fix #14314 do not analyze importc procs for effects (#14319)

compiler/lineinfos.nim

@@ -23,7 +23,7 @@ type
     errGeneralParseError,
     errNewSectionExpected,
     errInvalidDirectiveX,
-    errProveInit,
+    errProveInit, # deadcode
     errGenerated,
     errUser,
     warnCannotOpenFile,
@@ -66,7 +66,7 @@ const
     errGeneralParseError: "general parse error",
     errNewSectionExpected: "new section expected",
     errInvalidDirectiveX: "invalid directive: '$1'",
-    errProveInit: "Cannot prove that '$1' is initialized.",
+    errProveInit: "Cannot prove that '$1' is initialized.",  # deadcode
     errGenerated: "$1",
     errUser: "$1",
     warnCannotOpenFile: "cannot open '$1'",

compiler/sempass2.nim

@@ -1151,12 +1151,17 @@ proc initEffects(g: ModuleGraph; effects: PNode; s: PSym; t: var TEffects; c: PC
   t.config = g.config
   t.c = c
 
+proc hasRealBody(s: PSym): bool =
+  ## also handles importc procs with runnableExamples, which requires `=`,
+  ## which is not a real implementation, refs #14314
+  result = {sfForward, sfImportc} * s.flags == {}
+
 proc trackProc*(c: PContext; s: PSym, body: PNode) =
   let g = c.graph
   var effects = s.typ.n[0]
   if effects.kind != nkEffectList: return
   # effects already computed?
-  if sfForward in s.flags: return
+  if not s.hasRealBody: return
   if effects.len == effectListLen: return
 
   var t: TEffects