Phase 8.4: const func syntax — compile-time function declarations

src/ast.nim

@@ -323,6 +323,7 @@ type
     of dkFunc:
       declFuncAsm*: bool
       declFuncCallConv*: CallingConvention
+      declFuncConst*: bool          ## const func — evaluable at compile time
       declFuncName*: string
       declFuncTypeParams*: seq[string]
       declFuncParams*: seq[Param]

src/parser.nim

@@ -889,7 +889,7 @@ proc parseParamList(p: var Parser, allowVariadic: bool = false): seq[Param] =
       discard p.advance()
   discard p.expect(tkRParen, "expected ')' to close parameter list")
 
-proc parseFuncDecl(p: var Parser, isPublic: bool, isAsm: bool, attrs: ParsedAttrs): Decl =
+proc parseFuncDecl(p: var Parser, isPublic: bool, isAsm: bool, attrs: ParsedAttrs, isConst: bool = false): Decl =
   let loc = p.currentLoc
   discard p.expect(tkFunc, "expected 'func'")
   let name = p.expect(tkIdent, "expected function name").text
@@ -909,6 +909,7 @@ proc parseFuncDecl(p: var Parser, isPublic: bool, isAsm: bool, attrs: ParsedAttr
   return Decl(kind: dkFunc, loc: loc, isPublic: isPublic,
               declAttrs: declAttrs,
               declFuncAsm: isAsm, declFuncCallConv: attrs.callConv,
+              declFuncConst: isConst,
               declFuncName: name, declFuncTypeParams: typeParams,
               declFuncParams: params, declFuncReturnType: retType,
               declFuncBody: body)
@@ -1186,9 +1187,14 @@ proc parseDecl(p: var Parser): Decl =
   if p.check(tkAt):
     attrs = p.parseAttrs()
   
+  var isConst = false
+  if p.check(tkConst) and p.peek(1) == tkFunc:
+    isConst = true
+    discard p.advance()
+  
   case p.peek()
   of tkFunc:
-    return p.parseFuncDecl(isPublic, false, attrs)
+    return p.parseFuncDecl(isPublic, false, attrs, isConst)
   of tkStruct:
     return p.parseStructDecl(isPublic)
   of tkEnum: