macros: Introduce sameType(a, b) for node types

Previously introduced node comparison `==` was working somehow wrong on nodes
returned from getType(a), comparing just ids of the symbols.

Recently introduced `==` change 47dce26886
started comparing symbol nodes pointer-wise, thus strictly. Since getType(a)
always creates new symbol pointing to the type, comparing two such nodes using
`==` always returns false, even they point to the same type.

That is why we need a new sameType macro to be able to tell if these nodes
point to the same type.

compiler/ast.nim

@@ -587,7 +587,8 @@ type
     mNSetFloatVal, mNSetSymbol, mNSetIdent, mNSetType, mNSetStrVal, mNLineInfo,
     mNNewNimNode, mNCopyNimNode, mNCopyNimTree, mStrToIdent, mIdentToStr,
     mNBindSym, mLocals, mNCallSite,
-    mEqIdent, mEqNimrodNode, mNHint, mNWarning, mNError,
+    mEqIdent, mEqNimrodNode, mSameNodeType,
+    mNHint, mNWarning, mNError,
     mInstantiationInfo, mGetTypeInfo, mNGenSym
 
 # things that we can evaluate safely at compile time, even if not asked for it:

compiler/vm.nim

@@ -692,6 +692,9 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       regs[ra].intVal =
         ord(exprStructuralEquivalent(regs[rb].node, regs[rc].node,
                                      strictSymEquality=true))
+    of opcSameNodeType:
+      decodeBC(rkInt)
+      regs[ra].intVal = ord(regs[rb].node.typ.sameTypeOrNil regs[rc].node.typ)
     of opcXor:
       decodeBC(rkInt)
       regs[ra].intVal = ord(regs[rb].intVal != regs[rc].intVal)

compiler/vmdef.nim

@@ -60,8 +60,9 @@ type
     opcAddFloat, opcSubFloat, opcMulFloat, opcDivFloat, opcShrInt, opcShlInt,
     opcBitandInt, opcBitorInt, opcBitxorInt, opcAddu, opcSubu, opcMulu,
     opcDivu, opcModu, opcEqInt, opcLeInt, opcLtInt, opcEqFloat,
-    opcLeFloat, opcLtFloat, opcLeu, opcLtu, opcEqRef, opcEqNimrodNode, opcXor,
-    opcNot, opcUnaryMinusInt, opcUnaryMinusFloat, opcBitnotInt,
+    opcLeFloat, opcLtFloat, opcLeu, opcLtu,
+    opcEqRef, opcEqNimrodNode, opcSameNodeType,
+    opcXor, opcNot, opcUnaryMinusInt, opcUnaryMinusFloat, opcBitnotInt,
     opcEqStr, opcLeStr, opcLtStr, opcEqSet, opcLeSet, opcLtSet,
     opcMulSet, opcPlusSet, opcMinusSet, opcSymdiffSet, opcConcatStr,
     opcContainsSet, opcRepr, opcSetLenStr, opcSetLenSeq,

compiler/vmgen.nim

@@ -991,6 +991,7 @@ proc genMagic(c: PCtx; n: PNode; dest: var TDest; m: TMagic) =
   of mIdentToStr: genUnaryABC(c, n, dest, opcIdentToStr)
   of mEqIdent: genBinaryABC(c, n, dest, opcEqIdent)
   of mEqNimrodNode: genBinaryABC(c, n, dest, opcEqNimrodNode)
+  of mSameNodeType: genBinaryABC(c, n, dest, opcSameNodeType)
   of mNLineInfo: genUnaryABC(c, n, dest, opcNLineInfo)
   of mNHint:
     unused(n, dest)

lib/core/macros.nim

@@ -144,6 +144,10 @@ proc `==`*(a, b: NimIdent): bool {.magic: "EqIdent", noSideEffect.}
 proc `==`*(a, b: NimNode): bool {.magic: "EqNimrodNode", noSideEffect.}
   ## compares two Nim nodes
 
+proc sameType*(a, b: NimNode): bool {.magic: "SameNodeType", noSideEffect.}
+  ## compares two Nim nodes' types. Return true if the types are the same,
+  ## eg. true when comparing alias with original type.
+
 proc len*(n: NimNode): int {.magic: "NLen", noSideEffect.}
   ## returns the number of children of `n`.
 

tests/macros/tsametype.nim

@@ -0,0 +1,41 @@
+discard """
+output: '''1
+0
+1
+0
+1
+0
+1
+0
+1
+0'''
+"""
+
+import macros
+
+macro same(a: typedesc, b: typedesc): expr =
+  newLit(a.getType[1].sameType b.getType[1])
+
+echo same(int, int)
+echo same(int, float)
+
+type
+  SomeInt = int
+  DistinctInt = distinct int
+  SomeFloat = float
+  DistinctFloat = distinct float
+
+echo same(int, SomeInt)
+echo same(int, DistinctInt)
+echo same(float, SomeFloat)
+echo same(float, DistinctFloat)
+
+type
+  Obj = object of RootObj
+  SubObj = object of Obj
+  Other = object of RootObj
+
+echo same(Obj, Obj)
+echo same(int, Obj)
+echo same(SubObj, SubObj)
+echo same(Other, Obj)