add check for always true, and pretty warnings

cli/main.go

@@ -138,11 +138,15 @@ func makeChunk(ctx *Context, fpath string, ignoreWarnings bool) (*core.Chunk, er
 	}
 
 	// if there were non-critical warnings, report them
-	if !ignoreWarnings && len(c.Warnings) != 0 {
+	if len(c.Warnings) != 0 {
 		for _, warning := range c.Warnings {
-			log.Println(warning.Format())
+			log.Println(warning.Format() + "\n")
+		}
+		if !ignoreWarnings {
+			return nil, errors.New("compiler reported warning(s) (run anyways with --ignore-warnings)")
+		} else {
+			log.Println("compiler reported warning(s), but running anyways")
 		}
-		log.Fatal("compiler reported warning(s) (ignore warnings with the --ignore-warnings option)")
 	}
 
 	return c.Chunk, nil

core/compiler.go

@@ -279,6 +279,24 @@ func (c *Compiler) compile(tree Node) error {
 			return c.error(fmt.Sprintf("conditional requires boolean; cannot use non-boolean type %s", sig), n.condition)
 		}
 
+		if c.isTreeConstant(n.condition) {
+			v, err := c.compute(n.condition)
+			if err != nil {
+				return err
+			}
+
+			if v.(*BoolValue).Boolean {
+				c.warn("condition is always true", n.condition)
+				return c.compile(n.do)
+			} else {
+				c.warn("condition is always false", n.condition)
+				if n.otherwise != nil {
+					return c.compile(n.otherwise)
+				}
+				return nil
+			}
+		}
+
 		// the stack should have whether the condition was truthful
 		err = c.compile(n.condition)
 		if err != nil {
@@ -330,15 +348,34 @@ func (c *Compiler) compile(tree Node) error {
 			return c.error(fmt.Sprintf("cannot loop over value of type %s; requires boolean", sig), n.condition)
 		}
 
-		conditionPos := c.ip
-		err = c.compile(n.condition)
-		if err != nil {
-			return err
+		alwaysLoop := false
+		if c.isTreeConstant(n.condition) {
+			v, err := c.compute(n.condition)
+			if err != nil {
+				return err
+			}
+
+			if !v.(*BoolValue).Boolean {
+				c.warn("while-loop condition is always false", n.condition)
+				return nil
+			} else {
+				c.warn("while-loop condition is always true", n.condition)
+				alwaysLoop = true
+			}
 		}
 
-		c.add(InstructionJumpFalse)
-		jumpValuePos := c.ip
-		c.advance(2)
+		conditionPos := c.ip
+		jumpValuePos := Pos(0)
+		if !alwaysLoop {
+			err = c.compile(n.condition)
+			if err != nil {
+				return err
+			}
+
+			c.add(InstructionJumpFalse)
+			jumpValuePos = c.ip
+			c.advance(2)
+		}
 
 		err = c.compile(n.do)
 		if err != nil {
@@ -349,7 +386,9 @@ func (c *Compiler) compile(tree Node) error {
 		// condition pos < ip
 		c.addU16(uint16(c.ip - conditionPos + 2))
 
-		c.putU16(jumpValuePos, uint16(c.ip-jumpValuePos-2))
+		if !alwaysLoop {
+			c.putU16(jumpValuePos, uint16(c.ip-jumpValuePos-2))
+		}
 
 	case AssignNodeType:
 		n := tree.(*AssignNode)