implements https://github.com/nim-lang/RFCs/issues/257 (#15466)

compiler/parampatterns.nim

@@ -223,6 +223,8 @@ proc isAssignable*(owner: PSym, n: PNode; isUnsafeAddr=false): TAssignableResult
       result = arLValue
     elif isUnsafeAddr and n.sym.kind == skParam:
       result = arLValue
+    elif isUnsafeAddr and n.sym.kind == skConst and dontInlineConstant(n, n.sym.ast):
+      result = arLValue
     elif n.sym.kind in kinds:
       if owner != nil and owner == n.sym.owner and
           sfGlobal notin n.sym.flags:

compiler/transf.nim

@@ -850,13 +850,6 @@ proc transformExceptBranch(c: PTransf, n: PNode): PNode =
   else:
     result = transformSons(c, n)
 
-proc dontInlineConstant(orig, cnst: PNode): bool {.inline.} =
-  # symbols that expand to a complex constant (array, etc.) should not be
-  # inlined, unless it's the empty array:
-  result = orig.kind == nkSym and
-           cnst.kind in {nkCurly, nkPar, nkTupleConstr, nkBracket} and
-           cnst.len != 0
-
 proc commonOptimizations*(g: ModuleGraph; c: PSym, n: PNode): PNode =
   result = n
   for i in 0..<n.safeLen:

compiler/trees.nim

@@ -195,3 +195,10 @@ proc stupidStmtListExpr*(n: PNode): bool =
   for i in 0..<n.len-1:
     if n[i].kind notin {nkEmpty, nkCommentStmt}: return false
   result = true
+
+proc dontInlineConstant*(orig, cnst: PNode): bool {.inline.} =
+  # symbols that expand to a complex constant (array, etc.) should not be
+  # inlined, unless it's the empty array:
+  result = orig.kind == nkSym and
+           cnst.kind in {nkCurly, nkPar, nkTupleConstr, nkBracket} and
+           cnst.len != 0