fixes #4551

compiler/ccgexprs.nim

@@ -1980,6 +1980,9 @@ proc exprComplexConst(p: BProc, n: PNode, d: var TLoc) =
     fillLoc(d, locData, t, tmp, OnStatic)
   else:
     putDataIntoDest(p, d, t, tmp)
+    # This fixes bug #4551, but we really need better dataflow
+    # analysis to make this 100% safe.
+    d.s = OnStatic
 
 proc expr(p: BProc, n: PNode, d: var TLoc) =
   case n.kind

tests/ccgbugs/tcapture_static.nim

@@ -0,0 +1,13 @@
+discard """
+  output: '''hi'''
+"""
+
+# bug #4551
+
+proc foo() =
+    let arr = ["hi"]
+    for i, v in arr:
+        let bar = proc =
+            echo v
+        bar()
+foo()