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

changelog.md

@@ -23,7 +23,8 @@
 - The undocumented ``#? strongSpaces`` parsing mode has been removed.
 - The `not` operator is now always a unary operator, this means that code like
   ``assert not isFalse(3)`` compiles.
-
+- `getImpl` on a `var` or `let` symbol will now return the full `IdentDefs`
+  tree from the symbol declaration instead of just the initializer portion.
 
 #### Breaking changes in the standard library
 
@@ -133,8 +134,9 @@ proc enumToString*(enums: openArray[enum]): string =
   the `gcsafe` pragma block.
 - added os.getCurrentProcessId()
 - User defined pragmas are now allowed in the pragma blocks
-- Pragma blocks are now longer eliminated from the typed AST tree to preserve
+- Pragma blocks are no longer eliminated from the typed AST tree to preserve
   pragmas for further analysis by macros
+- Custom pragmas are now supported for `var` and `let` symbols.
 
 ### Language changes
 

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

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)

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:
+    if n.sym.astdef != nil:
-      result = usefulFact(n.sym.ast, o)
+      result = usefulFact(n.sym.astdef, o)
   elif n.kind == nkStmtListExpr:
     result = usefulFact(n.lastSon, o)
 

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**

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:

doc/advopt.txt

@@ -76,6 +76,7 @@ Advanced options:
                             strings is allowed; only for backwards compatibility
   --nilseqs:on|off          allow 'nil' for strings/seqs for
                             backwards compatibility
+  --oldast:on|off           use old AST for backwards compatibility
   --skipCfg                 do not read the general configuration file
   --skipUserCfg             do not read the user's configuration file
   --skipParentCfg           do not read the parent dirs' configuration files

lib/core/macros.nim

@@ -1402,8 +1402,14 @@ proc customPragmaNode(n: NimNode): NimNode =
     let impl = n.getImpl()
     if impl.kind in RoutineNodes:
       return impl.pragma
+    elif impl.kind == nnkIdentDefs and impl[0].kind == nnkPragmaExpr:
+      return impl[0][1]
     else:
-      return typ.getImpl()[0][1]
+      let timpl = typ.getImpl()
+      if timpl.len>0 and timpl[0].len>1:
+        return timpl[0][1]
+      else:
+        return timpl
 
   if n.kind in {nnkDotExpr, nnkCheckedFieldExpr}:
     let name = $(if n.kind == nnkCheckedFieldExpr: n[0][1] else: n[1])

tests/pragmas/tcustom_pragma.nim

@@ -175,7 +175,6 @@ var foo: Something
 foo.cardinal = north
 doAssert foo.b.hasCustomPragma(thingy) == true
 
-
 proc myproc(s: string): int =
   {.thingy.}:
     s.len
@@ -188,7 +187,6 @@ let xx = compiles:
       s.len
 doAssert: xx == false
 
-
 macro checkSym(s: typed{nkSym}): untyped =
   let body = s.getImpl.body
   doAssert body[1].kind == nnkPragmaBlock
@@ -196,3 +194,28 @@ macro checkSym(s: typed{nkSym}): untyped =
   doAssert body[1][0][0] == bindSym"thingy"
 
 checkSym(myproc)
+
+# var and let pragmas
+block:
+  template myAttr() {.pragma.}
+  template myAttr2(x: int) {.pragma.}
+  template myAttr3(x: string) {.pragma.}
+
+  let a {.myAttr,myAttr2(2),myAttr3:"test".}: int = 0
+  let b {.myAttr,myAttr2(2),myAttr3:"test".} = 0
+  var x {.myAttr,myAttr2(2),myAttr3:"test".}: int = 0
+  var y {.myAttr,myAttr2(2),myAttr3:"test".}: int
+  var z {.myAttr,myAttr2(2),myAttr3:"test".} = 0
+
+  template check(s: untyped) =
+    doAssert s.hasCustomPragma(myAttr)
+    doAssert s.hasCustomPragma(myAttr2)
+    doAssert s.getCustomPragmaVal(myAttr2) == 2
+    doAssert s.hasCustomPragma(myAttr3)
+    doAssert s.getCustomPragmaVal(myAttr3) == "test"
+
+  check(a)
+  check(b)
+  check(x)
+  check(y)
+  check(z)