Fix import path grammar and grammar testing details.

Changelog.md

@@ -19,6 +19,7 @@ Compiler Features:
 
 
 Bugfixes:
+ * Antlr Grammar: Fix parsing of import paths involving properly distinguishing between empty and non-empty string literals in general.
  * AST Output: Fix ``kind`` field of ``ModifierInvocation`` for base constructor calls.
  * SMTChecker: Fix false positive and false negative on ``push`` as LHS of a compound assignment.
  * SMTChecker: Fix false positive in contracts that cannot be deployed.

docs/grammar.rst

@@ -2,12 +2,12 @@
 Language Grammar
 ****************
 
-.. a4:autogrammar:: Solidity
-   :only-reachable-from: Solidity.sourceUnit
+.. a4:autogrammar:: SolidityParser
+   :only-reachable-from: SolidityParser.sourceUnit
    :undocumented:
    :cc-to-dash:
 
 .. a4:autogrammar:: SolidityLexer
-   :only-reachable-from: Solidity.sourceUnit
+   :only-reachable-from: SolidityParser.sourceUnit
    :fragments:
    :cc-to-dash:

docs/grammar/SolidityLexer.g4

@@ -155,15 +155,20 @@ Not: '!';
 BitNot: '~';
 Inc: '++';
 Dec: '--';
+//@doc:inline
+DoubleQuote: '"';
+//@doc:inline
+SingleQuote: '\'';
 
 /**
- * A single quoted string literal restricted to printable characters.
- */
-StringLiteral: '"' DoubleQuotedStringCharacter* '"' | '\'' SingleQuotedStringCharacter* '\'';
-/**
- * A single non-empty quoted string literal.
+ * A non-empty quoted string literal restricted to printable characters.
  */
 NonEmptyStringLiteral: '"' DoubleQuotedStringCharacter+ '"' | '\'' SingleQuotedStringCharacter+ '\'';
+/**
+ * An empty string literal
+ */
+EmptyStringLiteral: '"' '"' | '\'' '\'';
+
 // Note that this will also be used for Yul string literals.
 //@doc:inline
 fragment DoubleQuotedStringCharacter: DoubleQuotedPrintable | EscapeSequence;
@@ -200,6 +205,7 @@ fragment DoubleQuotedUnicodeStringCharacter: ~["\r\n\\] | EscapeSequence;
 //@doc:inline
 fragment SingleQuotedUnicodeStringCharacter: ~['\r\n\\] | EscapeSequence;
 
+// Note that this will also be used for Yul hex string literals.
 /**
  * Hex strings need to consist of an even number of hex digits that may be grouped using underscores.
  */
@@ -315,6 +321,7 @@ YulDecimalNumber: '0' | ([1-9] [0-9]*);
 YulStringLiteral:
 	'"' DoubleQuotedStringCharacter* '"'
 	| '\'' SingleQuotedStringCharacter* '\'';
+//@doc:inline
 YulHexStringLiteral: HexString;
 
 YulWS: [ \t\r\n\u000C]+ -> skip ;

docs/grammar/SolidityParser.g4

@@ -1,7 +1,7 @@
 /**
  * Solidity is a statically typed, contract-oriented, high-level language for implementing smart contracts on the Ethereum platform.
  */
-grammar Solidity;
+parser grammar SolidityParser;
 
 options { tokenVocab=SolidityLexer; }
 
@@ -388,7 +388,7 @@ booleanLiteral: True | False;
 /**
  * A full string literal consists of either one or several consecutive quoted strings.
  */
-stringLiteral: StringLiteral+;
+stringLiteral: (NonEmptyStringLiteral | EmptyStringLiteral)+;
 /**
  * A full hex string literal that consists of either one or several consecutive hex strings.
  */

scripts/test_antlr_grammar.sh

@@ -39,19 +39,15 @@ prepare_workdir()
 prepare_workdir
 download_antlr4
 
-if [[ ! -f "${WORKDIR}/target/SolidityParser.class" ]] || \
-    [ "${GRAMMAR_FILE}" -nt "${WORKDIR}/target/SolidityParser.class" ]
-then
-  echo "Creating parser"
-  (
-  cd "${ROOT_DIR}"/docs/grammar
-  # Create lexer/parser from grammar
-  java -jar "${ANTLR_JAR}" Solidity.g4 SolidityLexer.g4 -o "${WORKDIR}/src/"
+echo "Creating parser"
+(
+cd "${ROOT_DIR}"/docs/grammar
+# Create lexer/parser from grammar
+java -jar "${ANTLR_JAR}" SolidityParser.g4 SolidityLexer.g4 -o "${WORKDIR}/src/"
 
-  # Compile lexer/parser sources
-  javac -classpath "${ANTLR_JAR}" "${WORKDIR}/src/"*.java -d "${WORKDIR}/target/"
-  )
-fi
+# Compile lexer/parser sources
+javac -classpath "${ANTLR_JAR}" "${WORKDIR}/src/"*.java -d "${WORKDIR}/target/"
+)
 
 # Run tests
 failed_count=0
@@ -67,11 +63,11 @@ test_file()
   local output
   if [[ "${solOrYul}" == "sol" ]]; then
     output=$(
-      java \
+      grep -v "^==== ExternalSource:" "${SOL_FILE}" | java \
         -classpath "${ANTLR_JAR}:${WORKDIR}/target/" \
         "org.antlr.v4.gui.TestRig" \
         Solidity \
-        sourceUnit <"${SOL_FILE}" 2>&1
+        sourceUnit 2>&1
     )
   else
     output=$(
@@ -113,7 +109,7 @@ while IFS='' read -r line
 do
   SOL_FILES+=("$line")
 done < <(
-  grep -riL -E \
+  grep --include "*.sol" -riL -E \
     "^\/\/ (Syntax|Type|Declaration)Error|^\/\/ ParserError (1684|2837|3716|3997|5333|6275|6281|6933|7319)|^==== Source:" \
     "${ROOT_DIR}/test/libsolidity/syntaxTests" \
     "${ROOT_DIR}/test/libsolidity/semanticTests" |