bind generic param/or to constraint for conversion match

fixes nim-lang#4858, fixes nim-lang#10027, fixes nim-lang#12552, fixes nim-lang#15721, fixes nim-lang#21331, refs nim-lang#1214, follows up nim-lang#24216, split from nim-lang#24198

compiler/layeredtable.nim

@@ -80,3 +80,23 @@ proc put(typeMap: var LayeredIdTable, key: ItemId, value: PType) {.inline.} =
 template put*(typeMap: var LayeredIdTable, key, value: PType) =
   ## binds `key` to `value` only in current layer
   put(typeMap, key.itemId, value)
+
+proc putRecursive(typeMap: ref LayeredIdTableObj, key: ItemId, value: PType) =
+  var tm = typeMap
+  while tm != nil:
+    tm.topLayer[key] = value
+    tm = tm.nextLayer
+
+template putRecursive*(typeMap: ref LayeredIdTableObj, key, value: PType) =
+  ## binds `key` to `value` in all previous layers
+  putRecursive(typeMap, key.itemId, value)
+
+when not useRef:
+  proc putRecursive(typeMap: var LayeredIdTableObj, key: ItemId, value: PType) {.inline.} =
+    put(typeMap, key, value)
+    if typeMap.nextLayer != nil:
+      putRecursive(typeMap.nextLayer, key, value)
+
+  template putRecursive*(typeMap: var LayeredIdTableObj, key, value: PType) =
+    ## binds `key` to `value` in all previous layers
+    putRecursive(typeMap, key.itemId, value)

compiler/sigmatch.nim

@@ -1280,12 +1280,17 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
   if a.isResolvedUserTypeClass:
     return typeRel(c, f, a.skipModifier, flags)
 
-  template bindingRet(res) =
+  template bindingRet(res, bound) =
     if doBind:
-      let bound = aOrig.skipTypes({tyRange}).skipIntLit(c.c.idgen)
       put(c, f, bound)
     return res
 
+  template defaultBinding(): PType =
+    aOrig#[.skipTypes({tyRange})]#.skipIntLit(c.c.idgen)
+
+  template bindingRet(res) =
+    bindingRet(res, defaultBinding())
+
   template considerPreviousT(body: untyped) =
     var prev = lookup(c.bindings, f)
     if prev == nil: body
@@ -1831,18 +1836,42 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
       result = isNone
       let oldInheritancePenalty = c.inheritancePenalty
       var minInheritance = maxInheritancePenalty
+      var bestMatch: PType = nil
+        # the best match in the branches so far, preferring earlier branches
+        # this is to resolve ambiguity in cases like matching an int literal
+        # against `int8 | int16`, picking the earlier `int8`
+        # this keeps compatibility with legacy behavior
       for branch in f.kids:
         c.inheritancePenalty = -1
         let x = typeRel(c, branch, aOrig, flags)
         if x >= result:
           if  c.inheritancePenalty > -1:
-            minInheritance = min(minInheritance, c.inheritancePenalty)
+            if c.inheritancePenalty < minInheritance:
+              minInheritance = c.inheritancePenalty
+              if x > result:
+                # has to be strictly better so we prefer earlier matches
+                # also true for inheritance penalty in this case
+                bestMatch = branch
+          elif x > result:
+            # has to be strictly better so we prefer earlier matches
+            bestMatch = branch
           result = x
       if result >= isIntConv:
         if minInheritance < maxInheritancePenalty:
           c.inheritancePenalty = oldInheritancePenalty + minInheritance
+        var bound: PType = nil
+        if (result in {isConvertible, isIntConv, isSubrange, isFromIntLit} or
+            (result == isSubtype and a.isEmptyContainer)) and bestMatch != nil:
+          # match needs a conversion, bind to the constraint so the
+          # conversion can be generated
+          # supertypes act like typeclasses, only consider as concrete for
+          # empty collections
+          bound = bestMatch
+        else:
+          # default, bind to matched type
+          bound = defaultBinding()
         if result > isGeneric: result = isGeneric
-        bindingRet result
+        bindingRet result, bound
       else:
         result = isNone
   of tyNot:
@@ -1924,6 +1953,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
     let doBindGP = doBind or trBindGenericParam in flags
     var x = lookup(c.bindings, f)
     if x == nil:
+      var bound: PType = nil
       if c.callee.kind == tyGenericBody and not c.typedescMatched:
         # XXX: The fact that generic types currently use tyGenericParam for
         # their parameters is really a misnomer. tyGenericParam means "match
@@ -1957,11 +1987,35 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
       else:
         # check if 'T' has a constraint as in 'proc p[T: Constraint](x: T)'
         if f.len > 0 and f[0].kind != tyNone:
-          result = typeRel(c, f[0], a, flags + {trDontBind, trBindGenericParam})
+          # constraints need a new type binding context layer,
+          # so that matches to typeclasses in the constraint don't
+          # bind to that typeclass for the entire candidate
+          c.bindings = newTypeMapLayer(c.bindings)
+          # generic params in the constraint are an exception,
+          # so that we can infer things like `T: U`
+          result = typeRel(c, f[0], a, flags + {trBindGenericParam})
+          if f[0].skipTypes({tyAlias}).kind == tyOr:
+            # `or` types have special binding rules, they bind to
+            # one of their branches if the match needs a conversion
+            # we reuse this binding for the generic parameter
+            bound = lookup(c.bindings, f[0])
+            if bound == nil: bound = a
+          elif result in {isConvertible, isIntConv, isSubrange, isFromIntLit} or
+              (result == isSubtype and a.isEmptyContainer):
+            # match needs a conversion, bind to the constraint so the
+            # conversion can be generated
+            # supertypes act like typeclasses, only consider as concrete for
+            # empty collections
+            bound = f[0]
+          else:
+            # default, bind to matched type
+            bound = a
+          setToPreviousLayer(c.bindings)
           if doBindGP and result notin {isNone, isGeneric}:
-            let concrete = concreteType(c, a, f)
+            let concrete = concreteType(c, bound, f)
             if concrete == nil: return isNone
-            put(c, f, concrete)
+            # generic params have to be bound up to the root binding context
+            putRecursive(c.bindings, f, concrete)
           if result in {isEqual, isSubtype}:
             result = isGeneric
         elif a.kind == tyTypeDesc:
@@ -1973,7 +2027,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
           result = isGeneric
 
       if result == isGeneric:
-        var concrete = a
+        if bound == nil: bound = a
         if tfWildcard in a.flags:
           a.sym.transitionGenericParamToType()
           a.flags.excl tfWildcard
@@ -1983,11 +2037,12 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
           # reason about and maintain. Refactoring typeRel to not be responsible for setting, or
           # at least validating, bindings can have multiple benefits. This is debatable. I'm not 100% sure.
           # A design that allows a proper complexity analysis of types like `tyOr` would be ideal.
-          concrete = concreteType(c, a, f)
-          if concrete == nil:
+          bound = concreteType(c, bound, f)
+          if bound == nil:
             return isNone
         if doBindGP:
-          put(c, f, concrete)
+          # generic params have to be bound up to the root binding context
+          putRecursive(c.bindings, f, bound)
       elif result > isGeneric:
         result = isGeneric
     elif a.kind == tyEmpty:

lib/pure/os.nim

@@ -978,7 +978,7 @@ proc setLastModificationTime*(file: string, t: times.Time) {.noWeirdTarget.} =
   ## an error.
   when defined(posix):
     let unixt = posix.Time(t.toUnix)
-    let micro = convert(Nanoseconds, Microseconds, t.nanosecond)
+    let micro = convert(Nanoseconds, Microseconds, t.nanosecond).int32
     var timevals = [Timeval(tv_sec: unixt, tv_usec: micro),
       Timeval(tv_sec: unixt, tv_usec: micro)] # [last access, last modification]
     if utimes(file, timevals.addr) != 0: raiseOSError(osLastError(), file)

tests/overload/torconv.nim

@@ -0,0 +1,64 @@
+block:
+  proc foo(x: int16 | int32): string = $typeof(x)
+  proc bar[T: int16 | int32](x: T): string = $typeof(x)
+
+  doAssert foo(123) == "int16"
+  doAssert bar(123) == "int16"
+
+block: # issue #4858
+  type
+    SomeType = object
+      field1: uint
+
+  proc namedProc(an: var SomeType, b: SomeUnsignedInt) = discard
+
+  proc `+=`(an: var SomeType, b: SomeUnsignedInt) =
+    namedProc(an, b) # <---- error here
+
+  var t = SomeType()
+  namedProc(t, 0)
+  t += 0
+
+block: # issue #10027
+  type Uint24 = range[0'u32 .. 0xFFFFFF'u32]
+
+  proc a(v: SomeInteger|Uint24): string = $type(v)
+
+  doAssert a(42) == "int"
+  doAssert a(42.Uint24) == $Uint24
+
+block: # issue #12552
+  let x = 1'i8
+  proc foo(n : int): string = $typeof(n)
+  proc bar[T : int](n : T): string = $ typeof(n)
+  doAssert foo(x) == "int"
+  doAssert bar(x) == "int"
+
+block: # issue #15721
+  proc fn(a = 4, b: seq[string] or tuple[] = ()) =
+    discard # eg: when b is tuple[]: ...
+  fn(1)
+  fn(1, @[""])
+  var a: seq[string] = @[]
+  fn(1, a)
+  fn(1, seq[string](@[]))
+  fn(1, @[]) # BUG: error: conflicting types for 'fn__d58I39cH9a6bcpi3QDPJ5dBA'
+
+block: # issue #15721, set
+  proc fn(a = 4, b: set[uint8] or tuple[] = ()) =
+    discard # eg: when b is tuple[]: ...
+  fn(1)
+  fn(1, {1'u8})
+  var a: set[uint8] = {}
+  fn(1, a)
+  fn(1, set[uint8]({}))
+  fn(1, {}) # BUG: internal error: invalid kind for lastOrd(tyEmpty)
+
+block: # issue #21331
+  let a : int8 | uint8 = 3
+  doAssert sizeof(a)==sizeof(int8) # this fails
+
+block:
+  let x: range[0..5] = 1
+  proc foo[T: SomeInteger](x: T): string = $typeof(x)
+  discard foo(x)