"kind\": $2" %
              [istr, makeYamlString($n.kind)]
+    when defined(useNodeIds):
+      addf(result, ",$N$1\"id\": $2", [istr, rope(n.id)])
     addf(result, ",$N$1\"info\": $2", [istr, lineInfoToStr(n.info)])
     if maxRecDepth != 0:
       addf(result, ",$N$1\"flags\": $2", [istr, rope($n.flags)])
diff --git a/compiler/evaltempl.nim b/compiler/evaltempl.nim
index fda0b79dd..f088afcdb 100644
--- a/compiler/evaltempl.nim
+++ b/compiler/evaltempl.nim
@@ -155,5 +155,7 @@ proc evalTemplate*(n: PNode, tmpl, genSymOwner: PSym; fromHlo=false): PNode =
     #if ctx.instLines: result.info = n.info
     for i in countup(0, safeLen(body) - 1):
       evalTemplateAux(body.sons[i], args, ctx, result)
+  result.flags.incl nfFromTemplate
   result = wrapInComesFrom(n.info, result)
   dec(evalTemplateCounter)
+
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index b00e9a9c0..8e019e4f6 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -1761,7 +1761,8 @@ proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
     else:
       var expr = semExpr(c, n.sons[i], flags)
       n.sons[i] = expr
-      if c.matchedConcept != nil and expr.typ != nil:
+      if c.matchedConcept != nil and expr.typ != nil and
+         (nfFromTemplate notin n.flags or i != last):
         case expr.typ.kind
         of tyBool:
           if expr.kind == nkInfix and
diff --git a/tests/concepts/templatesinconcepts.nim b/tests/concepts/templatesinconcepts.nim
new file mode 100644
index 000000000..292b97ea6
--- /dev/null
+++ b/tests/concepts/templatesinconcepts.nim
@@ -0,0 +1,56 @@
+import typetraits
+
+template typeLen(x): int = x.type.name.len
+
+template bunchOfChecks(x) =
+  x.typeLen > 3
+  x != 10 is bool
+
+template stmtListExprTmpl(x: untyped): untyped =
+  x is int
+  x
+
+type
+  Obj = object
+    x: int
+
+  Gen[T] = object
+    x: T
+
+  Eq = concept x, y
+    (x == y) is bool
+
+  NotEq = concept x, y
+    (x != y) is bool
+
+  ConceptUsingTemplate1 = concept x
+    echo x
+    sizeof(x) is int
+    bunchOfChecks x
+
+  ConceptUsingTemplate2 = concept x
+    stmtListExprTmpl x
+
+template ok(x) =
+  static: assert(x)
+
+template no(x) =
+  static: assert(not(x))
+
+ok int is Eq
+ok int is NotEq
+ok string is Eq
+ok string is NotEq
+ok Obj is Eq
+ok Obj is NotEq
+ok Gen[string] is Eq
+ok Gen[int] is NotEq
+
+no int is ConceptUsingTemplate1
+ok float is ConceptUsingTemplate1
+no string is ConceptUsingTemplate1
+
+ok int is ConceptUsingTemplate2
+no float is ConceptUsingTemplate2
+no string is ConceptUsingTemplate2
+