Implement the is operator for the new static and typedesc type classes

This also makes the first baby steps towards a sound treatment of
higher-order kinds (type type int).

Adds test cases showcasing the new features.

* Also fixes breakage after the rebase

tests/metatype/ttypedesc1.nim

@@ -5,15 +5,16 @@ type
     x: T
     y: U
 
-proc getTypeName(t: typedesc): string = t.name
+proc getTypeName1(t: typedesc): string = t.name
+proc getTypeName2(t: type): string = t.name
 
-proc foo(T: typedesc[float], a: auto): string =
+proc foo(T: type float, a: auto): string =
   result = "float " & $(a.len > 5)
 
 proc foo(T: typedesc[TFoo], a: int): string =
   result = "TFoo "  & $(a)
 
-proc foo(T: typedesc[int or bool]): string =
+proc foo(T: type[int or bool]): string =
   var a: T
   a = 10
   result = "int or bool " & ($a)
@@ -23,8 +24,8 @@ template foo(T: typedesc[seq]): string = "seq"
 test "types can be used as proc params":
   # XXX: `check` needs to know that TFoo[int, float] is a type and
   # cannot be assigned for a local variable for later inspection
-  check ((string.getTypeName == "string"))
-  check ((getTypeName(int) == "int"))
+  check ((string.getTypeName1 == "string"))
+  check ((getTypeName2(int) == "int"))
 
   check ((foo(TFoo[int, float], 1000) == "TFoo 1000"))
 
@@ -37,6 +38,25 @@ test "types can be used as proc params":
   check ((foo(seq[int]) == "seq"))
   check ((foo(seq[TFoo[bool, string]]) == "seq"))
 
-when false:
-  proc foo(T: typedesc[seq], s: T) = nil
+template accept(x) =
+  static: assert(compiles(x))
+
+template reject(x) =
+  static: assert(not compiles(x))
+
+var
+  si: seq[int]
+  ss: seq[string]
+
+proc foo(T: typedesc[seq], s: T) =
+  discard
+
+accept:
+  foo seq[int], si
+
+reject:
+  foo seq[string], si
+
+reject:
+  foo seq[int], ss
 

tests/metatype/ttypedesc3.nim

@@ -4,9 +4,9 @@ type
   Base = object of RootObj
   Child = object of Base
 
-proc pr(T: typedesc[Base]) = echo "proc " & T.name
-method me(T: typedesc[Base]) = echo "method " & T.name
-iterator it(T: typedesc[Base]): auto = yield "yield " & T.name
+proc pr(T: type[Base]) = echo "proc " & T.name
+method me(T: type[Base]) = echo "method " & T.name
+iterator it(T: type[Base]): auto = yield "yield " & T.name
 
 Base.pr
 Child.pr

tests/metatype/ttypeselectors.nim

@@ -5,16 +5,16 @@ output: "8\n8\n4"
 import
   macros, typetraits
 
-template selectType(x: int): typeDesc =
+template selectType(x: int): type =
   when x < 10:
     int
   else:
     string
 
-template simpleTypeTempl: typeDesc =
+template simpleTypeTempl: type =
   string
 
-macro typeFromMacro: typedesc = string
+macro typeFromMacro: type = string
 
 # The tests below check that the result variable of the
 # selected type matches the literal types in the code:

tests/parser/ttypeclasses.nim

@@ -1,17 +1,42 @@
-discard """
-    action: run
-"""
-
 type
     R = ref
     V = var
     D = distinct
     P = ptr
+    T = type
+    S = static
+    OBJ = object
+    TPL = tuple
+    SEQ = seq
 
+var i: int
 var x: ref int
 var y: distinct int
 var z: ptr int
+const C = @[1, 2, 3]
+
+static:
+  assert x is ref
+  assert y is distinct
+  assert z is ptr
+  assert C is static
+  assert C[1] is static[int]
+  assert C[0] is static[SomeInteger]
+  assert C isnot static[string]
+  assert C is SEQ|OBJ
+  assert C isnot OBJ|TPL
+  assert int is int
+  assert int is T
+  assert int is SomeInteger
+  assert seq[int] is type
+  assert seq[int] is type[seq]
+  assert seq[int] isnot type[seq[float]]
+  assert i isnot type[int]
+  assert type(i) is type[int]
+  assert x isnot T
+  assert y isnot S
+  assert z isnot enum
+  assert x isnot object
+  assert y isnot tuple
+  assert z isnot seq
 
-doAssert x is ref
-doAssert y is distinct
-doAssert z is ptr

tests/statictypes/tstatictypes.nim

@@ -1,25 +1,91 @@
 discard """
 nimout: '''
-staticAlialProc instantiated with 4
-staticAlialProc instantiated with 6
+staticAlialProc instantiated with 358
+staticAlialProc instantiated with 368
+'''
+output: '''
+16
+16
+b is 2 times a
+17
 '''
 """
 
 import macros
 
+template ok(x) = assert(x)
+template no(x) = assert(not x)
+
+template accept(x) =
+  static: assert(compiles(x))
+
+template reject(x) =
+  static: assert(not compiles(x))
+
 proc plus(a, b: int): int = a + b
 
+template isStatic(x: static): bool = true
+template isStatic(x: auto): bool = false
+
+var v = 1
+
 when true:
+  # test that `isStatic` works as expected
+  const C = 2
+
+  static:
+    ok C.isStatic
+    ok isStatic(plus(1, 2))
+    ok plus(C, 2).isStatic
+
+    no isStatic(v)
+    no plus(1, v).isStatic
+
+when true:
+  # test that proc instantiation works as expected
   type
     StaticTypeAlias = static[int]
 
-  proc staticAliasProc(s: StaticTypeAlias) =
-    static: echo "staticAlialProc instantiated with ", s + 1
-    echo s
+  proc staticAliasProc(a: StaticTypeAlias,
+                       b: static[int],
+                       c: static int) =
+    static:
+      assert a.isStatic and b.isStatic and c.isStatic
+      assert isStatic(a + plus(b, c))
+      echo "staticAlialProc instantiated with ", a, b, c
 
-  staticAliasProc 1+2
-  staticAliasProc 3
-  staticAliasProc 5
+    when b mod a == 0:
+      echo "b is ", b div a, " times a"
+
+    echo a + b + c
+
+  staticAliasProc 1+2, 5, 8
+  staticAliasProc 3, 2+3, 9-1
+  staticAliasProc 3, 3+3, 4+4
+
+when true:
+  # test static coercions. normal cases that should work:
+  accept:
+    var s1 = static[int] plus(1, 2)
+    var s2 = static(plus(1,2))
+    var s3 = static plus(1,2)
+    var s4 = static[SomeInteger](1 + 2)
+
+  # the sub-script operator can be used only with types:
+  reject:
+    var just_static3 = static[plus(1,2)]
+
+  # static coercion takes into account the type:
+  reject:
+    var x = static[string](plus(1, 2))
+  reject:
+    var x = static[string] plus(1, 2)
+  reject:
+    var x = static[SomeFloat] plus(3, 4)
+
+  # you cannot coerce a run-time variable
+  reject:
+    var x = static(v)
 
 when true:
   type
@@ -35,7 +101,7 @@ when true:
   var aw1: ArrayWrapper1[5]
   var aw2: ArrayWrapper2[5]
   var aw3: ArrayWrapper3[(10, "str")]
-  
+
   static:
     assert aw1.data.high == 5
     assert aw2.data.high == 6

tests/types/tisopr.nim

@@ -5,7 +5,7 @@ false
 false
 true
 true
-no'''
+yes'''
 """
 
 proc IsVoid[T](): string =