fix: better error message for unused variable

The error message now reports the line where the variable was first
declared, rather than the end of the block in which id had to be
used.

compiler/symbols.go

@@ -1,16 +1,13 @@
 package compiler
 
 import (
-	"sort"
-	"strings"
-
 	"github.com/tucats/ego/errors"
 )
 
 type scope struct {
 	module string
 	depth  int
-	usage  map[string]bool
+	usage  map[string]*errors.Error
 }
 
 type scopeStack []scope
@@ -19,7 +16,7 @@ func newScope(name string, line int) scope {
 	return scope{
 		module: name,
 		depth:  line,
-		usage:  make(map[string]bool),
+		usage:  make(map[string]*errors.Error),
 	}
 }
 
@@ -43,25 +40,11 @@ func (c *Compiler) PopScope() error {
 		return nil
 	}
 
-	names := []string{}
-
 	scope := c.scopes[len(c.scopes)-1]
-	for name, used := range scope.usage {
-		if !used {
-			names = append(names, name)
-		}
-	}
-
-	if len(names) > 0 {
-		sort.Strings(names)
-
-		module := scope.module
-		if module != "" {
-			c.b.SetName(module)
-			module = ", at " + module
+	for _, used := range scope.usage {
+		if used != nil {
+			return used
 		}
-
-		return c.error(errors.ErrUnusedVariable, strings.Join(names, ", ")+module)
 	}
 
 	c.scopes = c.scopes[:len(c.scopes)-1]
@@ -74,7 +57,9 @@ func (c *Compiler) CreateVariable(name string) *Compiler {
 		c.PushScope()
 	}
 
-	c.scopes[len(c.scopes)-1].usage[name] = false
+	if _, found := c.scopes[len(c.scopes)-1].usage[name]; !found {
+		c.scopes[len(c.scopes)-1].usage[name] = c.error(errors.ErrUnusedVariable, name)
+	}
 
 	return c
 }
@@ -84,7 +69,7 @@ func (c *Compiler) UseVariable(name string) *Compiler {
 	// given variable. If found, mark it as used.
 	for i := len(c.scopes) - 1; i >= 0; i-- {
 		if _, found := c.scopes[i].usage[name]; found {
-			c.scopes[i].usage[name] = true
+			c.scopes[i].usage[name] = nil
 
 			break
 		}

tools/buildver.txt

@@ -1 +1 @@
-1.5-1176
+1.5-1177