Make 'load' a keyword

RELNOTES[INC]:
  `load` is now a language keyword, it cannot be used as an identifier

PiperOrigin-RevId: 160944121

src/main/java/com/google/devtools/build/lib/syntax/Lexer.java

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java b/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
index e5805f5..61fdb60 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
@@ -528,6 +528,7 @@
     keywordMap.put("in", TokenKind.IN);
     keywordMap.put("is", TokenKind.IS);
     keywordMap.put("lambda", TokenKind.LAMBDA);
+    keywordMap.put("load", TokenKind.LOAD);
     keywordMap.put("nonlocal", TokenKind.NONLOCAL);
     keywordMap.put("not", TokenKind.NOT);
     keywordMap.put("or", TokenKind.OR);

src/main/java/com/google/devtools/build/lib/syntax/Parser.java

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Parser.java b/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
index f5e5b51..06f0ac9 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
@@ -1091,6 +1091,8 @@
   // load '(' STRING (COMMA [IDENTIFIER EQUALS] STRING)* COMMA? ')'
   private void parseLoad(List<Statement> list) {
     int start = token.left;
+    expect(TokenKind.LOAD);
+    expect(TokenKind.LPAREN);
     if (token.kind != TokenKind.STRING) {
       expect(TokenKind.STRING);
       return;
@@ -1165,21 +1167,12 @@
   }
 
   private void parseTopLevelStatement(List<Statement> list) {
-    // In Python grammar, there is no "top-level statement" and imports are
-    // considered as "small statements". We are a bit stricter than Python here.
-    // Check if there is an include
-    if (token.kind == TokenKind.IDENTIFIER) {
-      Token identToken = token;
-      Identifier ident = parseIdent();
-
-      if (ident.getName().equals("load") && token.kind == TokenKind.LPAREN) {
-        expect(TokenKind.LPAREN);
-        parseLoad(list);
-        return;
-      }
-      pushToken(identToken); // push the ident back to parse it as a statement
+    // Unlike Python imports, load statements can appear only at top-level.
+    if (token.kind == TokenKind.LOAD) {
+      parseLoad(list);
+    } else {
+      parseStatement(list, ParsingLevel.TOP_LEVEL);
     }
-    parseStatement(list, ParsingLevel.TOP_LEVEL);
   }
 
   // small_stmt | 'pass'

src/main/java/com/google/devtools/build/lib/syntax/TokenKind.java

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/TokenKind.java b/src/main/java/com/google/devtools/build/lib/syntax/TokenKind.java
index 52acce1..e5098f1 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/TokenKind.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/TokenKind.java
@@ -56,6 +56,7 @@
   LBRACKET("["),
   LESS("<"),
   LESS_EQUALS("<="),
+  LOAD("load"),
   LPAREN("("),
   MINUS("-"),
   MINUS_EQUALS("-="),

src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java

diff --git a/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java b/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
index 04eb664..62e176e 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/ParserTest.java
@@ -1236,7 +1236,7 @@
   public void testLoadNotAtTopLevel() throws Exception {
     setFailFast(false);
     parseFileForSkylark("if 1: load(8)\n");
-    assertContainsError("name 'load' is not defined");
+    assertContainsError("syntax error at 'load': expected expression");
   }
 
   @Test