experimental switch for generic compileTime, remove typeof behavior

fixes nim-lang#24228, refs nim-lang#22022

compiler/options.nim

@@ -228,6 +228,7 @@ type
     openSym, # remove nfDisabledOpenSym when this is default
     # alternative to above:
     genericsOpenSym
+    genericProcCompileTime
     vtables
 
   LegacyFeature* = enum

compiler/semdata.nim

@@ -171,7 +171,6 @@ type
     inUncheckedAssignSection*: int
     importModuleLookup*: Table[int, seq[int]] # (module.ident.id, [module.id])
     skipTypes*: seq[PNode] # used to skip types between passes in type section. So far only used for inheritance, sets and generic bodies.
-    inTypeofContext*: int
   TBorrowState* = enum
     bsNone, bsReturnNotMatch, bsNoDistinct, bsGeneric, bsNotSupported, bsMatch
 

compiler/semexprs.nim

@@ -995,8 +995,11 @@ proc evalAtCompileTime(c: PContext, n: PNode): PNode =
 
     if callee.magic notin ctfeWhitelist: return
 
-    if callee.kind notin {skProc, skFunc, skConverter, skConst} or
-        callee.isGenericRoutineStrict:
+    if callee.kind notin {skProc, skFunc, skConverter, skConst} or (
+        if genericProcCompileTime in c.features:
+          callee.isGenericRoutineStrict
+        else:
+          callee.isGenericRoutine):
       return
 
     if n.typ != nil and typeAllowed(n.typ, skConst, c) != nil: return
@@ -1136,7 +1139,7 @@ proc afterCallActions(c: PContext; n, orig: PNode, flags: TExprFlags; expectedTy
           not (result.typ.kind == tySequence and result.elementType.kind == tyEmpty):
         liftTypeBoundOps(c, result.typ, n.info)
     #result = patchResolvedTypeBoundOp(c, result)
-  if c.matchedConcept == nil and (c.inTypeofContext == 0 or callee.magic != mNone):
+  if c.matchedConcept == nil:
     # don't fold calls in concepts and typeof
     result = evalAtCompileTime(c, result)
 

compiler/semmagic.nim

@@ -49,8 +49,6 @@ proc semTypeOf(c: PContext; n: PNode): PNode =
     else:
       m = mode.intVal
   result = newNodeI(nkTypeOfExpr, n.info)
-  inc c.inTypeofContext
-  defer: dec c.inTypeofContext # compiles can raise an exception
   let typExpr = semExprWithType(c, n[1], if m == 1: {efInTypeof} else: {})
   result.add typExpr
   if typExpr.typ.kind == tyFromExpr:

compiler/semtypes.nim

@@ -1870,8 +1870,6 @@ proc semStaticType(c: PContext, childNode: PNode, prev: PType): PType =
 
 proc semTypeOf(c: PContext; n: PNode; prev: PType): PType =
   openScope(c)
-  inc c.inTypeofContext
-  defer: dec c.inTypeofContext # compiles can raise an exception
   let t = semExprWithType(c, n, {efInTypeof})
   closeScope(c)
   fixupTypeOf(c, prev, t)
@@ -1888,8 +1886,6 @@ proc semTypeOf2(c: PContext; n: PNode; prev: PType): PType =
       localError(c.config, n.info, "typeof: cannot evaluate 'mode' parameter at compile-time")
     else:
       m = mode.intVal
-  inc c.inTypeofContext
-  defer: dec c.inTypeofContext # compiles can raise an exception
   let t = semExprWithType(c, n[1], if m == 1: {efInTypeof} else: {})
   closeScope(c)
   fixupTypeOf(c, prev, t)

tests/vm/tgenericcompiletimeproc.nim

@@ -1,3 +1,15 @@
+block:
+  # don't fold compile time procs in typeof with experimental switch disabled
+  proc fail[T](x: T): T {.compileTime.} =
+    doAssert false
+    x
+  doAssert typeof(fail(123)) is typeof(123)
+  proc p(x: int): int = x
+
+  type Foo = typeof(p(fail(123)))
+
+{.experimental: "genericProcCompileTime".}
+
 block: # issue #10753
   proc foo(x: int): int {.compileTime.} = x
   const a = foo(123)
@@ -18,16 +30,6 @@ block: # issue #19365
   doAssert f(123) == 246
   doAssert f(1.0) == 2.0
 
-block:
-  # don't fold compile time procs in typeof
-  proc fail[T](x: T): T {.compileTime.} =
-    doAssert false
-    x
-  doAssert typeof(fail(123)) is typeof(123)
-  proc p(x: int): int = x
-
-  type Foo = typeof(p(fail(123)))
-
 block: # issue #24150, related regression
   proc w(T: type): T {.compileTime.} = default(ptr T)[]
   template y(v: auto): auto = typeof(v) is int