From cbd2f97c5b13d7b7dbe2e62823447a8cecec77ee Mon Sep 17 00:00:00 2001
From: Eric Swanson <eric.the.unicorn@gmail.com>
Date: Tue, 22 Sep 2020 03:11:25 -0700
Subject: [PATCH] Add an error message about known reserved words (#322)

---
 .../bscript/compiler/file/ErrorListener.cpp   | 22 ++++++++++++++++++-
 ...ors004-reserved-word-as-argument-name.err2 |  2 +-
 .../errors010-reserved-word-syntax-error.err1 |  1 +
 .../errors010-reserved-word-syntax-error.err2 |  1 +
 .../errors010-reserved-word-syntax-error.src  |  2 ++
 5 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 testsuite/escript/errors/errors010-reserved-word-syntax-error.err1
 create mode 100644 testsuite/escript/errors/errors010-reserved-word-syntax-error.err2
 create mode 100644 testsuite/escript/errors/errors010-reserved-word-syntax-error.src

diff --git a/pol-core/bscript/compiler/file/ErrorListener.cpp b/pol-core/bscript/compiler/file/ErrorListener.cpp
index dad21d5cb8..5188d807b9 100644
--- a/pol-core/bscript/compiler/file/ErrorListener.cpp
+++ b/pol-core/bscript/compiler/file/ErrorListener.cpp
@@ -1,10 +1,19 @@
 #include "ErrorListener.h"
 
+#include <set>
+
+#include "clib/maputil.h"
 #include "compiler/Profile.h"
 #include "compiler/Report.h"
 
 namespace Pol::Bscript::Compiler
 {
+std::set<std::string, Clib::ci_cmp_pred> easily_overlooked_reserved_words = {
+    "as", "byval", "double", "downto", "float", "hash",
+    "in", "integer", "is", "long", "out", "real",
+    "signed", "stack", "step", "string", "to", "unsigned"
+};
+
 ErrorListener::ErrorListener( std::string pathname, Profile& profile )
     : pathname( std::move( pathname ) ), profile( profile )
 {
@@ -19,10 +28,21 @@ void ErrorListener::propagate_errors_to( Report& report, const SourceFileIdentif
   }
 }
 
-void ErrorListener::syntaxError( antlr4::Recognizer*, antlr4::Token* /*offendingSymbol*/,
+void ErrorListener::syntaxError( antlr4::Recognizer*, antlr4::Token* offendingSymbol,
                                  size_t line, size_t charPositionInLine, const std::string& msg,
                                  std::exception_ptr )
 {
+  if ( offendingSymbol )
+  {
+    std::string symbol = offendingSymbol->getText();
+    if ( easily_overlooked_reserved_words.count( symbol ) )
+    {
+      fmt::Writer w;
+      w << "Did not expect reserved word '" << symbol << "' in this context.\n";
+      error_messages.push_back( { w.str(), line, charPositionInLine + 1 } );
+    }
+  }
+
   error_messages.push_back( { msg, line, charPositionInLine+1 } );
 }
 
diff --git a/testsuite/escript/errors/errors004-reserved-word-as-argument-name.err2 b/testsuite/escript/errors/errors004-reserved-word-as-argument-name.err2
index 1a537c3ae4..0d9ce7d6a9 100644
--- a/testsuite/escript/errors/errors004-reserved-word-as-argument-name.err2
+++ b/testsuite/escript/errors/errors004-reserved-word-as-argument-name.err2
@@ -1 +1 @@
-errors004-reserved-word-as-argument-name.src:3:13: error: extraneous input 'downto' expecting {'unused', ')', IDENTIFIER}
\ No newline at end of file
+errors004-reserved-word-as-argument-name.src:3:13: error: Did not expect reserved word 'downto' in this context.
\ No newline at end of file
diff --git a/testsuite/escript/errors/errors010-reserved-word-syntax-error.err1 b/testsuite/escript/errors/errors010-reserved-word-syntax-error.err1
new file mode 100644
index 0000000000..53cd797bed
--- /dev/null
+++ b/testsuite/escript/errors/errors010-reserved-word-syntax-error.err1
@@ -0,0 +1 @@
+Non-identifier declared as a variable: 'is'
\ No newline at end of file
diff --git a/testsuite/escript/errors/errors010-reserved-word-syntax-error.err2 b/testsuite/escript/errors/errors010-reserved-word-syntax-error.err2
new file mode 100644
index 0000000000..545831c97c
--- /dev/null
+++ b/testsuite/escript/errors/errors010-reserved-word-syntax-error.err2
@@ -0,0 +1 @@
+errors010-reserved-word-syntax-error.src:1:5: error: Did not expect reserved word 'is' in this context.
\ No newline at end of file
diff --git a/testsuite/escript/errors/errors010-reserved-word-syntax-error.src b/testsuite/escript/errors/errors010-reserved-word-syntax-error.src
new file mode 100644
index 0000000000..2d11630ded
--- /dev/null
+++ b/testsuite/escript/errors/errors010-reserved-word-syntax-error.src
@@ -0,0 +1,2 @@
+var is := 1;
+print("the value is " + is);