Fix missing stack trace entry for assertions.

Fixes #467

Author: sbarzowski

internal/program/desugarer.go

@@ -339,9 +339,14 @@ func desugar(astPtr *ast.Node, objLevel int) (err error) {
 			node.Message = buildLiteralString("Assertion failed")
 		}
 		*astPtr = &ast.Conditional{
-			Cond:        node.Cond,
-			BranchTrue:  node.Rest,
-			BranchFalse: &ast.Error{Expr: node.Message},
+			Cond:       node.Cond,
+			BranchTrue: node.Rest,
+			BranchFalse: &ast.Error{
+				NodeBase: ast.NodeBase{
+					LocRange: *node.Loc(),
+				},
+				Expr: node.Message,
+			},
 		}
 		err = desugar(astPtr, objLevel)
 		if err != nil {

testdata/assert3.golden

@@ -1,6 +1,8 @@
 RUNTIME ERROR: Assertion failed
 -------------------------------------------------
-		
+	testdata/assert3:1:1-20	
+
+assert 42 != 42; 42
 
 -------------------------------------------------
 	During evaluation	

testdata/assert_failed.golden

@@ -1,6 +1,8 @@
 RUNTIME ERROR: Assertion failed
 -------------------------------------------------
-		
+	testdata/assert_failed:1:1-19	
+
+assert false; true
 
 -------------------------------------------------
 	During evaluation	

testdata/assert_failed_custom.golden

@@ -1,6 +1,8 @@
 RUNTIME ERROR: Custom Message
 -------------------------------------------------
-		
+	testdata/assert_failed_custom:1:1-38	
+
+assert false : "Custom Message"; true
 
 -------------------------------------------------
 	During evaluation