fixes #1547

compiler/ccgexprs.nim

@@ -1718,7 +1718,7 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
 
 proc genConstExpr(p: BProc, n: PNode): PRope
 proc handleConstExpr(p: BProc, n: PNode, d: var TLoc): bool =
-  if (nfAllConst in n.flags) and (d.k == locNone) and (sonsLen(n) > 0):
+  if nfAllConst in n.flags and d.k == locNone and n.len > 0 and n.isDeepConstExpr:
     var t = getUniqueType(n.typ)
     discard getTypeDesc(p.module, t) # so that any fields are initialized
     var id = nodeTableTestOrSet(p.module.dataCache, n, gBackendId)

compiler/trees.nim

@@ -117,7 +117,9 @@ proc isDeepConstExpr*(n: PNode): bool =
   of nkCurly, nkBracket, nkPar, nkObjConstr, nkClosure:
     for i in 0 .. <n.len:
       if not isDeepConstExpr(n.sons[i]): return false
-    result = true
+    # XXX once constant objects are supported by the codegen this needs to be
+    # weakened:
+    result = n.typ.isNil or n.typ.skipTypes({tyGenericInst, tyDistinct}).kind != tyObject
   else: discard
 
 proc flattenTreeAux(d, a: PNode, op: TMagic) = 

tests/ccgbugs/tconstobj.nim

@@ -0,0 +1,16 @@
+discard """
+  output: '''(FirstName: James, LastName: Franco)'''
+"""
+
+# bug #1547
+import tables
+
+type Person* = object
+    FirstName*: string
+    LastName*: string
+
+let people = {
+    "001": Person(FirstName: "James", LastName: "Franco")
+}.toTable()
+
+echo people["001"]