From 4e98dd9ce413e3b44ea94e897b97adad435a59c4 Mon Sep 17 00:00:00 2001
From: Renaud Pawlak <renaud.pawlak@gmail.com>
Date: Tue, 8 Nov 2016 14:58:58 +0100
Subject: [PATCH] improve error reporting when the scanner breaks

---
 .../org/jsweet/transpiler/JSweetProblem.java  | 13 +++++++--
 .../transpiler/util/AbstractTreeScanner.java  | 28 +++++++++++++++++++
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/src/main/java/org/jsweet/transpiler/JSweetProblem.java b/src/main/java/org/jsweet/transpiler/JSweetProblem.java
index 9364f49b..e1c4c1dd 100644
--- a/src/main/java/org/jsweet/transpiler/JSweetProblem.java
+++ b/src/main/java/org/jsweet/transpiler/JSweetProblem.java
@@ -34,6 +34,11 @@ public enum JSweetProblem {
 	 * Raised when the Java compiler reports an error.
 	 */
 	INTERNAL_JAVA_ERROR(Severity.ERROR),
+	/**
+	 * Raised when the transpiler meets an error while scanning the program's
+	 * AST.
+	 */
+	INTERNAL_TRANSPILER_ERROR(Severity.ERROR),
 	/**
 	 * Raised when the Tsc transpiler reports an error.
 	 */
@@ -266,10 +271,10 @@ public enum JSweetProblem {
 	 * Raised when a class tries to extend a Globals class.
 	 */
 	GLOBALS_CLASS_CANNOT_BE_SUBCLASSED(Severity.ERROR),
-    /**
+	/**
 	 * Raised when trying to access this from scope it isn't defined.
 	 */
-    CANNOT_ACCESS_THIS(Severity.ERROR),
+	CANNOT_ACCESS_THIS(Severity.ERROR),
 	/**
 	 * Raised when invoking a static method on this (this is allowed in Java,
 	 * but not in JSweet).
@@ -422,7 +427,7 @@ public enum JSweetProblem {
 			return String.format("globals classes cannot extend any class", params);
 		case GLOBALS_CLASS_CANNOT_BE_SUBCLASSED:
 			return String.format("globals classes cannot be subclassed", params);
-        case CANNOT_ACCESS_THIS:
+		case CANNOT_ACCESS_THIS:
 			return String.format("'this' isn't defined in scope of %s", params);
 		case CANNOT_ACCESS_STATIC_MEMBER_ON_THIS:
 			return String.format("member '%s' is static and cannot be accessed on 'this'", params);
@@ -432,6 +437,8 @@ public enum JSweetProblem {
 			return String.format("wrong key: method '$object' expects a list of key/value pairs as parameters, where keys are string literals", params);
 		case CYCLE_IN_STATIC_INITIALIZER_DEPENDENCIES:
 			return String.format("a cycle was detected in static intializers involving '%s'", params);
+		case INTERNAL_TRANSPILER_ERROR:
+			return String.format("internal transpiler error");
 		}
 		return null;
 	}
diff --git a/src/main/java/org/jsweet/transpiler/util/AbstractTreeScanner.java b/src/main/java/org/jsweet/transpiler/util/AbstractTreeScanner.java
index 738318a7..40400958 100644
--- a/src/main/java/org/jsweet/transpiler/util/AbstractTreeScanner.java
+++ b/src/main/java/org/jsweet/transpiler/util/AbstractTreeScanner.java
@@ -155,11 +155,39 @@ public abstract class AbstractTreeScanner extends TreeScanner {
 			} else {
 				throw rollback;
 			}
+		} catch (Exception e) {
+			report(tree, JSweetProblem.INTERNAL_TRANSPILER_ERROR);
+			dumpStackTrace();
 		} finally {
 			exit();
 		}
 	}
 
+	protected void dumpStackTrace() {
+		System.err.println("dumping transpiler's strack trace:");
+		for (int i = stack.size() - 1; i >= 0; i--) {
+			JCTree tree = stack.get(i);
+			if (tree == null) {
+				continue;
+			}
+			String str = tree.toString().trim();
+			int intialLength = str.length();
+			int index = str.indexOf('\n');
+			if (index > 0) {
+				str = str.substring(0, index + 1);
+			}
+			str = str.replace('\n', ' ');
+			str = str.substring(0, Math.min(str.length() - 1, 30));
+			System.err.print("   [" + stack.get(i).getClass().getSimpleName() + "] " + str + (str.length() < intialLength ? "..." : "") + " ("
+					+ compilationUnit.getSourceFile().getName() + ":");
+			if (diagnosticSource == null) {
+				System.err.println(tree.pos + ")");
+			} else {
+				System.err.println(diagnosticSource.getLineNumber(tree.pos) + ")");
+			}
+		}
+	}
+
 	protected void onRollbacked(JCTree target) {
 	}