Experimental standard library

Change import syntax and cover with tests

libsolidity/interface/CompilerStack.cpp

@@ -59,6 +59,8 @@
 #include <libsolidity/codegen/ir/Common.h>
 #include <libsolidity/codegen/ir/IRGenerator.h>
 
+#include <libstdlib/stdlib.h>
+
 #include <libyul/YulString.h>
 #include <libyul/AsmPrinter.h>
 #include <libyul/AsmJsonConverter.h>
@@ -95,6 +97,7 @@ using namespace std;
 using namespace solidity;
 using namespace solidity::langutil;
 using namespace solidity::frontend;
+using namespace solidity::stdlib;
 
 using solidity::util::errinfo_comment;
 
@@ -369,6 +372,15 @@ bool CompilerStack::parse()
 			for (auto const& import: ASTNode::filteredNodes<ImportDirective>(source.ast->nodes()))
 			{
 				solAssert(!import->path().empty(), "Import path cannot be empty.");
+				// Check whether the import directive is for the standard library,
+				// and if yes, add specified file to source units to be parsed.
+				auto it = stdlib::sources.find(import->path());
+				if (it != stdlib::sources.end())
+				{
+					auto [name, content] = *it;
+					m_sources[name].charStream = make_unique<CharStream>(content, name);
+					sourcesToParse.push_back(name);
+				}
 
 				// The current value of `path` is the absolute path as seen from this source file.
 				// We first have to apply remappings before we can store the actual absolute path

libsolidity/parsing/Parser.cpp

@@ -271,9 +271,9 @@ ASTPointer<ImportDirective> Parser::parseImportDirective()
 	SourceLocation unitAliasLocation{};
 	ImportDirective::SymbolAliasList symbolAliases;
 
-	if (m_scanner->currentToken() == Token::StringLiteral)
+	if (isQuotedPath() || isStdlibPath())
 	{
-		path = getLiteralAndAdvance();
+		path = isQuotedPath() ? getLiteralAndAdvance() : getStdlibImportPathAndAdvance();
 		if (m_scanner->currentToken() == Token::As)
 		{
 			advance();
@@ -315,9 +315,9 @@ ASTPointer<ImportDirective> Parser::parseImportDirective()
 		if (m_scanner->currentToken() != Token::Identifier || m_scanner->currentLiteral() != "from")
 			fatalParserError(8208_error, "Expected \"from\".");
 		advance();
-		if (m_scanner->currentToken() != Token::StringLiteral)
+		if (!isQuotedPath() && !isStdlibPath())
 			fatalParserError(6845_error, "Expected import path.");
-		path = getLiteralAndAdvance();
+		path = isQuotedPath() ? getLiteralAndAdvance() : getStdlibImportPathAndAdvance();
 	}
 	if (path->empty())
 		fatalParserError(6326_error, "Import path cannot be empty.");
@@ -2486,4 +2486,25 @@ ASTPointer<ASTString> Parser::getLiteralAndAdvance()
 	return identifier;
 }
 
+bool Parser::isQuotedPath() const
+{
+	return m_scanner->currentToken() == Token::StringLiteral;
+}
+
+bool Parser::isStdlibPath() const
+{
+	return m_experimentalSolidityEnabledInCurrentSourceUnit
+		&& m_scanner->currentToken() == Token::Identifier
+		&& m_scanner->currentLiteral() == "std";
+}
+
+ASTPointer<ASTString> Parser::getStdlibImportPathAndAdvance()
+{
+	ASTPointer<ASTString> std = expectIdentifierToken();
+	if (m_scanner->currentToken() == Token::Period)
+		advance();
+	ASTPointer<ASTString> library = expectIdentifierToken();
+	return make_shared<ASTString>(*std + "." + *library);
+}
+
 }

libsolidity/parsing/Parser.h

@@ -219,6 +219,11 @@ private:
 	ASTPointer<ASTString> getLiteralAndAdvance();
 	///@}
 
+	bool isQuotedPath() const;
+	bool isStdlibPath() const;
+
+	ASTPointer<ASTString> getStdlibImportPathAndAdvance();
+
 	/// Creates an empty ParameterList at the current location (used if parameters can be omitted).
 	ASTPointer<ParameterList> createEmptyParameterList();