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Fix overlapping match statements (thanks Mako)

	We were overly aggressive in unifying wildcards.

--- a/mi/match.c

+++ b/mi/match.c

@@ -16,6 +16,7 @@

 typedef struct Dtree Dtree;

 struct Dtree {

 	int id;

+	int obscured;

 	Srcloc loc;

 	/* values for matching */

@@ -361,14 +362,13 @@

 		for (i = 0; i < ty->nmemb; i++) {

 			uc = ty->udecls[i];

 			next = dtbytag(start, uc);

-			if (next) {

-				if (uc->etype) {

-					if (addwildrec(loc, uc->etype, next, accept, end, nend))

-						ret = 1;

-				} else {

-					lappend(end, nend, next);

-				}

-			}

+			if (!next)

+				continue;

+

+			if (uc->etype && addwildrec(loc, uc->etype, next, accept, end, nend))

+				ret = 1;

+			else

+				lappend(end, nend, next);

 		}

 		if (!start->any) {

 			start->any = accept;

@@ -408,10 +408,8 @@

 	Dtree *next;

 	Ucon *uc;

-	if (start->any) {

+	if (start->any)

 		lappend(end, nend, start->any);

-		return 0;

-	}

 	uc = finducon(tybase(exprtype(pat)), pat->expr.args[0]);

 	next = dtbytag(start, uc);

@@ -434,13 +432,15 @@

 	lappend(&start->pat, &start->npat, tagid);

 	if (uc->etype) {

 		next = mkdtree(pat->loc, genlbl(pat->loc));

+		next->obscured = (start->obscured || start->any != NULL);

 		lappend(&start->next, &start->nnext, next);

 		addpat(pat->expr.args[1], uvalue(val, uc->etype), next, accept, cap, ncap, end, nend);

 	} else {

+		accept->obscured = (start->obscured || start->any != NULL);

 		lappend(&start->next, &start->nnext, accept);

 		lappend(end, nend, accept);

 	}

-	return 1;

+	return !start->obscured && start->any == NULL;

 }

 static int

@@ -502,12 +502,10 @@

 	if (pat->expr.args[0]->lit.littype == Lstr) {

 		return addstr(pat, val, start, accept, cap, ncap, end, nend);

 	} else {

-		/* if we already have a match, we're not adding a new node */

-		if (start->any) {

+		if (start->any)

 			lappend(end, nend, start->any);

-			return 0;

-		}

+		/* if we already have a match, we're not adding a new node */

 		for (i = 0; i < start->npat; i++) {

 			if (liteq(start->pat[i]->expr.args[0], pat->expr.args[0])) {

 				lappend(end, nend, start->next[i]);

@@ -520,10 +518,11 @@

 			start->load = val;

 			start->nconstructors = nconstructors(exprtype(pat));

 		}

+		accept->obscured = (start->obscured || start->any != NULL);

 		lappend(&start->pat, &start->npat, pat);

 		lappend(&start->next, &start->nnext, accept);

 		lappend(end, nend, accept);

-		return 1;

+		return !start->obscured && start->any == NULL;

 	}

 }

--- /dev/null

+++ b/test/matchoverwild.myr

@@ -1,0 +1,43 @@

+use std

+

+type ast = struct

+	body : op[:]

+;;

+type op = union

+	`Go int

+	`Set int

+	`Add int

+	`Mul (int, int)

+	`Read

+	`Write

+	`Loop ast

+;;

+

+const combine = {lhs : op, rhs : op

+	match (lhs, rhs)

+	| (`Add x, `Add y): -> `std.Some `Add (x + y)

+	| (`Go x, `Go y): -> `std.Some `Go (x + y)

+	| (`Go 0, _): -> `std.Some rhs

+	| (`Set x, `Add y): -> `std.Some `Set(x + y)

+	| (`Add _, `Set y): -> `std.Some rhs

+	| (`Add _, `Read): -> `std.Some rhs

+	| (`Set _, `Read): -> `std.Some rhs

+	| (`Loop _, `Loop _): -> `std.Some lhs

+	| _: -> `std.None

+	;;

+}

+

+const main = {

+	match combine(`Add 123, `Set 246)

+	| `std.Some `Set 246:

+		/* ok */

+	| r:

+		std.fatal("bad combine {}\n", r)

+	;;

+	match combine(`Add 123, `Add 246)

+	| `std.Some `Add 369:

+		/* ok */

+	| r:

+		std.fatal("bad combine {}\n", r)

+	;;

+}

--- a/test/tests

+++ b/test/tests

@@ -110,6 +110,7 @@

 B gsizeof	E	5

 B matchint	E	84

 B matchconst	E	88

+B matchoverwild	E	0

 B matchnsconst	P	'matched badchar'

 B matchunion	E	84

 B matchtup	E	42

@@ -148,6 +149,7 @@

 B strjoin	C

 B exporttrait	E	0

 B local-labels	E	10

+B empty-struct	E	21

 B empty-struct	E	21

 F declmismatch

 F infermismatch