fix: var a{.foo.} = expr inside templates (refs #15920) (except when foo is overloaded) (#13869)

* fix: `var a{.foo.} = expr` inside templates
* add test
* improve tdecls test
* improve tests
* add failing test
* PRTEMP
* fixup

tests/pragmas/tpragmas_misc.nim

@@ -10,3 +10,55 @@ block:
   static: doAssert defined(tpragmas_misc_def)
   {.undef(tpragmas_misc_def).}
   static: doAssert not defined(tpragmas_misc_def)
+
+block: # (partial fix) bug #15920
+  block: # var template pragmas don't work in templates
+    template foo(lhs, typ, expr) =
+      let lhs = expr
+    proc fun1()=
+      let a {.foo.} = 1
+    template fun2()=
+      let a {.foo.} = 1
+    fun1() # ok
+    fun2() # WAS bug
+
+  template foo2() = discard # distractor (template or other symbol kind)
+  block:
+    template foo2(lhs, typ, expr) =
+      let lhs = expr
+    proc fun1()=
+      let a {.foo2.} = 1
+    template fun2()=
+      let a {.foo2.} = 1
+    fun1() # ok
+    when false: # bug: Error: invalid pragma: foo2
+      fun2()
+
+  block: # proc template pragmas don't work in templates
+    # adapted from $nim/lib/std/private/since.nim
+    # case without overload
+    template since3(version: (int, int), body: untyped) {.dirty.} =
+      when (NimMajor, NimMinor) >= version:
+        body
+    when false: # bug
+      template fun3(): int {.since3: (1, 3).} = 12
+
+  block: # ditto, w
+    # case with overload
+    template since2(version: (int, int), body: untyped) {.dirty.} =
+      when (NimMajor, NimMinor) >= version:
+        body
+    template since2(version: (int, int, int), body: untyped) {.dirty.} =
+      when (NimMajor, NimMinor, NimPatch) >= version:
+        body
+    when false: # bug
+      template fun3(): int {.since2: (1, 3).} = 12
+
+when true: # D20210801T100514:here
+  from macros import genSym
+  block:
+    template fn() =
+      var ret {.gensym.}: int # must special case template pragmas so it doesn't get confused
+      discard ret
+    fn()
+    static: discard genSym()

tests/stdlib/tdecls.nim

@@ -1,6 +1,10 @@
+discard """
+  targets: "c cpp js"
+"""
+
 import std/decls
 
-block:
+template fun() =
   var s = @[10,11,12]
   var a {.byaddr.} = s[0]
   a+=100
@@ -34,6 +38,13 @@ block:
   doAssert compiles(block:
     var b2 {.byaddr.}: int = s[2])
 
+proc fun2() = fun()
+fun()
+fun2()
+static: fun2()
+when false: # pending bug #13887
+  static: fun()
+
 ## We can define custom pragmas in user code
 template byUnsafeAddr(lhs, typ, expr) =
   when typ is type(nil):
@@ -68,3 +79,13 @@ block: # nkAccQuoted
     let a {.`cast`.} = s[0]
     doAssert a == "foo"
     doAssert a[0].unsafeAddr == s[0][0].unsafeAddr
+
+block: # bug #15920
+  template foo(lhs, typ, expr) =
+    let lhs = expr
+  proc fun1()=
+    let a {.foo.} = 1
+  template fun2()=
+    let a {.foo.} = 1
+  fun1() # ok
+  fun2() # BUG

tests/stdlib/tsince.nim

@@ -27,6 +27,6 @@ since (99, 3):
   doAssert false
 
 when false:
-  # pending https://github.com/timotheecour/Nim/issues/129
+  # pending bug #15920
   # Error: cannot attach a custom pragma to 'fun3'
   template fun3(): int {.since: (1, 3).} = 12