Merge pull request microsoft#21426 from amcasey/AssertsForGH20809

amcasey · web-flow · commit ce7d998c4907 · 2018-01-31T10:49:30.000-08:00
Add asserts upstream from microsoft#20809
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
@@ -681,10 +681,21 @@ namespace ts {
             return getSpanOfTokenAtPosition(sourceFile, node.pos);
         }
 
-        const pos = nodeIsMissing(errorNode)
+        const isMissing = nodeIsMissing(errorNode);
+        const pos = isMissing
             ? errorNode.pos
             : skipTrivia(sourceFile.text, errorNode.pos);
 
+        // These asserts should all be satisfied for a properly constructed `errorNode`.
+        if (isMissing) {
+            Debug.assert(pos === errorNode.pos, "This failure could trigger https://github.com/Microsoft/TypeScript/issues/20809");
+            Debug.assert(pos === errorNode.end, "This failure could trigger https://github.com/Microsoft/TypeScript/issues/20809");
+        }
+        else {
+            Debug.assert(pos >= errorNode.pos, "This failure could trigger https://github.com/Microsoft/TypeScript/issues/20809");
+            Debug.assert(pos <= errorNode.end, "This failure could trigger https://github.com/Microsoft/TypeScript/issues/20809");
+        }
+
         return createTextSpanFromBounds(pos, errorNode.end);
     }
 
diff --git a/src/services/refactors/extractSymbol.ts b/src/services/refactors/extractSymbol.ts
@@ -335,6 +335,13 @@ namespace ts.refactor.extractSymbol {
                 Continue = 1 << 1,
                 Return = 1 << 2
             }
+
+            // We believe it's true because the node is from the (unmodified) tree.
+            Debug.assert(nodeToCheck.pos <= nodeToCheck.end, "This failure could trigger https://github.com/Microsoft/TypeScript/issues/20809");
+
+            // For understanding how skipTrivia functioned:
+            Debug.assert(!positionIsSynthesized(nodeToCheck.pos), "This failure could trigger https://github.com/Microsoft/TypeScript/issues/20809");
+
             if (!isStatement(nodeToCheck) && !(isExpressionNode(nodeToCheck) && isExtractableExpression(nodeToCheck))) {
                 return [createDiagnosticForNode(nodeToCheck, Messages.statementOrExpressionExpected)];
             }

Original file line number	Diff line number	Diff line change
`@@ -335,6 +335,13 @@ namespace ts.refactor.extractSymbol {`
`335`	`335`	`Continue = 1 << 1,`
`336`	`336`	`Return = 1 << 2`
`337`	`337`	`}`
	`338`	`+`
	`339`	`+ // We believe it's true because the node is from the (unmodified) tree.`
	`340`	`+ Debug.assert(nodeToCheck.pos <= nodeToCheck.end, "This failure could trigger https://github.com/Microsoft/TypeScript/issues/20809");`
	`341`	`+`
	`342`	`+ // For understanding how skipTrivia functioned:`
	`343`	`+ Debug.assert(!positionIsSynthesized(nodeToCheck.pos), "This failure could trigger https://github.com/Microsoft/TypeScript/issues/20809");`
	`344`	`+`
`338`	`345`	`if (!isStatement(nodeToCheck) && !(isExpressionNode(nodeToCheck) && isExtractableExpression(nodeToCheck))) {`
`339`	`346`	`return [createDiagnosticForNode(nodeToCheck, Messages.statementOrExpressionExpected)];`
`340`	`347`	`}`