Allow assignment of nested non-closure procs to globals (#25154)

For memory-safety, this only seems problematic in case of closures, so I
just special cased that.

Fixes #25131

Author: bptato

compiler/semstmts.nim

@@ -725,7 +725,7 @@ template isLocalSym(sym: PSym): bool =
       sym.typ.kind == tyTypeDesc or
       sfCompileTime in sym.flags) or
       sym.kind in {skProc, skFunc, skIterator} and
-      sfGlobal notin sym.flags
+      sfGlobal notin sym.flags and sym.typ.callConv == ccClosure
 
 proc usesLocalVar(n: PNode): bool =
   case n.kind

tests/global/tglobalclosure.nim

@@ -0,0 +1,14 @@
+discard """
+  errormsg: "cannot assign local to global variable"
+  line: 11
+"""
+
+proc main() =
+  var x = "hi"
+  proc p() =
+    echo x
+
+  let a {.global.} = p
+  p()
+
+main()

tests/global/tglobalclosure2.nim

@@ -0,0 +1,17 @@
+discard """
+  errormsg: "cannot assign local to global variable"
+  line: 14
+"""
+
+type X = object
+  p: proc() {.closure.}
+
+proc main() =
+  var x = "hi"
+  proc p() =
+    echo x
+
+  let a {.global.} = X(p: p)
+  a.p()
+
+main()

tests/global/tglobalproc.nim

@@ -0,0 +1,17 @@
+discard """
+output: "hi\nhi"
+"""
+
+type X = object
+  p: proc() {.nimcall.}
+
+proc main() =
+  proc p() =
+    echo "hi"
+
+  let a {.global.} = p
+  let b {.global.} = X(p: p)
+  a()
+  b.p()
+
+main()