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

tests/misc/mimportc.nim

@@ -0,0 +1,26 @@
+#[
+this test will grow with more importc+importcpp tests; see driver in trunner.nim
+]#
+
+{.emit:"""
+struct A {
+  static int fun0(int a){
+    return a;
+  }
+  static int& fun1(int& a){
+    return a;
+  }
+};
+""".}
+
+proc fun0*(a: cint): int {.importcpp:"A::$1(@)".}
+proc fun1*(a: var cint): var int {.importcpp:"A::$1(@)".} =
+  ## some comment; this test is for #14314
+  runnableExamples: discard
+
+proc main()=
+  var a = 10.cint
+  doAssert fun0(a) == a
+  doAssert fun1(a).addr == a.addr
+  echo "witness"
+main()

tests/trunner.nim

@@ -16,6 +16,10 @@ const mode =
   else: static: doAssert false
 
 const testsDir = currentSourcePath().parentDir
+const buildDir = testsDir.parentDir / "build"
+const nimcache = buildDir / "nimcacheTrunner"
+  # `querySetting(nimcacheDir)` would also be possible, but we thus
+  # avoid stomping on other parallel tests
 
 proc runCmd(file, options = ""): auto =
   let fileabs = testsDir / file.unixToNativePath
@@ -108,10 +112,6 @@ else: # don't run twice the same test
   block: # nim doc --backend:$backend --doccmd:$cmd
     # test for https://github.com/nim-lang/Nim/issues/13129
     # test for https://github.com/nim-lang/Nim/issues/13891
-    const buildDir = testsDir.parentDir / "build"
-    const nimcache = buildDir / "nimcacheTrunner"
-      # `querySetting(nimcacheDir)` would also be possible, but we thus
-      # avoid stomping on other parallel tests
     let file = testsDir / "nimdoc/m13129.nim"
     for backend in fmt"{mode} js".split:
       let cmd = fmt"{nim} doc -b:{backend} --nimcache:{nimcache} -d:m13129Foo1 --doccmd:'-d:m13129Foo2 --hints:off' --usenimcache --hints:off {file}"
@@ -122,3 +122,9 @@ else: # don't run twice the same test
     block: # mak sure --backend works with `nim r`
       let cmd = fmt"{nim} r --backend:{mode} --hints:off --nimcache:{nimcache} {file}"
       check execCmdEx(cmd) == ("ok3\n", 0)
+
+  block: # some importc tests
+    # issue #14314
+    let file = testsDir / "misc/mimportc.nim"
+    let cmd = fmt"{nim} r -b:cpp --hints:off --nimcache:{nimcache} --warningAsError:ProveInit {file}"
+    check execCmdEx(cmd) == ("witness\n", 0)