mutable decl syntax change

examples/programs/match/main.bro

@@ -63,18 +63,18 @@ make_box func() Box {
 }
 
 main func() i32 {
-	acc i32 = 0
+	acc i32 := 0
 
-	dog Data = Data{ dog = 9 }
-	bird Data = Data{ bird = 38 }
+	dog Data := Data{ dog = 9 }
+	bird Data := Data{ bird = 38 }
 	acc = acc + describe(dog) + describe(bird) # 10 + 40 = 50
 
 	# same-type multi-pattern capture
 	acc = acc + payload_of(dog) + payload_of(bird) # 9 + 38 = 47
 
 	# enum statement match, exhaustive, with a multi-pattern arm
-	a Animal = .bird
-	rank i32 = 0
+	a Animal := .bird
+	rank i32 := 0
 	match a {
 		.dog, .cat: rank = 1
 		.bird:      rank = 3
@@ -89,7 +89,7 @@ main func() i32 {
 	acc = acc + legs # +2
 
 	# scalar match: a range arm, a multi-literal arm, and a mandatory else
-	bucket i32 = 0
+	bucket i32 := 0
 	match rank {
 		0..3:  bucket = 1  # exclusive 0,1,2 — does not include 3
 		3, 4:  bucket = 5  # rank is 3
@@ -98,8 +98,8 @@ main func() i32 {
 	acc = acc + bucket # +5
 
 	# void-payload variant: contextual construction (`.empty` coerces to Box) + no-capture arm
-	e Box = .empty
-	hit i32 = 0
+	e Box := .empty
+	hit i32 := 0
 	match e {
 		.point |pt|: hit = pt.x
 		.empty:      hit = 7
@@ -107,7 +107,7 @@ main func() i32 {
 	acc = acc + hit # +7
 
 	# pointer capture mutates the subject's payload in place
-	b Box = Box{ point = Point{ x = 1, y = 2 } }
+	b Box := Box{ point = Point{ x = 1, y = 2 } }
 	match b {
 		.point |@p|: p.x = 10
 		.empty:      hit = hit