Fixed Skylark stack trace:

- Moved registration mechanism from BaseFunction into ASTNode / Statement / Expression
- Added more details about statements/expressions to the output trace (including if's)
- Fixed wrong locations

--
MOS_MIGRATED_REVID=102841164

1 files changed, 19 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Expression.java b/src/main/java/com/google/devtools/build/lib/syntax/Expression.java
index 1886843e86..f23746ad7e 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Expression.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Expression.java
@@ -36,8 +36,26 @@ public abstract class Expression extends ASTNode {
    * @return the result of evaluting the expression: a Java object corresponding
    *         to a datatype in the BUILD language.
    * @throws EvalException if the expression could not be evaluated.
+   * @throws InterruptedException may be thrown in a sub class.
    */
-  abstract Object eval(Environment env) throws EvalException, InterruptedException;
+  final Object eval(Environment env) throws EvalException, InterruptedException {
+    try {
+      return doEval(env);
+    } catch (EvalException | RuntimeException ex) {
+      throw handleException(ex);
+    }
+  }
+
+  /**
+   * Evaluates the expression and returns the result.
+   *
+   * <p>This method is only invoked by the super class {@link Expression} when calling {@link
+   * #eval(Environment)}.
+   *
+   * @throws EvalException if the expression could not be evaluated
+   * @throws InterruptedException may be thrown in a sub class.
+   */
+  abstract Object doEval(Environment env) throws EvalException, InterruptedException;
 
   /**
    * Returns the inferred type of the result of the Expression.