add custom pragma support for var and let symbols (#9582)

* add custom pragma support for var and let symbols
* updated changelog for custom pragmas on var and let symbols
* add oldast switch for backwards compatibility

5 files changed, 34 insertions, 9 deletions

diff --git a/compiler/ast.nim b/compiler/ast.nim
index 5f5f296cb..24891d6d3 100644
--- a/compiler/ast.nim
+++ b/compiler/ast.nim
@@ -1087,6 +1087,13 @@ proc newSym*(symKind: TSymKind, name: PIdent, owner: PSym,
   when debugIds:
     registerId(result)
 
+proc astdef*(s: PSym): PNode =
+  # get only the definition (initializer) portion of the ast
+  if s.ast != nil and s.ast.kind == nkIdentDefs:
+    s.ast[2]
+  else:
+    s.ast
+
 proc isMetaType*(t: PType): bool =
   return t.kind in tyMetaTypes or
          (t.kind == tyStatic and t.n == nil) or
diff --git a/compiler/commands.nim b/compiler/commands.nim
index 8b73884e8..47687046f 100644
--- a/compiler/commands.nim
+++ b/compiler/commands.nim
@@ -291,6 +291,7 @@ proc testCompileOption*(conf: ConfigRef; switch: string, info: TLineInfo): bool
   of "patterns": result = contains(conf.options, optPatterns)
   of "excessivestacktrace": result = contains(conf.globalOptions, optExcessiveStackTrace)
   of "nilseqs": result = contains(conf.options, optNilSeqs)
+  of "oldast": result = contains(conf.options, optOldAst)
   else: invalidCmdLineOption(conf, passCmd1, switch, info)
 
 proc processPath(conf: ConfigRef; path: string, info: TLineInfo,
@@ -508,6 +509,7 @@ proc processSwitch*(switch, arg: string, pass: TCmdLinePass, info: TLineInfo;
       localError(conf, info, errOnOrOffExpectedButXFound % arg)
   of "laxstrings": processOnOffSwitch(conf, {optLaxStrings}, arg, pass, info)
   of "nilseqs": processOnOffSwitch(conf, {optNilSeqs}, arg, pass, info)
+  of "oldast": processOnOffSwitch(conf, {optOldAst}, arg, pass, info)
   of "checks", "x": processOnOffSwitch(conf, ChecksOptions, arg, pass, info)
   of "floatchecks":
     processOnOffSwitch(conf, {optNaNCheck, optInfCheck}, arg, pass, info)
diff --git a/compiler/guards.nim b/compiler/guards.nim
index a01c023e4..46e18d3bf 100644
--- a/compiler/guards.nim
+++ b/compiler/guards.nim
@@ -257,9 +257,9 @@ proc canon*(n: PNode; o: Operators): PNode =
     for i in 0 ..< n.len:
       result.sons[i] = canon(n.sons[i], o)
   elif n.kind == nkSym and n.sym.kind == skLet and
-      n.sym.ast.getMagic in (someEq + someAdd + someMul + someMin +
+      n.sym.astdef.getMagic in (someEq + someAdd + someMul + someMin +
       someMax + someHigh + {mUnaryLt} + someSub + someLen + someDiv):
-    result = n.sym.ast.copyTree
+    result = n.sym.astdef.copyTree
   else:
     result = n
   case result.getMagic
@@ -395,8 +395,8 @@ proc usefulFact(n: PNode; o: Operators): PNode =
     #   if a:
     #     ...
     # We make can easily replace 'a' by '2 < x' here:
-    if n.sym.ast != nil:
-      result = usefulFact(n.sym.ast, o)
+    if n.sym.astdef != nil:
+      result = usefulFact(n.sym.astdef, o)
   elif n.kind == nkStmtListExpr:
     result = usefulFact(n.lastSon, o)
 
diff --git a/compiler/options.nim b/compiler/options.nim
index 3730d16f8..ea159ee1d 100644
--- a/compiler/options.nim
+++ b/compiler/options.nim
@@ -40,7 +40,8 @@ type                          # please make sure we have under 32 options
     optMemTracker,
     optHotCodeReloading,
     optLaxStrings,
-    optNilSeqs
+    optNilSeqs,
+    optOldAst
 
   TOptions* = set[TOption]
   TGlobalOption* = enum       # **keep binary compatible**
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index 39f200ba8..12283e042 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -330,9 +330,9 @@ proc semIdentDef(c: PContext, n: PNode, kind: TSymKind): PSym =
 proc checkNilable(c: PContext; v: PSym) =
   if {sfGlobal, sfImportC} * v.flags == {sfGlobal} and
       {tfNotNil, tfNeedsInit} * v.typ.flags != {}:
-    if v.ast.isNil:
+    if v.astdef.isNil:
       message(c.config, v.info, warnProveInit, v.name.s)
-    elif tfNotNil in v.typ.flags and tfNotNil notin v.ast.typ.flags:
+    elif tfNotNil in v.typ.flags and tfNotNil notin v.astdef.typ.flags:
       message(c.config, v.info, warnProveInit, v.name.s)
 
 include semasgn
@@ -518,8 +518,6 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
               message(c.config, a.info, warnShadowIdent, v.name.s)
       if a.kind != nkVarTuple:
         if def.kind != nkEmpty:
-          # this is needed for the evaluation pass and for the guard checking:
-          v.ast = def
           if sfThread in v.flags: localError(c.config, def.info, errThreadvarCannotInit)
         setVarType(c, v, typ)
         b = newNodeI(nkIdentDefs, a.info)
@@ -531,6 +529,23 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
         addSon(b, a.sons[length-2])
         addSon(b, copyTree(def))
         addToVarSection(c, result, n, b)
+        if optOldAst in c.config.options:
+          if def.kind != nkEmpty:
+            v.ast = def
+        else:
+          # this is needed for the evaluation pass, guard checking
+          #  and custom pragmas:
+          var ast = newNodeI(nkIdentDefs, a.info)
+          if a[j].kind == nkPragmaExpr:
+            var p = newNodeI(nkPragmaExpr, a.info)
+            p.add newSymNode(v)
+            p.add a[j][1].copyTree
+            ast.add p
+          else:
+            ast.add newSymNode(v)
+          ast.add a.sons[length-2].copyTree
+          ast.add def
+          v.ast = ast
       else:
         if def.kind in {nkPar, nkTupleConstr}: v.ast = def[j]
         # bug #7663, for 'nim check' this can be a non-tuple: