top-down type inference, implements rfc 149 (nim-lang#20091)

* micro implementation of rfc 149

refs nim-lang/RFCs#149

* number/array/seq literals, more statements

* try fix number literal alias issue

* renew expectedType with if/case/try branch types

* fix (nerf) index type handling and float typed int

* use typeAllowed

* tweaks + const test (tested locally) [skip ci]

* fill out more of the checklist

* more literals, change @ order, type conversions

Not copying the full call tree before the typedesc call check
in `semIndirectOp` is also a small performance improvement.

* disable self-conversion warning

* revert type conversions (maybe separate op later)

* deal with CI for now (seems unrelated), try enums

* workaround CI different way

* proper fix

* again

* see sizes

* lol

* overload selection, simplify int literal -> float

* range, new @ solution, try use fitNode for nil

* use new magic

* try fix ranges, new magic, deal with nim-lang#20193

* add documentation, support templates

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

compiler/ast.nim

@@ -674,7 +674,7 @@ type
     mInSet, mRepr, mExit,
     mSetLengthStr, mSetLengthSeq,
     mIsPartOf, mAstToStr, mParallel,
-    mSwap, mIsNil, mArrToSeq,
+    mSwap, mIsNil, mArrToSeq, mOpenArrayToSeq,
     mNewString, mNewStringOfCap, mParseBiggestFloat,
     mMove, mWasMoved, mDestroy, mTrace,
     mDefault, mUnown, mFinished, mIsolate, mAccessEnv, mAccessTypeField, mReset,
@@ -708,8 +708,8 @@ type
     mSymIsInstantiationOf, mNodeId, mPrivateAccess
 
 
-# things that we can evaluate safely at compile time, even if not asked for it:
 const
+  # things that we can evaluate safely at compile time, even if not asked for it:
   ctfeWhitelist* = {mNone, mSucc,
     mPred, mInc, mDec, mOrd, mLengthOpenArray,
     mLengthStr, mLengthArray, mLengthSeq,
@@ -738,6 +738,9 @@ const
     mEqSet, mLeSet, mLtSet, mMulSet, mPlusSet, mMinusSet,
     mConStrStr, mAppendStrCh, mAppendStrStr, mAppendSeqElem,
     mInSet, mRepr}
+
+  generatedMagics* = {mNone, mIsolate, mFinished, mOpenArrayToSeq}
+    ## magics that are generated as normal procs in the backend
 
 type
   ItemId* = object
@@ -1677,6 +1680,10 @@ proc transitionIntKind*(n: PNode, kind: range[nkCharLit..nkUInt64Lit]) =
   transitionNodeKindCommon(kind)
   n.intVal = obj.intVal
 
+proc transitionIntToFloatKind*(n: PNode, kind: range[nkFloatLit..nkFloat128Lit]) =
+  transitionNodeKindCommon(kind)
+  n.floatVal = BiggestFloat(obj.intVal)
+
 proc transitionNoneToSym*(n: PNode) =
   transitionNodeKindCommon(nkSym)
 

compiler/ccgexprs.nim

@@ -2369,7 +2369,7 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
       genDollar(p, e, d, "#nimFloatToStr($1)")
   of mCStrToStr: genDollar(p, e, d, "#cstrToNimstr($1)")
   of mStrToStr, mUnown: expr(p, e[1], d)
-  of mIsolate, mFinished: genCall(p, e, d)
+  of generatedMagics: genCall(p, e, d)
   of mEnumToStr:
     if optTinyRtti in p.config.globalOptions:
       genEnumToStr(p, e, d)
@@ -2978,7 +2978,8 @@ proc expr(p: BProc, n: PNode, d: var TLoc) =
     if n[genericParamsPos].kind == nkEmpty:
       var prc = n[namePos].sym
       if useAliveDataFromDce in p.module.flags:
-        if p.module.alive.contains(prc.itemId.item) and prc.magic in {mNone, mIsolate, mFinished}:
+        if p.module.alive.contains(prc.itemId.item) and
+            prc.magic in generatedMagics:
           genProc(p.module, prc)
       elif prc.skipGenericOwner.kind == skModule and sfCompileTime notin prc.flags:
         if ({sfExportc, sfCompilerProc} * prc.flags == {sfExportc}) or

compiler/condsyms.nim

@@ -140,4 +140,5 @@ proc initDefines*(symbols: StringTableRef) =
   defineSymbol("nimHasEffectsOf")
 
   defineSymbol("nimHasEnforceNoRaises")
+  defineSymbol("nimHasTopDownInference")
   defineSymbol("nimHasTemplateRedefinitionPragma")

compiler/jsgen.nim

@@ -1455,7 +1455,7 @@ proc genSym(p: PProc, n: PNode, r: var TCompRes) =
           s.name.s)
     discard mangleName(p.module, s)
     r.res = s.loc.r
-    if lfNoDecl in s.loc.flags or s.magic notin {mNone, mIsolate} or
+    if lfNoDecl in s.loc.flags or s.magic notin generatedMagics or
        {sfImportc, sfInfixCall} * s.flags != {}:
       discard
     elif s.kind == skMethod and getBody(p.module.graph, s).kind == nkEmpty:
@@ -2106,6 +2106,8 @@ proc genMagic(p: PProc, n: PNode, r: var TCompRes) =
       gen(p, n[1], x)
       useMagic(p, "nimCopy")
       r.res = "nimCopy(null, $1, $2)" % [x.rdLoc, genTypeInfo(p, n.typ)]
+  of mOpenArrayToSeq:
+    genCall(p, n, r)
   of mDestroy, mTrace: discard "ignore calls to the default destructor"
   of mOrd: genOrd(p, n, r)
   of mLengthStr, mLengthSeq, mLengthOpenArray, mLengthArray:
@@ -2622,7 +2624,7 @@ proc gen(p: PProc, n: PNode, r: var TCompRes) =
     let s = n[namePos].sym
     discard mangleName(p.module, s)
     r.res = s.loc.r
-    if lfNoDecl in s.loc.flags or s.magic notin {mNone, mIsolate}: discard
+    if lfNoDecl in s.loc.flags or s.magic notin generatedMagics: discard
     elif not p.g.generatedSyms.containsOrIncl(s.id):
       p.locals.add(genProc(p, s))
   of nkType: r.res = genTypeInfo(p, n.typ)

compiler/sem.nim

@@ -27,11 +27,11 @@ when not defined(leanCompiler):
 
 # implementation
 
-proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode
-proc semExprWithType(c: PContext, n: PNode, flags: TExprFlags = {}): PNode
+proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}, expectedType: PType = nil): PNode
+proc semExprWithType(c: PContext, n: PNode, flags: TExprFlags = {}, expectedType: PType = nil): PNode
 proc semExprNoType(c: PContext, n: PNode): PNode
 proc semExprNoDeref(c: PContext, n: PNode, flags: TExprFlags = {}): PNode
-proc semProcBody(c: PContext, n: PNode): PNode
+proc semProcBody(c: PContext, n: PNode; expectedType: PType = nil): PNode
 
 proc fitNode(c: PContext, formal: PType, arg: PNode; info: TLineInfo): PNode
 proc changeType(c: PContext; n: PNode, newType: PType, check: bool)
@@ -48,7 +48,7 @@ proc semQuoteAst(c: PContext, n: PNode): PNode
 proc finishMethod(c: PContext, s: PSym)
 proc evalAtCompileTime(c: PContext, n: PNode): PNode
 proc indexTypesMatch(c: PContext, f, a: PType, arg: PNode): PNode
-proc semStaticExpr(c: PContext, n: PNode): PNode
+proc semStaticExpr(c: PContext, n: PNode; expectedType: PType = nil): PNode
 proc semStaticType(c: PContext, childNode: PNode, prev: PType): PType
 proc semTypeOf(c: PContext; n: PNode): PNode
 proc computeRequiresInit(c: PContext, t: PType): bool
@@ -269,12 +269,12 @@ proc paramsTypeCheck(c: PContext, typ: PType) {.inline.} =
   typeAllowedCheck(c, typ.n.info, typ, skProc)
 
 proc expectMacroOrTemplateCall(c: PContext, n: PNode): PSym
-proc semDirectOp(c: PContext, n: PNode, flags: TExprFlags): PNode
+proc semDirectOp(c: PContext, n: PNode, flags: TExprFlags; expectedType: PType = nil): PNode
 proc semWhen(c: PContext, n: PNode, semCheck: bool = true): PNode
 proc semTemplateExpr(c: PContext, n: PNode, s: PSym,
-                     flags: TExprFlags = {}): PNode
+                     flags: TExprFlags = {}; expectedType: PType = nil): PNode
 proc semMacroExpr(c: PContext, n, nOrig: PNode, sym: PSym,
-                  flags: TExprFlags = {}): PNode
+                  flags: TExprFlags = {}; expectedType: PType = nil): PNode
 
 proc symFromType(c: PContext; t: PType, info: TLineInfo): PSym =
   if t.sym != nil: return t.sym
@@ -334,8 +334,8 @@ proc fixupTypeAfterEval(c: PContext, evaluated, eOrig: PNode): PNode =
          isArrayConstr(arg):
         arg.typ = eOrig.typ
 
-proc tryConstExpr(c: PContext, n: PNode): PNode =
-  var e = semExprWithType(c, n)
+proc tryConstExpr(c: PContext, n: PNode; expectedType: PType = nil): PNode =
+  var e = semExprWithType(c, n, expectedType = expectedType)
   if e == nil: return
 
   result = getConstExpr(c.module, e, c.idgen, c.graph)
@@ -365,8 +365,8 @@ proc tryConstExpr(c: PContext, n: PNode): PNode =
 const
   errConstExprExpected = "constant expression expected"
 
-proc semConstExpr(c: PContext, n: PNode): PNode =
-  var e = semExprWithType(c, n)
+proc semConstExpr(c: PContext, n: PNode; expectedType: PType = nil): PNode =
+  var e = semExprWithType(c, n, expectedType = expectedType)
   if e == nil:
     localError(c.config, n.info, errConstExprExpected)
     return n
@@ -388,14 +388,14 @@ proc semConstExpr(c: PContext, n: PNode): PNode =
     else:
       result = fixupTypeAfterEval(c, result, e)
 
-proc semExprFlagDispatched(c: PContext, n: PNode, flags: TExprFlags): PNode =
+proc semExprFlagDispatched(c: PContext, n: PNode, flags: TExprFlags; expectedType: PType = nil): PNode =
   if efNeedStatic in flags:
     if efPreferNilResult in flags:
-      return tryConstExpr(c, n)
+      return tryConstExpr(c, n, expectedType)
     else:
-      return semConstExpr(c, n)
+      return semConstExpr(c, n, expectedType)
   else:
-    result = semExprWithType(c, n, flags)
+    result = semExprWithType(c, n, flags, expectedType)
     if efPreferStatic in flags:
       var evaluated = getConstExpr(c.module, result, c.idgen, c.graph)
       if evaluated != nil: return evaluated
@@ -414,7 +414,7 @@ proc resetSemFlag(n: PNode) =
       resetSemFlag(n[i])
 
 proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
-                       s: PSym, flags: TExprFlags): PNode =
+                       s: PSym, flags: TExprFlags; expectedType: PType = nil): PNode =
   ## Semantically check the output of a macro.
   ## This involves processes such as re-checking the macro output for type
   ## coherence, making sure that variables declared with 'let' aren't
@@ -438,10 +438,10 @@ proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
     case retType.kind
     of tyUntyped:
       # Not expecting a type here allows templates like in ``tmodulealias.in``.
-      result = semExpr(c, result, flags)
+      result = semExpr(c, result, flags, expectedType)
     of tyTyped:
       # More restrictive version.
-      result = semExprWithType(c, result, flags)
+      result = semExprWithType(c, result, flags, expectedType)
     of tyTypeDesc:
       if result.kind == nkStmtList: result.transitionSonsKind(nkStmtListType)
       var typ = semTypeNode(c, result, nil)
@@ -465,7 +465,7 @@ proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
         retType = generateTypeInstance(c, paramTypes,
                                        macroResult.info, retType)
 
-      result = semExpr(c, result, flags)
+      result = semExpr(c, result, flags, expectedType)
       result = fitNode(c, retType, result, result.info)
       #globalError(s.info, errInvalidParamKindX, typeToString(s.typ[0]))
   dec(c.config.evalTemplateCounter)
@@ -476,7 +476,7 @@ const
   errFloatToString = "cannot convert '$1' to '$2'"
 
 proc semMacroExpr(c: PContext, n, nOrig: PNode, sym: PSym,
-                  flags: TExprFlags = {}): PNode =
+                  flags: TExprFlags = {}; expectedType: PType = nil): PNode =
   rememberExpansion(c, nOrig.info, sym)
   pushInfoContext(c.config, nOrig.info, sym.detailedInfo)
 
@@ -496,7 +496,7 @@ proc semMacroExpr(c: PContext, n, nOrig: PNode, sym: PSym,
   #  c.evalContext = c.createEvalContext(emStatic)
   result = evalMacroCall(c.module, c.idgen, c.graph, c.templInstCounter, n, nOrig, sym)
   if efNoSemCheck notin flags:
-    result = semAfterMacroCall(c, n, result, sym, flags)
+    result = semAfterMacroCall(c, n, result, sym, flags, expectedType)
   if c.config.macrosToExpand.hasKey(sym.name.s):
     message(c.config, nOrig.info, hintExpandMacro, renderTree(result))
   result = wrapInComesFrom(nOrig.info, sym, result)
@@ -507,7 +507,7 @@ proc forceBool(c: PContext, n: PNode): PNode =
   if result == nil: result = n
 
 proc semConstBoolExpr(c: PContext, n: PNode): PNode =
-  result = forceBool(c, semConstExpr(c, n))
+  result = forceBool(c, semConstExpr(c, n, getSysType(c.graph, n.info, tyBool)))
   if result.kind != nkIntLit:
     localError(c.config, n.info, errConstExprExpected)
 

compiler/semdata.nim

@@ -120,10 +120,10 @@ type
     symMapping*: TIdTable      # every gensym'ed symbol needs to be mapped
                                # to some new symbol in a generic instantiation
     libs*: seq[PLib]           # all libs used by this module
-    semConstExpr*: proc (c: PContext, n: PNode): PNode {.nimcall.} # for the pragmas
-    semExpr*: proc (c: PContext, n: PNode, flags: TExprFlags = {}): PNode {.nimcall.}
+    semConstExpr*: proc (c: PContext, n: PNode; expectedType: PType = nil): PNode {.nimcall.} # for the pragmas
+    semExpr*: proc (c: PContext, n: PNode, flags: TExprFlags = {}, expectedType: PType = nil): PNode {.nimcall.}
     semTryExpr*: proc (c: PContext, n: PNode, flags: TExprFlags = {}): PNode {.nimcall.}
-    semTryConstExpr*: proc (c: PContext, n: PNode): PNode {.nimcall.}
+    semTryConstExpr*: proc (c: PContext, n: PNode; expectedType: PType = nil): PNode {.nimcall.}
     computeRequiresInit*: proc (c: PContext, t: PType): bool {.nimcall.}
     hasUnresolvedArgs*: proc (c: PContext, n: PNode): bool