Fix #5127

compiler/semstmts.nim

@@ -1740,7 +1740,7 @@ proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
 
           let verdict = semConstExpr(c, n[i])
           if verdict.intVal == 0:
-            localError(result.info, "type class predicate failed")
+            localError(result.info, "concept predicate failed")
         of tyUnknown: continue
         else: discard
       if n.sons[i].typ == enforceVoidContext: #or usesResult(n.sons[i]):

compiler/sigmatch.nim

@@ -1040,11 +1040,12 @@ proc typeRelImpl(c: var TCandidate, f, aOrig: PType,
            else: isNone
 
   of tyUserTypeClass, tyUserTypeClassInst:
-    # consider this: 'var g: Node' *within* a concept where 'Node'
-    # is a concept too (tgraph)
-    let x = typeRel(c, a, f, flags + {trDontBind})
-    if x >= isGeneric:
-      return isGeneric
+    if c.c.matchedConcept != nil:
+      # consider this: 'var g: Node' *within* a concept where 'Node'
+      # is a concept too (tgraph)
+      let x = typeRel(c, a, f, flags + {trDontBind})
+      if x >= isGeneric:
+        return isGeneric
   else: discard
 
   case f.kind

tests/concepts/texplain.nim

@@ -9,33 +9,33 @@ proc e(o: ExplainedConcept): int
 texplain.nim(65, 6) ExplainedConcept: undeclared field: 'foo'
 texplain.nim(65, 6) ExplainedConcept: undeclared field: '.'
 texplain.nim(65, 6) ExplainedConcept: expression '.' cannot be called
-texplain.nim(65, 5) ExplainedConcept: type class predicate failed
+texplain.nim(65, 5) ExplainedConcept: concept predicate failed
 texplain.nim(66, 6) ExplainedConcept: undeclared field: 'bar'
 texplain.nim(66, 6) ExplainedConcept: undeclared field: '.'
 texplain.nim(66, 6) ExplainedConcept: expression '.' cannot be called
-texplain.nim(65, 5) ExplainedConcept: type class predicate failed
+texplain.nim(65, 5) ExplainedConcept: concept predicate failed
 
 texplain.nim(105, 10) Hint: Non-matching candidates for e(10)
 proc e(o: ExplainedConcept): int
 texplain.nim(65, 6) ExplainedConcept: undeclared field: 'foo'
 texplain.nim(65, 6) ExplainedConcept: undeclared field: '.'
 texplain.nim(65, 6) ExplainedConcept: expression '.' cannot be called
-texplain.nim(65, 5) ExplainedConcept: type class predicate failed
+texplain.nim(65, 5) ExplainedConcept: concept predicate failed
 texplain.nim(66, 6) ExplainedConcept: undeclared field: 'bar'
 texplain.nim(66, 6) ExplainedConcept: undeclared field: '.'
 texplain.nim(66, 6) ExplainedConcept: expression '.' cannot be called
-texplain.nim(65, 5) ExplainedConcept: type class predicate failed
+texplain.nim(65, 5) ExplainedConcept: concept predicate failed
 
 texplain.nim(109, 20) Error: type mismatch: got (NonMatchingType)
 but expected one of: 
 proc e(o: ExplainedConcept): int
-texplain.nim(65, 5) ExplainedConcept: type class predicate failed
+texplain.nim(65, 5) ExplainedConcept: concept predicate failed
 proc e(i: int): int
 
 texplain.nim(110, 20) Error: type mismatch: got (NonMatchingType)
 but expected one of: 
 proc r(o: RegularConcept): int
-texplain.nim(69, 5) RegularConcept: type class predicate failed
+texplain.nim(69, 5) RegularConcept: concept predicate failed
 proc r[T](a: SomeNumber; b: T; c: auto)
 proc r(i: string): int
 
@@ -49,12 +49,12 @@ proc f(o: NestedConcept)
 texplain.nim(69, 6) RegularConcept: undeclared field: 'foo'
 texplain.nim(69, 6) RegularConcept: undeclared field: '.'
 texplain.nim(69, 6) RegularConcept: expression '.' cannot be called
-texplain.nim(69, 5) RegularConcept: type class predicate failed
+texplain.nim(69, 5) RegularConcept: concept predicate failed
 texplain.nim(70, 6) RegularConcept: undeclared field: 'bar'
 texplain.nim(70, 6) RegularConcept: undeclared field: '.'
 texplain.nim(70, 6) RegularConcept: expression '.' cannot be called
-texplain.nim(69, 5) RegularConcept: type class predicate failed
-texplain.nim(73, 5) NestedConcept: type class predicate failed
+texplain.nim(69, 5) RegularConcept: concept predicate failed
+texplain.nim(73, 5) NestedConcept: concept predicate failed
 '''
   line: 119
   errormsg: "type mismatch: got (MatchingType)"

tests/concepts/tgraph.nim

@@ -1,29 +1,34 @@
-discard """
-  output: '''XY is Node
-MyGraph is Graph'''
-"""
 # bug #3452
 import math
 
 type
-    Node* = concept n
-        `==`(n, n) is bool
+  Node* = concept n
+    `==`(n, n) is bool
 
-    Graph* = concept g
-        var x: Node
-        distance(g, x, x) is float
+  Graph1* = concept g
+    type N = Node
+    distance(g, N, N) is float
 
-    XY* = tuple[x, y: int]
+  Graph2 = concept g
+    distance(g, Node, Node) is float
 
-    MyGraph* = object
-        points: seq[XY]
+  Graph3 = concept g
+    var x: Node
+    distance(g, x, x) is float
 
-if XY is Node:
-    echo "XY is Node"
+  XY* = tuple[x, y: int]
+
+  MyGraph* = object
+    points: seq[XY]
+
+static:
+  assert XY is Node
 
 proc distance*( g: MyGraph, a, b: XY): float =
-    sqrt( pow(float(a.x - b.x), 2) + pow(float(a.y - b.y), 2) )
+  sqrt( pow(float(a.x - b.x), 2) + pow(float(a.y - b.y), 2) )
 
-if MyGraph is Graph:
-    echo "MyGraph is Graph"
+static:
+  assert MyGraph is Graph1
+  assert MyGraph is Graph2
+  assert MyGraph is Graph3
 

tests/concepts/twrapconcept.nim

@@ -0,0 +1,22 @@
+discard """
+  errormsg: "type mismatch: got (string)"
+  line: 21
+  nimout: "twrapconcept.nim(11, 5) Foo: concept predicate failed"
+"""
+
+# https://github.com/nim-lang/Nim/issues/5127
+
+type
+  Foo = concept foo
+    foo.get is int
+
+  FooWrap[F: Foo] = object
+    foo: F
+
+proc get(x: int): int = x
+
+proc wrap[F: Foo](foo: F): FooWrap[F] = FooWrap[F](foo: foo)
+
+let x = wrap(12)
+let y = wrap "string"
+