deprecate the .this pragma

changelog.md

@@ -170,6 +170,10 @@
 - Nim now supports ``except`` clause in the export statement.
 
 - Range float types, example ``range[0.0 .. Inf]``. More details in language manual.
+- The ``{.this.}`` pragma has been deprecated. It never worked within generics and
+  we found the resulting code harder to read than the more explicit ``obj.field``
+  syntax.
+
 
 ### Tool changes
 

compiler/idents.nim

@@ -30,14 +30,7 @@ type
     wordCounter: int
     idAnon*, idDelegator*, emptyIdent*: PIdent
 
-when false:
-  var
-    legacy: IdentCache
-
-proc resetIdentCache*() =
-  when false:
-    for i in low(legacy.buckets)..high(legacy.buckets):
-      legacy.buckets[i] = nil
+proc resetIdentCache*() = discard
 
 proc cmpIgnoreStyle*(a, b: cstring, blen: int): int =
   if a[0] != b[0]: return 1
@@ -73,11 +66,9 @@ proc cmpExact(a, b: cstring, blen: int): int =
   if result == 0:
     if a[i] != '\0': result = 1
 
-{.this: self.}
-
-proc getIdent*(self: IdentCache; identifier: cstring, length: int, h: Hash): PIdent =
-  var idx = h and high(buckets)
-  result = buckets[idx]
+proc getIdent*(ic: IdentCache; identifier: cstring, length: int, h: Hash): PIdent =
+  var idx = h and high(ic.buckets)
+  result = ic.buckets[idx]
   var last: PIdent = nil
   var id = 0
   while result != nil:
@@ -85,8 +76,8 @@ proc getIdent*(self: IdentCache; identifier: cstring, length: int, h: Hash): PId
       if last != nil:
         # make access to last looked up identifier faster:
         last.next = result.next
-        result.next = buckets[idx]
-        buckets[idx] = result
+        result.next = ic.buckets[idx]
+        ic.buckets[idx] = result
       return
     elif cmpIgnoreStyle(cstring(result.s), identifier, length) == 0:
       assert((id == 0) or (id == result.id))
@@ -97,20 +88,20 @@ proc getIdent*(self: IdentCache; identifier: cstring, length: int, h: Hash): PId
   result.h = h
   result.s = newString(length)
   for i in countup(0, length - 1): result.s[i] = identifier[i]
-  result.next = buckets[idx]
-  buckets[idx] = result
+  result.next = ic.buckets[idx]
+  ic.buckets[idx] = result
   if id == 0:
-    inc(wordCounter)
-    result.id = -wordCounter
+    inc(ic.wordCounter)
+    result.id = -ic.wordCounter
   else:
     result.id = id
 
-proc getIdent*(self: IdentCache; identifier: string): PIdent =
-  result = getIdent(cstring(identifier), len(identifier),
+proc getIdent*(ic: IdentCache; identifier: string): PIdent =
+  result = getIdent(ic, cstring(identifier), len(identifier),
                     hashIgnoreStyle(identifier))
 
-proc getIdent*(self: IdentCache; identifier: string, h: Hash): PIdent =
-  result = getIdent(cstring(identifier), len(identifier), h)
+proc getIdent*(ic: IdentCache; identifier: string, h: Hash): PIdent =
+  result = getIdent(ic, cstring(identifier), len(identifier), h)
 
 proc newIdentCache*(): IdentCache =
   result = IdentCache()

compiler/modulegraphs.nim

@@ -65,10 +65,8 @@ type
 
 proc hash*(x: FileIndex): Hash {.borrow.}
 
-{.this: g.}
-
 proc stopCompile*(g: ModuleGraph): bool {.inline.} =
-  result = doStopCompile != nil and doStopCompile()
+  result = g.doStopCompile != nil and g.doStopCompile()
 
 proc createMagic*(g: ModuleGraph; name: string, m: TMagic): PSym =
   result = newSym(skProc, getIdent(g.cache, name), nil, unknownLineInfo(), {})
@@ -98,44 +96,44 @@ proc newModuleGraph*(cache: IdentCache; config: ConfigRef): ModuleGraph =
   result.cacheTables = initTable[string, BTree[string, PNode]]()
 
 proc resetAllModules*(g: ModuleGraph) =
-  initStrTable(packageSyms)
-  deps = initIntSet()
-  modules = @[]
-  importStack = @[]
-  inclToMod = initTable[FileIndex, FileIndex]()
-  usageSym = nil
-  owners = @[]
-  methods = @[]
-  initStrTable(compilerprocs)
-  initStrTable(exposed)
+  initStrTable(g.packageSyms)
+  g.deps = initIntSet()
+  g.modules = @[]
+  g.importStack = @[]
+  g.inclToMod = initTable[FileIndex, FileIndex]()
+  g.usageSym = nil
+  g.owners = @[]
+  g.methods = @[]
+  initStrTable(g.compilerprocs)
+  initStrTable(g.exposed)
 
 proc getModule*(g: ModuleGraph; fileIdx: FileIndex): PSym =
-  if fileIdx.int32 >= 0 and fileIdx.int32 < modules.len:
-    result = modules[fileIdx.int32]
+  if fileIdx.int32 >= 0 and fileIdx.int32 < g.modules.len:
+    result = g.modules[fileIdx.int32]
 
 proc dependsOn(a, b: int): int {.inline.} = (a shl 15) + b
 
 proc addDep*(g: ModuleGraph; m: PSym, dep: FileIndex) =
   assert m.position == m.info.fileIndex.int32
   addModuleDep(g.incr, g.config, m.info.fileIndex, dep, isIncludeFile = false)
-  if suggestMode:
-    deps.incl m.position.dependsOn(dep.int)
+  if g.suggestMode:
+    g.deps.incl m.position.dependsOn(dep.int)
     # we compute the transitive closure later when quering the graph lazily.
     # this improves efficiency quite a lot:
     #invalidTransitiveClosure = true
 
 proc addIncludeDep*(g: ModuleGraph; module, includeFile: FileIndex) =
   addModuleDep(g.incr, g.config, module, includeFile, isIncludeFile = true)
-  discard hasKeyOrPut(inclToMod, includeFile, module)
+  discard hasKeyOrPut(g.inclToMod, includeFile, module)
 
 proc parentModule*(g: ModuleGraph; fileIdx: FileIndex): FileIndex =
   ## returns 'fileIdx' if the file belonging to this index is
   ## directly used as a module or else the module that first
   ## references this include file.
-  if fileIdx.int32 >= 0 and fileIdx.int32 < modules.len and modules[fileIdx.int32] != nil:
+  if fileIdx.int32 >= 0 and fileIdx.int32 < g.modules.len and g.modules[fileIdx.int32] != nil:
     result = fileIdx
   else:
-    result = inclToMod.getOrDefault(fileIdx)
+    result = g.inclToMod.getOrDefault(fileIdx)
 
 proc transitiveClosure(g: var IntSet; n: int) =
   # warshall's algorithm
@@ -147,22 +145,22 @@ proc transitiveClosure(g: var IntSet; n: int) =
             g.incl i.dependsOn(j)
 
 proc markDirty*(g: ModuleGraph; fileIdx: FileIndex) =
-  let m = getModule fileIdx
+  let m = g.getModule fileIdx
   if m != nil: incl m.flags, sfDirty
 
 proc markClientsDirty*(g: ModuleGraph; fileIdx: FileIndex) =
   # we need to mark its dependent modules D as dirty right away because after
   # nimsuggest is done with this module, the module's dirty flag will be
   # cleared but D still needs to be remembered as 'dirty'.
-  if invalidTransitiveClosure:
-    invalidTransitiveClosure = false
-    transitiveClosure(deps, modules.len)
+  if g.invalidTransitiveClosure:
+    g.invalidTransitiveClosure = false
+    transitiveClosure(g.deps, g.modules.len)
 
   # every module that *depends* on this file is also dirty:
-  for i in 0i32..<modules.len.int32:
-    let m = modules[i]
-    if m != nil and deps.contains(i.dependsOn(fileIdx.int)):
+  for i in 0i32..<g.modules.len.int32:
+    let m = g.modules[i]
+    if m != nil and g.deps.contains(i.dependsOn(fileIdx.int)):
       incl m.flags, sfDirty
 
 proc isDirty*(g: ModuleGraph; m: PSym): bool =
-  result = suggestMode and sfDirty in m.flags
+  result = g.suggestMode and sfDirty in m.flags

compiler/pragmas.nim

@@ -1066,8 +1066,10 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: var int,
       of wThis:
         if it.kind in nkPragmaCallKinds and it.len == 2:
           c.selfName = considerQuotedIdent(c, it[1])
+          message(c.config, n.info, warnDeprecated, "the '.this' pragma")
         elif it.kind == nkIdent or it.len == 1:
           c.selfName = getIdent(c.cache, "self")
+          message(c.config, n.info, warnDeprecated, "the '.this' pragma")
         else:
           localError(c.config, it.info, "'this' pragma is allowed to have zero or one arguments")
       of wNoRewrite:

doc/manual.rst

@@ -2336,6 +2336,8 @@ pointer type and overloading resolution is tried with ``a[]`` instead.
 Automatic self insertions
 -------------------------
 
+**Note**: The ``.this`` pragma is deprecated and should not be used anymore.
+
 Starting with version 0.14 of the language, Nim supports ``field`` as a
 shortcut for ``self.field`` comparable to the `this`:idx: keyword in Java
 or C++. This feature has to be explicitly enabled via a ``{.this: self.}``