fixes #3452

compiler/semcall.nim

@@ -95,7 +95,7 @@ proc notFoundError*(c: PContext, n: PNode, errors: CandidateErrors) =
   # Gives a detailed error message; this is separated from semOverloadedCall,
   # as semOverlodedCall is already pretty slow (and we need this information
   # only in case of an error).
-  if c.compilesContextId > 0:
+  if c.compilesContextId > 0 and optReportConceptFailures notin gGlobalOptions:
     # fail fast:
     globalError(n.info, errTypeMismatch, "")
   if errors.isNil or errors.len == 0:
@@ -133,6 +133,9 @@ proc notFoundError*(c: PContext, n: PNode, errors: CandidateErrors) =
     add(candidates, "\n")
   if candidates != "":
     add(result, "\n" & msgKindToString(errButExpected) & "\n" & candidates)
+  if c.compilesContextId > 0 and optReportConceptFailures in gGlobalOptions:
+    globalError(n.info, errGenerated, result)
+  else:
     localError(n.info, errGenerated, result)
 
 proc gatherUsedSyms(c: PContext, usedSyms: var seq[PNode]) =

compiler/sigmatch.nim

@@ -684,6 +684,13 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
   of tyAnything:
     return if f.kind == tyAnything: isGeneric
            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, false)
+    if x >= isGeneric:
+      return isGeneric
   else: discard
 
   case f.kind

tests/concepts/tgraph.nim

@@ -0,0 +1,29 @@
+discard """
+  output: '''XY is Node
+MyGraph is Graph'''
+"""
+# bug #3452
+import math
+
+type
+    Node* = concept n
+        `==`(n, n) is bool
+
+    Graph* = concept g
+        var x: Node
+        distance(g, x, x) is float
+
+    XY* = tuple[x, y: int]
+
+    MyGraph* = object
+        points: seq[XY]
+
+if XY is Node:
+    echo "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) )
+
+if MyGraph is Graph:
+    echo "MyGraph is Graph"
+