case var (#6608)

* [matcher] allow and encourage `case var <ident>` (see #6207)

* [std] add `case var` everywhere

* [matcher] give similarity warnings for plain idents

* fix tests

src/syntax/parser.mly

@@ -1551,6 +1551,10 @@ and parse_guard = parser
 	| [< '(Kwd If,p1); '(POpen,_); e = expr; '(PClose,_); >] ->
 		e
 
+and expr_or_var = parser
+	| [< '(Kwd Var,p1); name,p2 = dollar_ident; >] -> EVars [(name,p2),None,None],punion p1 p2
+	| [< e = expr >] -> e
+
 and parse_switch_cases eswitch cases = parser
 	| [< '(Kwd Default,p1); '(DblDot,_); s >] ->
 		let b,p2 = (try block_with_pos [] p1 s with Display e -> display (ESwitch (eswitch,cases,Some (Some e,punion p1 (pos e))),punion (pos eswitch) (pos e))) in
@@ -1561,7 +1565,7 @@ and parse_switch_cases eswitch cases = parser
 		let l , def = parse_switch_cases eswitch cases s in
 		(match def with None -> () | Some _ -> error Duplicate_default p1);
 		l , Some b
-	| [< '(Kwd Case,p1); el = psep Comma expr; eg = popt parse_guard; '(DblDot,_); s >] ->
+	| [< '(Kwd Case,p1); el = psep Comma expr_or_var; eg = popt parse_guard; '(DblDot,_); s >] ->
 		(match el with
 		| [] -> error (Custom "case without a pattern is not allowed") p1
 		| _ ->

src/typing/matcher.ml

@@ -160,7 +160,7 @@ module Pattern = struct
 			| TAbstract(a,_) -> unify ctx (TAbstract(a,[mk_mono()])) t p
 			| _ -> assert false
 
-	let rec make pctx t e =
+	let rec make pctx toplevel t e =
 		let ctx = pctx.ctx in
 		let p = pos e in
 		let fail () =
@@ -259,6 +259,22 @@ module Pattern = struct
 					if not (is_lower_ident s) && (match s.[0] with '`' | '_' -> false | _ -> true) then begin
 						display_error ctx "Capture variables must be lower-case" p;
 					end;
+					let sl = match follow t with
+						| TEnum(en,_) ->
+							en.e_names
+						| TAbstract({a_impl = Some c} as a,pl) when Meta.has Meta.Enum a.a_meta ->
+							ExtList.List.filter_map (fun cf ->
+								if Meta.has Meta.Impl cf.cf_meta && Meta.has Meta.Enum cf.cf_meta then Some cf.cf_name else None
+							) c.cl_ordered_statics
+						| _ ->
+							[]
+					in
+					begin match StringError.get_similar s sl with
+						| [] ->
+							if toplevel then
+								pctx.ctx.com.warning (Printf.sprintf "`case %s` has been deprecated, use `case var %s` instead" s s) p
+						| l -> pctx.ctx.com.warning ("Potential typo detected (expected similar values are " ^ (String.concat ", " l) ^ "). Consider using `var " ^ s ^ "` instead") p
+					end;
 					let v = add_local s p in
 					PatVariable v
 				end
@@ -313,7 +329,7 @@ module Pattern = struct
 								(* Allow using final _ to match "multiple" arguments *)
 								(PatAny,p) :: (match tl with [] -> [] | _ -> loop el tl)
 							| e :: el,(_,_,t) :: tl ->
-								make pctx t e :: loop el tl
+								make pctx false t e :: loop el tl
 							| [],(_,true,t) :: tl ->
 								(PatAny,pos e) :: loop [] tl
 							| [],[] ->
@@ -343,7 +359,7 @@ module Pattern = struct
 					| TFun(tl,tr) when tr == fake_tuple_type ->
 						let rec loop el tl = match el,tl with
 							| e :: el,(_,_,t) :: tl ->
-								let pat = make pctx t e in
+								let pat = make pctx false t e in
 								pat :: loop el tl
 							| [],[] -> []
 							| [],_ -> error "Not enough arguments" p
@@ -353,7 +369,7 @@ module Pattern = struct
 						PatTuple patterns
 					| TInst({cl_path=[],"Array"},[t2]) | (TDynamic _ as t2) ->
 						let patterns = ExtList.List.mapi (fun i e ->
-							make pctx t2 e
+							make pctx false t2 e
 						) el in
 						PatConstructor(ConArray (List.length patterns),patterns)
 					| _ ->
@@ -404,7 +420,7 @@ module Pattern = struct
 					try
 						if pctx.in_reification && cf.cf_name = "pos" then raise Not_found;
 						let e1 = Expr.field_assoc cf.cf_name fl in
-						make pctx t e1 :: patterns,cf.cf_name :: fields
+						make pctx false t e1 :: patterns,cf.cf_name :: fields
 					with Not_found ->
 						if is_matchable cf then
 							(PatAny,cf.cf_pos) :: patterns,cf.cf_name :: fields
@@ -415,9 +431,9 @@ module Pattern = struct
 				PatConstructor(ConFields fields,patterns)
 			| EBinop(OpOr,e1,e2) ->
 				let pctx1 = {pctx with current_locals = PMap.empty} in
-				let pat1 = make pctx1 t e1 in
+				let pat1 = make pctx1 toplevel t e1 in
 				let pctx2 = {pctx with current_locals = PMap.empty; or_locals = Some (pctx1.current_locals)} in
-				let pat2 = make pctx2 t e2 in
+				let pat2 = make pctx2 toplevel t e2 in
 				PMap.iter (fun name (v,p) ->
 					if not (PMap.mem name pctx2.current_locals) then verror name p;
 					pctx.current_locals <- PMap.add name (v,p) pctx.current_locals
@@ -428,13 +444,13 @@ module Pattern = struct
 					| (EConst (Ident s),p) ->
 						let v = add_local s p in
 						if in_display then ignore(Typer.display_expr ctx e (mk (TLocal v) v.v_type p) (WithType t) p);
-						let pat = make pctx t e2 in
+						let pat = make pctx false t e2 in
 						PatBind(v,pat)
 					| (EParenthesis e1,_) -> loop in_display e1
 					| (EDisplay(e1,_),_) -> loop true e1
 					| _ -> fail()
-					in
-					loop false e1
+				in
+				loop false e1
 			| EBinop(OpArrow,e1,e2) ->
 				let restore = save_locals ctx in
 				ctx.locals <- pctx.ctx_locals;
@@ -442,7 +458,7 @@ module Pattern = struct
 				let e1 = type_expr ctx e1 Value in
 				v.v_name <- "tmp";
 				restore();
-				let pat = make pctx e1.etype e2 in
+				let pat = make pctx toplevel e1.etype e2 in
 				PatExtractor(v,e1,pat)
 			| EDisplay(e,iscall) ->
 				let pat = loop e in
@@ -463,7 +479,7 @@ module Pattern = struct
 			or_locals = None;
 			in_reification = false;
 		} in
-		make pctx t e
+		make pctx true t e
 end
 
 module Case = struct

src/typing/type.ml

@@ -2848,11 +2848,16 @@ module StringError = struct
 		in
 		loop cl
 
-	let string_error_raise s sl msg =
-		if sl = [] then msg else
+	let get_similar s sl =
+		if sl = [] then [] else
 		let cl = List.map (fun s2 -> s2,levenshtein s s2) sl in
 		let cl = List.sort (fun (_,c1) (_,c2) -> compare c1 c2) cl in
 		let cl = filter_similar (fun s2 i -> i <= (min (String.length s) (String.length s2)) / 3) cl in
+		cl
+
+	let string_error_raise s sl msg =
+		if sl = [] then msg else
+		let cl = get_similar s sl in
 		match cl with
 			| [] -> raise Not_found
 			| [s] -> Printf.sprintf "%s (Suggestion: %s)" msg s

std/StringTools.hx

@@ -93,7 +93,7 @@ class StringTools {
 					ret.addChar(cast c1);
 					ret.addChar(cast c2);
 				}
-			case chr:
+			case var chr:
 				ret.addChar(cast chr);
 			}
 		}
@@ -548,7 +548,7 @@ class StringTools {
 						result.add(bs);
 						bs_buf = new StringBuf();
 						result.add('\\"');
-					case c:
+					case var c:
 						// Normal char
 						if (bs_buf.length > 0) {
 							result.add(bs_buf.toString());

std/cs/_std/sys/io/Process.hx

@@ -63,7 +63,7 @@ class Process {
 				case "Windows":
 					native.StartInfo.FileName = switch (Sys.getEnv("COMSPEC")) {
 						case null: "cmd.exe";
-						case comspec: comspec;
+						case var comspec: comspec;
 					}
 					native.StartInfo.Arguments = '/C "$cmd"';
 				case _:

std/haxe/io/Path.hx

@@ -235,7 +235,7 @@ class Path {
 					colon = true;
 				case "/".code if (!colon):
 					slashes = true;
-				case i:
+				case var i:
 					colon = false;
 					if (slashes) {
 						acc.add("/");

std/haxe/macro/TypeTools.hx

@@ -283,7 +283,7 @@ class TypeTools {
 			case TMono(tm):
 				switch(tm.get()) {
 					case null: t;
-					case t: f(t);
+					case var t: f(t);
 				}
 			case TEnum(_, []) | TInst(_, []) | TType(_, []):
 				t;

std/haxe/rtti/Rtti.hx

@@ -25,7 +25,7 @@ import haxe.rtti.CType;
 
 /**
 	Rtti is a helper class which supplements the `@:rtti` metadata.
-	
+
 	@see <https://haxe.org/manual/cr-rtti.html>
 **/
 class Rtti {
@@ -47,7 +47,7 @@ class Rtti {
 		var infos = new haxe.rtti.XmlParser().processElement(x);
 		switch (infos) {
 			case TClassdecl(c): return c;
-			case t: throw 'Enum mismatch: expected TClassDecl but found $t';
+			case var t: throw 'Enum mismatch: expected TClassDecl but found $t';
 		}
 	}
 

std/java/_std/sys/io/Process.hx

@@ -46,7 +46,7 @@ class Process {
 					pargs = new NativeArray(3);
 					pargs[0] = cmd = switch (Sys.getEnv("COMSPEC")) {
 						case null: "cmd.exe";
-						case comspec: comspec;
+						case var comspec: comspec;
 					}
 					pargs[1] = '/C';
 					pargs[2] = '"$cmdStr"';
@@ -102,7 +102,7 @@ class Process {
 				return null;
 			}
 		}
-		
+
 		cast(stdout, ProcessInput).bufferContents();
 		cast(stderr, ProcessInput).bufferContents();
 		try

std/java/internal/Exceptions.hx

@@ -73,13 +73,13 @@ class Exceptions {
 	{
 		return "Haxe Exception: " + obj;
 	}
-	
+
 	@:overload override public function getMessage():String
 	{
 		return switch (super.getMessage())
 		{
 			case null: Std.string(obj);
-			case message: message;
+			case var message: message;
 		}
 	}
 

std/php7/_std/StringTools.hx

@@ -166,7 +166,7 @@ import php.*;
 						result.add(bs);
 						bs_buf = new StringBuf();
 						result.add('\\"');
-					case c:
+					case var c:
 						// Normal char
 						if (bs_buf.length > 0) {
 							result.add(bs_buf.toString());

std/python/_std/Sys.hx

@@ -90,7 +90,7 @@ class Sys {
 
 	public static function systemName() : String {
 		return switch (python.lib.Sys.platform) {
-			case x if (StringTools.startsWith(x, "linux")):
+			case var x if (StringTools.startsWith(x, "linux")):
 				"Linux";
 			case "darwin": "Mac";
 			case "win32" | "cygwin" : "Windows";
@@ -142,7 +142,7 @@ class Sys {
 
 			case "Windows":
 				python.lib.Msvcrt.getch().decode("utf-8").charCodeAt(0);
-			case x :
+			case var x :
 				throw "platform " + x + " not supported";
 		}
 		if (echo) {

tests/misc/projects/Issue4907/compile-fail.hxml.stderr

@@ -1 +1,2 @@
-Main.hx:7: characters 18-23 : Capture variables must be lower-case
+Main.hx:7: characters 18-23 : Capture variables must be lower-case
+Main.hx:7: characters 18-23 : Warning : `case VALUE` has been deprecated, use `case var VALUE` instead

tests/misc/projects/Issue5268/Main.hx

@@ -6,7 +6,7 @@ class Main {
             case Some(v):
                 var value = switch v {
                     case 1: 1;
-                    case m: return None;
+                    case var m: return None;
                 }
                 value;
             case None:

tests/unit/src/unit/TestMatch.hx

@@ -82,7 +82,7 @@ class TestMatch extends Test {
 			case ["b"]: "2";
 			case [a]: "3:" + a;
 			case [a, b]: "4:" + a + "," +b;
-			case a if (a.length == 3): "5:" + a.length;
+			case var a if (a.length == 3): "5:" + a.length;
 			case []: "6";
 			case _: "7";
 		}
@@ -125,7 +125,7 @@ class TestMatch extends Test {
 		return switch(cl) {
 			case String: "String";
 			case MyClass: "unit.MyClass";
-			case a: "other: " +Type.getClassName(a);
+			case var a: "other: " +Type.getClassName(a);
 		}
 	}
 
@@ -231,7 +231,7 @@ class TestMatch extends Test {
 			case val = (4 | 5 | 6) if (val == 5): "1";
 			case 4, 5, 6: "2";
 			case 8, 9: "3";
-			case x: '_:$x';
+			case var x: '_:$x';
 		}
 		var results = ["_:0", "0", "0", "0", "2", "1", "2", "_:7", "3", "3", "_:10"];
 		for (i in 0...results.length) {
@@ -496,7 +496,7 @@ class TestMatch extends Test {
 			return switch(i) {
 				case [x]: 1;
 				case isPair(_) => Some(p) : p.a+p.b;
-				case arr: 3;
+				case var arr: 3;
 			}
 		}
 
@@ -552,7 +552,7 @@ class TestMatch extends Test {
 				case isPair(_) => Some({ a : is(even)(_) => Some(a), b : b }) : a+b;
 				case isPair(_) => Some({ a : isNot(even)(_) => Some(a), b : b }) : a*b;
 				case testArgs(1, "foo", _) => "[99,98,97]": 99;
-				case arr: 3;
+				case var arr: 3;
 			}
 		}
 

tests/unit/src/unit/issues/Issue2914.hx

@@ -6,18 +6,18 @@ class Issue2914 extends Test {
 
 		t(unit.HelperMacros.typeError({
 			var x = switch o {
-				case x if (x > 1): x;
+				case var x if (x > 1): x;
 			}
 		}));
 
 		var x = switch o {
-			case x if (x > 1): x;
-			case x: 1;
+			case var x if (x > 1): x;
+			case var x: 1;
 		}
 		eq(1, x);
 
 		switch (o) {
-			case y if (y < 1):
+			case var y if (y < 1):
 				x = 5;
 		}
 		eq(5, x);

tests/unit/src/unit/issues/Issue3031.hx

@@ -12,7 +12,7 @@ class Issue3031 extends Test {
 		var a = "";
 		switch (new StringBuf()) {
 			case null: a = "null";
-			case notNull: a = "not null";
+			case var notNull: a = "not null";
 		}
 		eq("not null", a);
 	}

tests/unit/src/unit/issues/Issue3150.hx

@@ -5,7 +5,7 @@ class Issue3150 extends Test {
 		t(unit.HelperMacros.typeError(
 			var d = switch (2) {
 				case 3: 90;
-				case f if (f == 0 | 2): -135;
+				case var f if (f == 0 | 2): -135;
 			}
 		));
 	}

tests/unit/src/unit/issues/Issue4677.hx

@@ -3,7 +3,7 @@ package unit.issues;
 class Issue4677 extends Test {
 	function test() {
 		var x = switch ("foo") {
-			case _1: _1;
+			case var _1: _1;
 		}
 		eq("foo", x);
 	}

tests/unit/src/unit/issues/Issue5392.hx

@@ -3,7 +3,7 @@ package unit.issues;
 private abstract A(Int) from Int {
     public function size() {
         return switch (this) {
-            case size: size;
+            case var size: size;
         }
     }
 }