=> supports pragmas & names (+ changed behavior) (nim-lang#14200)

* => supports pragmas & names (+ changed behavior)

(x, y: int) is now parsed as (x: int, y: int) instead of
(x: auto, y: int) inside => and ->.

* fix pragma check

* fixes, use since & LHS of -> supports pragmas

changelog.md

@@ -61,6 +61,22 @@
 - `paramCount` & `paramStr` are now defined in os.nim instead of nimscript.nim for nimscript/nimble.
 - `dollars.$` now works for unsigned ints with `nim js`
 
+- `sugar.=>` and `sugar.->` changes: Previously `(x, y: int)` was transformed
+  into `(x: auto, y: int)`, it now becomes `(x: int, y: int)` in consistency
+  with regular proc definitions (although you cannot use semicolons).
+
+  Pragmas and using a name are now allowed on the lefthand side of `=>`. Here
+  is an aggregate example of these changes:
+  ```nim
+  import sugar
+
+  foo(x, y: int) {.noSideEffect.} => x + y
+
+  # is transformed into
+
+  proc foo(x: int, y: int): auto {.noSideEffect.} = x + y
+  ```
+
 ## Language changes
 - In newruntime it is now allowed to assign discriminator field without restrictions as long as case object doesn't have custom destructor. Discriminator value doesn't have to be a constant either. If you have custom destructor for case object and you do want to freely assign discriminator fields, it is recommended to refactor object into 2 objects like this:
   ```nim

lib/pure/htmlgen.nim

@@ -64,7 +64,7 @@ proc getIdent(e: NimNode): string {.compileTime.} =
     result = getIdent(e[0])
     for i in 1 .. e.len-1:
       result.add getIdent(e[i])
-  else: error("cannot extract identifier from node: " & toStrLit(e).strVal)
+  else: error("cannot extract identifier from node: " & toStrLit(e).strVal, e)
 
 proc delete[T](s: var seq[T], attr: T): bool =
   var idx = find(s, attr)
@@ -96,14 +96,14 @@ proc xmlCheckedTag*(argsList: NimNode, tag: string, optAttr = "", reqAttr = "",
         result.add(argsList[i][1])
         result.add(newStrLitNode("\""))
       else:
-        error("invalid attribute for '" & tag & "' element: " & name)
+        error("invalid attribute for '" & tag & "' element: " & name, argsList[i])
   # check each required attribute exists:
   if req.len > 0:
-    error(req[0] & " attribute for '" & tag & "' element expected")
+    error(req[0] & " attribute for '" & tag & "' element expected", argsList)
   if isLeaf:
     for i in 0 ..< argsList.len:
       if argsList[i].kind != nnkExprEqExpr:
-        error("element " & tag & " cannot be nested")
+        error("element " & tag & " cannot be nested", argsList[i])
     result.add(newStrLitNode(" />"))
   else:
     result.add(newStrLitNode(">"))

lib/pure/strutils.nim

@@ -1295,7 +1295,7 @@ macro genEnumStmt(typ: typedesc, argSym: typed, default: typed): untyped =
       foundFields.add fStr
     else:
       error("Ambiguous enums cannot be parsed, field " & $fStr &
-        " appears multiple times!")
+        " appears multiple times!", f)
     inc fNum
   # finally add else branch to raise or use default
   if default == nil:

lib/pure/sugar.nim

@@ -11,16 +11,25 @@
 ## macro system.
 
 import std/private/since
-import macros
-import typetraits
+import macros, typetraits
+
+proc checkPragma(ex, prag: var NimNode) =
+  since (1, 3):
+    if ex.kind == nnkPragmaExpr:
+      prag = ex[1]
+      if ex[0].kind == nnkPar and ex[0].len == 1:
+        ex = ex[0][0]
+      else:
+        ex = ex[0]
 
 proc createProcType(p, b: NimNode): NimNode {.compileTime.} =
-  #echo treeRepr(p)
-  #echo treeRepr(b)
   result = newNimNode(nnkProcTy)
-  var formalParams = newNimNode(nnkFormalParams)
+  var
+    formalParams = newNimNode(nnkFormalParams).add(b)
+    p = p
+    prag = newEmptyNode()
 
-  formalParams.add b
+  checkPragma(p, prag)
 
   case p.kind
   of nnkPar, nnkTupleConstr:
@@ -44,9 +53,7 @@ proc createProcType(p, b: NimNode): NimNode {.compileTime.} =
     formalParams.add identDefs
 
   result.add formalParams
-  result.add newEmptyNode()
-  #echo(treeRepr(result))
-  #echo(result.toStrLit())
+  result.add prag
 
 macro `=>`*(p, b: untyped): untyped =
   ## Syntax sugar for anonymous procedures.
@@ -58,56 +65,75 @@ macro `=>`*(p, b: untyped): untyped =
   ##
   ##   passTwoAndTwo((x, y) => x + y) # 4
 
-  #echo treeRepr(p)
-  #echo(treeRepr(b))
-  var params: seq[NimNode] = @[newIdentNode("auto")]
+  var
+    params = @[ident"auto"]
+    name = newEmptyNode()
+    kind = nnkLambda
+    pragma = newEmptyNode()
+    p = p
+
+  checkPragma(p, pragma)
+
+  if p.kind == nnkInfix and p[0].kind == nnkIdent and p[0].eqIdent"->":
+    params[0] = p[2]
+    p = p[1]
+
+  checkPragma(p, pragma) # check again after -> transform
+
+  since (1, 3):
+    if p.kind == nnkCall:
+      # foo(x, y) => x + y
+      kind = nnkProcDef
+      name = p[0]
+      let newP = newNimNode(nnkPar)
+      for i in 1..<p.len:
+        newP.add(p[i])
+      p = newP
 
   case p.kind
   of nnkPar, nnkTupleConstr:
-    for c in children(p):
+    var untypedBeforeColon = 0
+    for i, c in p:
       var identDefs = newNimNode(nnkIdentDefs)
       case c.kind
       of nnkExprColonExpr:
+        let t = c[1]
+        since (1, 3):
+          # + 1 here because of return type in params
+          for j in (i - untypedBeforeColon + 1) .. i:
+            params[j][1] = t
+        untypedBeforeColon = 0
         identDefs.add(c[0])
-        identDefs.add(c[1])
+        identDefs.add(t)
         identDefs.add(newEmptyNode())
       of nnkIdent:
         identDefs.add(c)
         identDefs.add(newIdentNode("auto"))
         identDefs.add(newEmptyNode())
+        inc untypedBeforeColon
       of nnkInfix:
-        if c[0].kind == nnkIdent and c[0].ident == !"->":
+        if c[0].kind == nnkIdent and c[0].eqIdent"->":
           var procTy = createProcType(c[1], c[2])
           params[0] = procTy[0][0]
           for i in 1 ..< procTy[0].len:
             params.add(procTy[0][i])
         else:
-          error("Expected proc type (->) got (" & $c[0].ident & ").")
+          error("Expected proc type (->) got (" & c[0].strVal & ").", c)
         break
       else:
-        echo treeRepr c
-        error("Incorrect procedure parameter list.")
+        error("Incorrect procedure parameter list.", c)
       params.add(identDefs)
   of nnkIdent:
     var identDefs = newNimNode(nnkIdentDefs)
     identDefs.add(p)
-    identDefs.add(newIdentNode("auto"))
+    identDefs.add(ident"auto")
     identDefs.add(newEmptyNode())
     params.add(identDefs)
-  of nnkInfix:
-    if p[0].kind == nnkIdent and p[0].ident == !"->":
-      var procTy = createProcType(p[1], p[2])
-      params[0] = procTy[0][0]
-      for i in 1 ..< procTy[0].len:
-        params.add(procTy[0][i])
-    else:
-      error("Expected proc type (->) got (" & $p[0].ident & ").")
   else:
-    error("Incorrect procedure parameter list.")
-  result = newProc(params = params, body = b, procType = nnkLambda)
-  #echo(result.treeRepr)
-  #echo(result.toStrLit())
-  #return result # TODO: Bug?
+    error("Incorrect procedure parameter list.", p)
+  result = newProc(body = b, params = params,
+                   pragmas = pragma, name = name,
+                   procType = kind)
 
 macro `->`*(p, b: untyped): untyped =
   ## Syntax sugar for procedure types.
@@ -190,7 +216,7 @@ macro capture*(locals: varargs[typed], body: untyped): untyped {.since: (1, 1).}
   result.add(newProc(newEmptyNode(), params, body, nnkProcDef))
   for arg in locals: result.add(arg)
 
-when (NimMajor, NimMinor) >= (1, 1):
+since (1, 1):
   import std / private / underscored_calls
 
   macro dup*[T](arg: T, calls: varargs[untyped]): T =

lib/pure/typetraits.nim

@@ -124,7 +124,7 @@ macro genericParamsImpl(T: typedesc): untyped =
           result.add ret
         break
       else:
-        error "wrong kind: " & $impl.kind
+        error "wrong kind: " & $impl.kind, impl
 
 since (1, 1):
   template genericParams*(T: typedesc): untyped =

tests/macros/tclosuremacro.nim

@@ -1,19 +1,16 @@
 discard """
-  output: '''10
-10
-10
-3
-3
+  output: '''
 noReturn
-6
 calling mystuff
 yes
 calling mystuff
 yes
+calling sugarWithPragma
+sugarWithPragma called
 '''
 """
 
-import future, macros
+import sugar, macros
 
 proc twoParams(x: (int, int) -> int): int =
   result = x(5, 5)
@@ -30,23 +27,23 @@ proc noReturn(x: () -> void) =
 proc doWithOneAndTwo(f: (int, int) -> int): int =
   f(1,2)
 
-echo twoParams(proc (a, b: auto): auto = a + b)
-echo twoParams((x, y) => x + y)
-
-echo oneParam(x => x+5)
-
-echo noParams(() => 3)
-
-echo doWithOneAndTwo((x, y) => x + y)
+doAssert twoParams(proc (a, b: auto): auto = a + b) == 10
+doAssert twoParams((x, y) => x + y) == 10
+doAssert oneParam(x => x+5) == 10
+doAssert noParams(() => 3) == 3
+doAssert doWithOneAndTwo((x, y) => x + y) == 3
 
 noReturn((() -> void) => echo("noReturn"))
 
 proc pass2(f: (int, int) -> int): (int) -> int =
   ((x: int) -> int) => f(2, x)
 
-echo pass2((x, y) => x + y)(4)
+doAssert pass2((x, y) => x + y)(4) == 6
 
+fun(x, y: int) {.noSideEffect.} => x + y
 
+doAssert typeof(fun) is (proc (x, y: int): int {.nimcall.})
+doAssert fun(3, 4) == 7
 
 proc register(name: string; x: proc()) =
   echo "calling ", name
@@ -72,3 +69,5 @@ macro m(x: untyped): untyped =
 m:
   proc mystuff() =
     echo "yes"
+
+sugarWithPragma() {.m.} => echo "sugarWithPragma called"