Fix: sourceCode#isSpaceBetweenTokens() checks non-adjacent tokens (#1…

…2491)

* Fix: sourceCode#isSpaceBetweenTokens() checks non-adjacent tokens

* Incorporate feedback :)

* Handle args in reverse order and when args overlap

* Extract helper function

lib/source-code/source-code.js

@@ -78,6 +78,18 @@ function sortedMerge(tokens, comments) {
     return result;
 }
 
+/**
+ * Determines if two nodes or tokens overlap.
+ * @param {ASTNode|Token} first The first node or token to check.
+ * @param {ASTNode|Token} second The second node or token to check.
+ * @returns {boolean} True if the two nodes or tokens overlap.
+ * @private
+ */
+function nodesOrTokensOverlap(first, second) {
+    return (first.range[0] <= second.range[0] && first.range[1] >= second.range[0]) ||
+        (second.range[0] <= first.range[0] && second.range[1] >= first.range[0]);
+}
+
 //------------------------------------------------------------------------------
 // Public Interface
 //------------------------------------------------------------------------------
@@ -411,19 +423,38 @@ class SourceCode extends TokenStore {
     }
 
     /**
-     * Determines if two tokens have at least one whitespace character
-     * between them. This completely disregards comments in making the
-     * determination, so comments count as zero-length substrings.
-     * @param {Token} first The token to check after.
-     * @param {Token} second The token to check before.
-     * @returns {boolean} True if there is only space between tokens, false
-     *  if there is anything other than whitespace between tokens.
+     * Determines if two nodes or tokens have at least one whitespace character
+     * between them. Order does not matter. Returns false if the given nodes or
+     * tokens overlap.
+     * @param {ASTNode|Token} first The first node or token to check between.
+     * @param {ASTNode|Token} second The second node or token to check between.
+     * @returns {boolean} True if there is a whitespace character between
+     * any of the tokens found between the two given nodes or tokens.
      * @public
      */
     isSpaceBetweenTokens(first, second) {
-        const text = this.text.slice(first.range[1], second.range[0]);
+        if (nodesOrTokensOverlap(first, second)) {
+            return false;
+        }
+
+        const [startingNodeOrToken, endingNodeOrToken] = first.range[1] <= second.range[0]
+            ? [first, second]
+            : [second, first];
+        const firstToken = this.getLastToken(startingNodeOrToken) || startingNodeOrToken;
+        const finalToken = this.getFirstToken(endingNodeOrToken) || endingNodeOrToken;
+        let currentToken = firstToken;
+
+        while (currentToken !== finalToken) {
+            const nextToken = this.getTokenAfter(currentToken, { includeComments: true });
+
+            if (currentToken.range[1] !== nextToken.range[0]) {
+                return true;
+            }
+
+            currentToken = nextToken;
+        }
 
-        return /\s/u.test(text.replace(/\/\*.*?\*\//gus, ""));
+        return false;
     }
 
     /**