fixes #1809; implements overloading based on 'var T'

compiler/parampatterns.nim

@@ -211,7 +211,7 @@ proc isAssignable*(owner: PSym, n: PNode): TAssignableResult =
     elif compareTypes(n.typ, n.sons[1].typ, dcEqIgnoreDistinct):
       # types that are equal modulo distinction preserve l-value:
       result = isAssignable(owner, n.sons[1])
-  of nkHiddenDeref, nkDerefExpr: 
+  of nkHiddenDeref, nkDerefExpr, nkHiddenAddr:
     result = arLValue
   of nkObjUpConv, nkObjDownConv, nkCheckedFieldExpr:
     result = isAssignable(owner, n.sons[0])
@@ -221,6 +221,9 @@ proc isAssignable*(owner: PSym, n: PNode): TAssignableResult =
   else:
     discard
 
+proc isLValue*(n: PNode): bool =
+  isAssignable(nil, n) in {arLValue, arLocalLValue}
+
 proc matchNodeKinds*(p, n: PNode): bool =
   # matches the parameter constraint 'p' against the concrete AST 'n'.
   # Efficiency matters here.

compiler/sigmatch.nim

@@ -191,21 +191,6 @@ proc complexDisambiguation(a, b: PType): int =
     for i in 1 .. <a.len: x += a.sons[i].sumGeneric
     for i in 1 .. <b.len: y += b.sons[i].sumGeneric
     result = x - y
-  when false:
-    proc betterThan(a, b: PType): bool {.inline.} = a.sumGeneric > b.sumGeneric
-
-    if a.len > 1 and b.len > 1:
-      let aa = a.sons[1].sumGeneric
-      let bb = b.sons[1].sumGeneric
-      var a = a
-      var b = b
-
-      if aa < bb: swap(a, b)
-      # all must be better
-      for i in 2 .. <min(a.len, b.len):
-        if not a.sons[i].betterThan(b.sons[i]): return 0
-      # a must be longer or of the same length as b:
-      result = a.len - b.len
 
 proc cmpCandidates*(a, b: TCandidate): int =
   result = a.exactMatches - b.exactMatches
@@ -1463,6 +1448,12 @@ proc matchesAux(c: PContext, n, nOrig: PNode,
       else:
         m.state = csNoMatch
         return
+    if formal.typ.kind == tyVar:
+      if n.isLValue:
+        inc(m.genericMatches, 100)
+      else:
+        m.state = csNoMatch
+        return
 
   var
     # iterates over formal parameters

todo.txt

@@ -3,7 +3,6 @@ version 0.10.4
 
 - improve GC-unsafety warnings
 - make 'nil' work for 'add' and 'len'
-- get rid of 'mget'; aka priority of 'var' needs to be 'var{lvalue}'
 - disallow negative indexing
 - improve the parser; deal with  echo $foo  gotcha
 
@@ -59,9 +58,9 @@ Bugs
 version 0.9.x
 =============
 
+- pragmas need 'bindSym' support
 - allow simple read accesses to global variables --> difficult to ensure that
   no data races happen
-- pragmas need 'bindSym' support
 - pragmas need re-work: 'push' is dangerous, 'hasPragma' does not work
   reliably with user-defined pragmas
 - memory manager: add a measure of fragmentation
@@ -76,7 +75,6 @@ version 0.9.X
 =============
 
 - macros as type pragmas
-- document how lazy overloading resolution works
 - document NimMain and check whether it works for threading
 
 GC

web/news.txt

@@ -4,7 +4,7 @@ News
 
 ..
   2015-03-01 Version 0.10.4 released
-  =================================
+  ==================================
 
 
   Changes affecting backwards compatibility
@@ -54,6 +54,17 @@ News
     takesBlock 1, 2, "some", 0.90, "random stuff":
       echo "yay"
 
+  - Overloading by 'var T' is now finally possible:
+
+  .. code-block:: nim
+    proc varOrConst(x: var int) = echo "var"
+    proc varOrConst(x: int) = echo "const"
+
+    var x: int
+    varOrConst(x) # "var"
+    varOrConst(45) # "const"
+
+
   Library additions
   -----------------
 
@@ -61,8 +72,8 @@ News
   - Added multipart param to httpclient's ``post`` and ``postContent`` together
     with a ``newMultipartData`` proc.
   - Added `%*` operator for JSON.
-  - The compiler is now a Nimble package.
-  - 
+  - The compiler is now available as Nimble package for c2nim.
+
 
   Bugfixes
   --------
@@ -103,8 +114,7 @@ News
     (`#1866 <https://github.com/Araq/Nim/issues/1866>`_).
   - Fixed "Incorrect assembler generated"
     (`#1907 <https://github.com/Araq/Nim/issues/1907>`_)
-  - Fixed "Expression templates that define macros are unusable in some contexts
-"
+  - Fixed "Expression templates that define macros are unusable in some contexts"
     (`#1903 <https://github.com/Araq/Nim/issues/1903>`_)
   - Fixed "a second level generic subclass causes the compiler to crash"
     (`#1919 <https://github.com/Araq/Nim/issues/1919>`_)
@@ -116,8 +126,7 @@ News
     (`#1838 <https://github.com/Araq/Nim/issues/1838>`_)
   - Fixed "ICE with template"
     (`#1915 <https://github.com/Araq/Nim/issues/1915>`_)
-  - Fixed "include the tool directory in the installer as it is required by koch
- "
+  - Fixed "include the tool directory in the installer as it is required by koch"
     (`#1947 <https://github.com/Araq/Nim/issues/1947>`_)
   - Fixed "Can't compile if file location contains spaces on Windows"
     (`#1955 <https://github.com/Araq/Nim/issues/1955>`_)
@@ -151,14 +160,11 @@ News
     (`#2039 <https://github.com/Araq/Nim/issues/2039>`_)
   - Fixed "Macros fail to compile when compiled with --os:standalone"
     (`#2041 <https://github.com/Araq/Nim/issues/2041>`_)
-  - Fixed "Reading from {.compileTime.} variables can cause code generation to f
-ail"
+  - Fixed "Reading from {.compileTime.} variables can cause code generation to fail"
     (`#2022 <https://github.com/Araq/Nim/issues/2022>`_)
-  - Fixed "Passing overloaded symbols to templates fails inside generic procedur
-es"
+  - Fixed "Passing overloaded symbols to templates fails inside generic procedures"
     (`#1988 <https://github.com/Araq/Nim/issues/1988>`_)
-  - Fixed "Compiling iterator with object assignment in release mode causes "var
- not init""
+  - Fixed "Compiling iterator with object assignment in release mode causes "var not init""
     (`#2023 <https://github.com/Araq/Nim/issues/2023>`_)
   - Fixed "calling a large number of macros doing some computation fails"
     (`#1989 <https://github.com/Araq/Nim/issues/1989>`_)
@@ -196,8 +202,7 @@ es"
     (`#2102 <https://github.com/Araq/Nim/issues/2102>`_)
   - Fixed "hint[path] = off not working in nim.cfg"
     (`#2103 <https://github.com/Araq/Nim/issues/2103>`_)
-  - Fixed "compiler crashes when getting a tuple from a sequence of generic tupl
-es"
+  - Fixed "compiler crashes when getting a tuple from a sequence of generic tuples"
     (`#2121 <https://github.com/Araq/Nim/issues/2121>`_)
   - Fixed "nim check hangs with when"
     (`#2123 <https://github.com/Araq/Nim/issues/2123>`_)
@@ -225,13 +230,11 @@ es"
     (`#2216 <https://github.com/Araq/Nim/issues/2216>`_)
   - Fixed "--threads:on breaks async"
     (`#2074 <https://github.com/Araq/Nim/issues/2074>`_)
-  - Fixed "Type mismatch not always caught, can generate bad code for C backend.
-"
+  - Fixed "Type mismatch not always caught, can generate bad code for C backend."
     (`#2169 <https://github.com/Araq/Nim/issues/2169>`_)
   - Fixed "Failed C compilation when storing proc to own type in object"
     (`#2233 <https://github.com/Araq/Nim/issues/2233>`_)
-  - Fixed "Unknown line/column number in constant declaration type conversion er
-ror"
+  - Fixed "Unknown line/column number in constant declaration type conversion error"
     (`#2252 <https://github.com/Araq/Nim/issues/2252>`_)
   - Fixed "Adding {.compile.} fails if nimcache already exists."
     (`#2247 <https://github.com/Araq/Nim/issues/2247>`_)