runtime: fix map lookup does not set to default value if record is no…

…t exist (#129)

std/runtime/map.jule

@@ -186,13 +186,17 @@ impl _Map {
 	}
 
 	// Returns the |v| mapped by |k| if one exists.
-	// Sets |v| if found and pointer not nil.
+	// Sets |v| if pointer is not nil. If not found, sets to default value of Val.
 	// Same as the |ok| variable which reports whether |v| exist.
 	unsafe fn lookup(mut &self, mut k: Key, mut v: *Val, mut ok: *bool) {
 		if self == nil || self.groups == nil {
 			if ok != nil {
 				*ok = false
 			}
+			if v != nil {
+				let mut def: Val
+				*v = def
+			}
 			ret
 		}
 		hi, lo := splitHash(self.hash(k))
@@ -217,13 +221,18 @@ impl _Map {
 				if ok != nil {
 					*ok = false
 				}
+				if v != nil {
+					let mut def: Val
+					*v = def
+				}
 				ret
 			}
 			g += 1 // linear probing
 			if g >= u32(len(self.groups)) {
 				g = 0
 			}
 		}
+		panic("unreachable")
 	}
 
 	// Returns value of key if exist, otherwise returns default value of value type.
@@ -270,6 +279,7 @@ impl _Map {
 				g = 0
 			}
 		}
+		panic("unreachable")
 	}
 
 	// Attempts to remove |k|, returns true successful.
@@ -318,6 +328,7 @@ impl _Map {
 				g = 0
 			}
 		}
+		panic("unreachable")
 	}
 
 	// Removes all elements from the Map.