clarify the meaning of the 'auto' metatype; 'auto' is now bind-multiple; fixes #3224

2026-08-27 09:01:37 +00:00 · 2015-09-14 20:25:52 +02:00
parent f79ec6cdf5
commit 0aa908c86c
7 changed files with 91 additions and 55 deletions
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -718,12 +718,12 @@ proc liftParamType(c: PContext, procKind: TSymKind, genericParams: PNode,
  if paramType == nil: return # (e.g. proc return type)

  proc addImplicitGenericImpl(typeClass: PType, typId: PIdent): PType =
-    let finalTypId = if typId != nil: typId
-                     else: getIdent(paramName & ":type")
    if genericParams == nil:
      # This happens with anonymous proc types appearing in signatures
      # XXX: we need to lift these earlier
      return
+    let finalTypId = if typId != nil: typId
+                     else: getIdent(paramName & ":type")
    # is this a bindOnce type class already present in the param list?
    for i in countup(0, genericParams.len - 1):
      if genericParams.sons[i].sym.name.id == finalTypId.id:
@@ -757,7 +757,7 @@ proc liftParamType(c: PContext, procKind: TSymKind, genericParams: PNode,

  case paramType.kind:
  of tyAnything:
-    result = addImplicitGeneric(newTypeS(tyGenericParam, c))
+    result = addImplicitGenericImpl(newTypeS(tyGenericParam, c), nil)

  of tyStatic:
    # proc(a: expr{string}, b: expr{nkLambda})
@@ -868,6 +868,7 @@ proc liftParamType(c: PContext, procKind: TSymKind, genericParams: PNode,
  of tyExpr:
    if procKind notin {skMacro, skTemplate}:
      result = addImplicitGeneric(newTypeS(tyAnything, c))
+      #result = addImplicitGenericImpl(newTypeS(tyGenericParam, c), nil)

  of tyGenericParam:
    markUsed(info, paramType.sym)
@@ -977,7 +978,11 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
    # compiler only checks for 'nil':
    if skipTypes(r, {tyGenericInst}).kind != tyEmpty:
      # 'auto' as a return type does not imply a generic:
-      if r.kind != tyExpr:
+      if r.kind == tyAnything:
+        # 'p(): auto' and 'p(): expr' are equivalent, but the rest of the
+        # compiler is hardly aware of 'auto':
+        r = newTypeS(tyExpr, c)
+      elif r.kind != tyExpr:
        if r.sym == nil or sfAnon notin r.sym.flags:
          let lifted = liftParamType(c, kind, genericParams, r, "result",
                                     n.sons[0].info)
@@ -1346,8 +1351,11 @@ proc processMagicType(c: PContext, m: PSym) =
  of mIntSetBaseType: setMagicType(m, tyRange, intSize)
  of mNil: setMagicType(m, tyNil, ptrSize)
  of mExpr:
-    setMagicType(m, tyExpr, 0)
-    if m.name.s == "expr": m.typ.flags.incl tfOldSchoolExprStmt
+    if m.name.s == "auto":
+      setMagicType(m, tyAnything, 0)
+    else:
+      setMagicType(m, tyExpr, 0)
+      if m.name.s == "expr": m.typ.flags.incl tfOldSchoolExprStmt
  of mStmt:
    setMagicType(m, tyStmt, 0)
    if m.name.s == "stmt": m.typ.flags.incl tfOldSchoolExprStmt
--- a/doc/manual/generics.txt
+++ b/doc/manual/generics.txt
@@ -116,7 +116,7 @@ type class           matches
 ``array``            any array type
 ``set``              any set type
 ``seq``              any seq type
-``auto``             any type
+``any``              any type
 ==================   ===================================================

 Furthermore, every generic type automatically creates a type class of the same
@@ -163,15 +163,6 @@ module to illustrate this:
 Alternatively, the ``distinct`` type modifier can be applied to the type class
 to allow each param matching the type class to bind to a different type.

-If a proc param doesn't have a type specified, Nim will use the
-``distinct auto`` type class (also known as ``any``). Note this behavior is
-deprecated for procs; templates, however, support them:
-
-.. code-block:: nim
-  # allow any combination of param types
-  proc concat(a, b): string = $a & $b # deprecated
-  proc concat(a, b: any): string = $a & $b # preferred
-
 Procs written with the implicitly generic style will often need to refer to the
 type parameters of the matched generic type. They can be easily accessed using
 the dot syntax:
--- a/doc/manual/types.txt
+++ b/doc/manual/types.txt
@@ -1228,3 +1228,27 @@ However, a ``void`` type cannot be inferred in generic code:

 The ``void`` type is only valid for parameters and return types; other symbols
 cannot have the type ``void``.
+
+
+Auto type
+---------
+
+The ``auto`` type can only be used for return types and parameters. For return
+types it causes the compiler to infer the type from the routine body:
+
+.. code-block:: nim
+  proc returnsInt(): auto = 1984
+
+For parameters it currently creates implicitly generic routines:
+
+.. code-block:: nim
+  proc foo(a, b: auto) = discard
+
+Is the same as:
+
+.. code-block:: nim
+  proc foo[T1, T2](a: T1, b: T2) = discard
+
+However later versions of the language might change this to mean "infer the
+parameters' types from the body". Then the above ``foo`` would be rejected as
+the parameters' types can not be infered from an empty ``discard`` statement.
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -78,7 +78,7 @@ type
  stmt* {.magic: Stmt.} ## meta type to denote a statement (for templates)
  typedesc* {.magic: TypeDesc.} ## meta type to denote a type description
  void* {.magic: "VoidType".}   ## meta type to denote the absence of any type
-  auto* = expr ## meta type for automatic type determination
+  auto* {.magic: Expr.} ## meta type for automatic type determination
  any* = distinct auto ## meta type for any supported type
  untyped* {.magic: Expr.} ## meta type to denote an expression that
                           ## is not resolved (for templates)
@@ -104,7 +104,7 @@ type
  SomeNumber* = SomeInteger|SomeReal
    ## type class matching all number types

-proc defined*(x: expr): bool {.magic: "Defined", noSideEffect.}
+proc defined*(x: expr): bool {.magic: "Defined", noSideEffect, compileTime.}
  ## Special compile-time procedure that checks whether `x` is
  ## defined.
  ## `x` is an external symbol introduced through the compiler's
@@ -125,7 +125,7 @@ when defined(nimalias):
    TNumber: SomeNumber,
    TOrdinal: SomeOrdinal].}

-proc declared*(x: expr): bool {.magic: "Defined", noSideEffect.}
+proc declared*(x: expr): bool {.magic: "Defined", noSideEffect, compileTime.}
  ## Special compile-time procedure that checks whether `x` is
  ## declared. `x` has to be an identifier or a qualified identifier.
  ## This can be used to check whether a library provides a certain
@@ -140,11 +140,11 @@ when defined(useNimRtl):
  {.deadCodeElim: on.}

 proc definedInScope*(x: expr): bool {.
-  magic: "DefinedInScope", noSideEffect, deprecated.}
+  magic: "DefinedInScope", noSideEffect, deprecated, compileTime.}
  ## **Deprecated since version 0.9.6**: Use ``declaredInScope`` instead.

 proc declaredInScope*(x: expr): bool {.
-  magic: "DefinedInScope", noSideEffect.}
+  magic: "DefinedInScope", noSideEffect, compileTime.}
  ## Special compile-time procedure that checks whether `x` is
  ## declared in the current scope. `x` has to be an identifier.

@@ -160,7 +160,7 @@ proc unsafeAddr*[T](x: var T): ptr T {.magic: "Addr", noSideEffect.} =
  ## Cannot be overloaded.
  discard

-proc `type`*(x: expr): typeDesc {.magic: "TypeOf", noSideEffect.} =
+proc `type`*(x: expr): typeDesc {.magic: "TypeOf", noSideEffect, compileTime.} =
  ## Builtin 'type' operator for accessing the type of an expression.
  ## Cannot be overloaded.
  discard
@@ -3392,7 +3392,7 @@ when hasAlloc:
      x[j+i] = item[j]
      inc(j)

-proc compiles*(x: expr): bool {.magic: "Compiles", noSideEffect.} =
+proc compiles*(x: expr): bool {.magic: "Compiles", noSideEffect, compileTime.} =
  ## Special compile-time procedure that checks whether `x` can be compiled
  ## without any semantic error.
  ## This can be used to check whether a type supports some operation:
@@ -3456,7 +3456,7 @@ when hasAlloc and not defined(nimscript) and not defined(JS):

  include "system/deepcopy"

-proc procCall*(x: expr) {.magic: "ProcCall".} =
+proc procCall*(x: expr) {.magic: "ProcCall", compileTime.} =
  ## special magic to prohibit dynamic binding for `method`:idx: calls.
  ## This is similar to `super`:idx: in ordinary OO languages.
  ##
--- a/tests/metatype/ttypedesc1.nim
+++ b/tests/metatype/ttypedesc1.nim
@@ -7,7 +7,7 @@ type

 proc getTypeName(t: typedesc): string = t.name

-proc foo(T: typedesc[float], a: expr): string =
+proc foo(T: typedesc[float], a: auto): string =
  result = "float " & $(a.len > 5)

 proc foo(T: typedesc[TFoo], a: int): string =
--- a/tests/types/tauto_excessive.nim
+++ b/tests/types/tauto_excessive.nim
@@ -0,0 +1,20 @@
+discard """
+  output: '''10
+10.0
+1.0hiho'''
+"""
+
+# bug #3224
+proc f(x: auto): auto =
+  result = $(x+10)
+
+proc f(x, y: auto): auto =
+  result = $(x+y)
+
+
+echo f(0)     # prints 10
+echo f(0.0)  # prints 10.0
+
+proc `+`(a, b: string): string = a & b
+
+echo f(0.7, 0.3), f("hi", "ho")
--- a/web/news.txt
+++ b/web/news.txt
@@ -3,7 +3,7 @@ News
 ====

 ..
-  2015-05-05 Version 0.11.4 released
+  2015-09-14 Version 0.11.4 released
  ==================================

  Changes affecting backwards compatibility
@@ -58,7 +58,7 @@ News
    of all the DLLs the standard library needs. This means that the following
    DLLs are now split into 32 and 64 versions:

-    * ``prce.dll``: Split into ``prce32.dll`` and ``prce64.dll``.
+    * ``pcre.dll``: Split into ``pcre32.dll`` and ``pcre64.dll``.
    * ``pdcurses.dll``: Split into ``pdcurses32.dll`` and ``pdcurses64.dll``.
    * ``sqlite3.dll``: Split into ``sqlite3_32.dll`` and ``sqlite3_64.dll``.
    * ``ssleay32.dll``: Split into ``ssleay32.dll`` and ``ssleay64.dll``.
@@ -75,6 +75,13 @@ News
    with Unix's ``#!``.
  - An implicit return type for an iterator is now deprecated. Use ``auto`` if
    you want more type inference.
+  - The type ``auto`` is now a "multi-bind" metatype, so the following compiles:
+
+    .. code-block:: nim
+      proc f(x, y: auto): auto =
+        result = $x & y
+
+      echo f(0, "abc")


  Library Additions
@@ -116,24 +123,20 @@ News
  - ``when nimvm`` can now be used for compiletime versions of some code
    sections. Click `here <docs/manual.html#when-nimvm-statement>`_ for details.
  - Usage of the type ``NimNode`` in a proc now implicitly annotates the proc
-    with ``.compileTime``. This means generics work much better
-    for ``NimNode``.
+    with ``.compileTime``. This means generics work much better for ``NimNode``.


  Bugfixes
  --------
-  - Fixed "Compiler internal error on iterator it(T: typedesc[Base]) called with
- it(Child), where Child = object of Base"
+  - Fixed "Compiler internal error on iterator it(T: typedesc[Base]) called with it(Child), where Child = object of Base"
    (`#2662 <https://github.com/Araq/Nim/issues/2662>`_)
  - Fixed "repr() misses base object field in 2nd level derived object"
    (`#2749 <https://github.com/Araq/Nim/issues/2749>`_)
  - Fixed "nimsuggest doesn't work more than once on the non-main file"
    (`#2694 <https://github.com/Araq/Nim/issues/2694>`_)
-  - Fixed "JS Codegen. Passing arguments by var in certain cases leads to invali
-d JS."
+  - Fixed "JS Codegen. Passing arguments by var in certain cases leads to invalid JS."
    (`#2798 <https://github.com/Araq/Nim/issues/2798>`_)
-  - Fixed ""check" proc in unittest.nim prevents the propagation of changes to v
-ar parameters."
+  - Fixed ""check" proc in unittest.nim prevents the propagation of changes to var parameters."
    (`#964 <https://github.com/Araq/Nim/issues/964>`_)
  - Fixed "Excessive letters in integer literals are not an error"
    (`#2523 <https://github.com/Araq/Nim/issues/2523>`_)
@@ -147,8 +150,7 @@ ar parameters."
    (`#2687 <https://github.com/Araq/Nim/issues/2687>`_)
  - Fixed "Compile error using object in const array"
    (`#2774 <https://github.com/Araq/Nim/issues/2774>`_)
-  - Fixed "httpclient async requests with method httpPOST isn't sending Content-
-Length header"
+  - Fixed "httpclient async requests with method httpPOST isn't sending Content-Length header"
    (`#2884 <https://github.com/Araq/Nim/issues/2884>`_)
  - Fixed "Streams module not working with JS backend"
    (`#2148 <https://github.com/Araq/Nim/issues/2148>`_)
@@ -179,8 +181,7 @@ Length header"
    (`#2974 <https://github.com/Araq/Nim/issues/2974>`_)
  - Fixed "repr is broken"
    (`#2992 <https://github.com/Araq/Nim/issues/2992>`_)
-  - Fixed "Ipv6 devel - add IPv6 support for asyncsockets, make AF_INET6 a defau
-lt"
+  - Fixed "Ipv6 devel - add IPv6 support for asyncsockets, make AF_INET6 a default"
    (`#2976 <https://github.com/Araq/Nim/issues/2976>`_)
  - Fixed "Compilation broken on windows"
    (`#2996 <https://github.com/Araq/Nim/issues/2996>`_)
@@ -190,8 +191,7 @@ lt"
    (`#2672 <https://github.com/Araq/Nim/issues/2672>`_)
  - Fixed "Uncatched exception in async procedure on raise statement"
    (`#3014 <https://github.com/Araq/Nim/issues/3014>`_)
-  - Fixed "nim doc2 fails in Mac OS X due to system.nim (possibly related to #18
-98)"
+  - Fixed "nim doc2 fails in Mac OS X due to system.nim (possibly related to #1898)"
    (`#3005 <https://github.com/Araq/Nim/issues/3005>`_)
  - Fixed "IndexError when rebuilding Nim on iteration 2"
    (`#3018 <https://github.com/Araq/Nim/issues/3018>`_)
@@ -239,8 +239,7 @@ lt"
    (`#3054 <https://github.com/Araq/Nim/issues/3054>`_)
  - Fixed "Wrong sharing of static_t instantations"
    (`#3112 <https://github.com/Araq/Nim/issues/3112>`_)
-  - Fixed "Automatically generated proc conflicts with user-defined proc when .e
-xportc.'ed"
+  - Fixed "Automatically generated proc conflicts with user-defined proc when .exportc.'ed"
    (`#3134 <https://github.com/Araq/Nim/issues/3134>`_)
  - Fixed "getTypeInfo call crashes nim"
    (`#3099 <https://github.com/Araq/Nim/issues/3099>`_)
@@ -260,15 +259,13 @@ xportc.'ed"
    (`#3149 <https://github.com/Araq/Nim/issues/3149>`_)
  - Fixed "Inference of `static[T]` in sequences"
    (`#3144 <https://github.com/Araq/Nim/issues/3144>`_)
-  - Fixed "Argument named "closure" to proc inside template interfere with closu
-re pragma"
+  - Fixed "Argument named "closure" to proc inside template interfere with closure pragma"
    (`#3171 <https://github.com/Araq/Nim/issues/3171>`_)
  - Fixed "Internal error with aliasing inside template"
    (`#3158 <https://github.com/Araq/Nim/issues/3158>`_)
  - Fixed "Cardinality of sets prints unexpected value"
    (`#3135 <https://github.com/Araq/Nim/issues/3135>`_)
-  - Fixed "Nim crashes on const assignment from function returning var ref objec
-t"
+  - Fixed "Nim crashes on const assignment from function returning var ref object"
    (`#3103 <https://github.com/Araq/Nim/issues/3103>`_)
  - Fixed "`repr` cstring"
    (`#3080 <https://github.com/Araq/Nim/issues/3080>`_)
@@ -276,8 +273,7 @@ t"
    (`#3052 <https://github.com/Araq/Nim/issues/3052>`_)
  - Fixed "Compiler assertion when evaluating template with static[T]"
    (`#1858 <https://github.com/Araq/Nim/issues/1858>`_)
-  - Fixed "Erroneous overflow in iterators when compiler built with overflowChec
-ks enabled"
+  - Fixed "Erroneous overflow in iterators when compiler built with overflowChecks enabled"
    (`#3140 <https://github.com/Araq/Nim/issues/3140>`_)
  - Fixed "Unicode dashes as "lisp'ish" alternative to hump and snake notation"
    (`#2811 <https://github.com/Araq/Nim/issues/2811>`_)
@@ -289,8 +285,7 @@ ks enabled"
    (`#3193 <https://github.com/Araq/Nim/issues/3193>`_)
  - Fixed "VM crash when accessing array's element"
    (`#3192 <https://github.com/Araq/Nim/issues/3192>`_)
-  - Fixed "Unexpected proc invoked when different modules add procs to a type fr
-om a 3rd module"
+  - Fixed "Unexpected proc invoked when different modules add procs to a type from a 3rd module"
    (`#2664 <https://github.com/Araq/Nim/issues/2664>`_)
  - Fixed "Nim crashes on conditional declaration inside a template"
    (`#2670 <https://github.com/Araq/Nim/issues/2670>`_)
@@ -298,8 +293,7 @@ om a 3rd module"
    (`#2752 <https://github.com/Araq/Nim/issues/2752>`_)
  - Fixed "VM: Cannot assign int value to ref variable"
    (`#1329 <https://github.com/Araq/Nim/issues/1329>`_)
-  - Fixed "Incorrect code generated for tagged unions with enums not starting at
- zero"
+  - Fixed "Incorrect code generated for tagged unions with enums not starting at zero"
    (`#3096 <https://github.com/Araq/Nim/issues/3096>`_)
  - Fixed "Compile time procs using forward declarations are silently ignored"
    (`#3066 <https://github.com/Araq/Nim/issues/3066>`_)
@@ -307,8 +301,7 @@ om a 3rd module"
    (`#1965 <https://github.com/Araq/Nim/issues/1965>`_)
  - Fixed "os.getCreationTime is incorrect/impossible on Posix systems"
    (`#1058 <https://github.com/Araq/Nim/issues/1058>`_)
-  - Fixed "Improve error message for osproc.startProcess when command does not e
-xist"
+  - Fixed "Improve error message for osproc.startProcess when command does not exist"
    (`#2183 <https://github.com/Araq/Nim/issues/2183>`_)
  - Fixed "gctest segfaults with --gc:markandsweep on x86_64"
    (`#2305 <https://github.com/Araq/Nim/issues/2305>`_)