Support referencing other constants in inline assembly

Changelog.md

@@ -3,6 +3,7 @@
 Language Features:
  * Allow to obtain the selector of public or external library functions via a member ``.selector``.
  * Parser: Allow splitting string and hexadecimal string literals into multiple parts.
+ * Inline Assembly: Support referencing other constants.
 
 
 Compiler Features:

libsolidity/CMakeLists.txt

@@ -41,6 +41,8 @@ set(sources
 	ast/ASTJsonConverter.h
 	ast/ASTPrinter.cpp
 	ast/ASTPrinter.h
+	ast/ASTUtils.cpp
+	ast/ASTUtils.h
 	ast/ASTVisitor.h
 	ast/ExperimentalFeatures.h
 	ast/Types.cpp

libsolidity/analysis/TypeChecker.cpp

@@ -22,6 +22,7 @@
 
 #include <libsolidity/analysis/TypeChecker.h>
 #include <libsolidity/ast/AST.h>
+#include <libsolidity/ast/ASTUtils.h>
 #include <libsolidity/ast/TypeProvider.h>
 
 #include <libyul/AsmAnalysis.h>
@@ -641,6 +642,8 @@ bool TypeChecker::visit(InlineAssembly const& _inlineAssembly)
 			solAssert(var->type(), "Expected variable type!");
 			if (var->isConstant())
 			{
+				var = rootVariableDeclaration(*var);
+
 				if (!var->value())
 				{
 					m_errorReporter.typeError(_identifier.location, "Constant has no value.");
@@ -651,7 +654,7 @@ bool TypeChecker::visit(InlineAssembly const& _inlineAssembly)
 					type(*var->value())->category() != Type::Category::RationalNumber
 				))
 				{
-					m_errorReporter.typeError(_identifier.location, "Only direct number constants are supported by inline assembly.");
+					m_errorReporter.typeError(_identifier.location, "Only direct number constants and references to such constants are supported by inline assembly.");
 					return size_t(-1);
 				}
 				else if (_context == yul::IdentifierContext::LValue)

libsolidity/ast/ASTUtils.cpp

@@ -0,0 +1,42 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <libsolidity/ast/AST.h>
+#include <libsolidity/ast/ASTUtils.h>
+
+namespace dev
+{
+namespace solidity
+{
+
+VariableDeclaration const* rootVariableDeclaration(VariableDeclaration const& _varDecl)
+{
+	solAssert(_varDecl.isConstant(), "Constant variable expected");
+
+	VariableDeclaration const* rootDecl = &_varDecl;
+	Identifier const* identifier;
+	while ((identifier = dynamic_cast<Identifier const*>(rootDecl->value().get())))
+	{
+		auto referencedVarDecl = dynamic_cast<VariableDeclaration const*>(identifier->annotation().referencedDeclaration);
+		solAssert(referencedVarDecl && referencedVarDecl->isConstant(), "Identifier is not referencing a variable declaration");
+		rootDecl = referencedVarDecl;
+	}
+	return rootDecl;
+}
+
+}
+}

libsolidity/ast/ASTUtils.h

@@ -0,0 +1,30 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+namespace dev
+{
+namespace solidity
+{
+
+/// Find the topmost referenced variable declaration when the given variable
+/// declaration value is an identifier. Works only for constant variable declarations.
+VariableDeclaration const* rootVariableDeclaration(VariableDeclaration const& _varDecl);
+
+}
+}

libsolidity/codegen/ContractCompiler.cpp

@@ -21,6 +21,7 @@
  */
 
 #include <libsolidity/ast/AST.h>
+#include <libsolidity/ast/ASTUtils.h>
 #include <libsolidity/ast/TypeProvider.h>
 #include <libsolidity/codegen/CompilerUtils.h>
 #include <libsolidity/codegen/ContractCompiler.h>
@@ -631,6 +632,7 @@ bool ContractCompiler::visit(InlineAssembly const& _inlineAssembly)
 			{
 				if (variable->isConstant())
 				{
+					variable = rootVariableDeclaration(*variable);
 					u256 value;
 					if (variable->value()->annotation().type->category() == Type::Category::RationalNumber)
 					{

test/libsolidity/semanticTests/inlineAssembly/constant_access_referencing.sol

@@ -0,0 +1,26 @@
+contract C {
+    uint constant a = 2;
+    uint constant aa = a;
+    uint constant aaa = aa;
+    bytes2 constant b = 0xabcd;
+    bytes2 constant bb = b;
+    bytes3 constant c = "abc";
+    bytes3 constant cc = c;
+    bytes3 constant ccc = cc;
+    bytes3 constant cccc = ccc;
+    bool constant d = true;
+    bool constant dd = d;
+    address payable constant e = 0x1212121212121212121212121212121212121212;
+    address payable constant ee = e;
+    function f() public pure returns (uint w, bytes2 x, bytes3 y, bool z, address t) {
+        assembly {
+            w := aaa
+            x := bb
+            y := cccc
+            z := dd
+            t := ee
+        }
+    }
+}
+// ----
+// f() -> 2, left(0xabcd), left(0x616263), true, 0x1212121212121212121212121212121212121212

test/libsolidity/syntaxTests/inlineAssembly/constant_array.sol

@@ -7,4 +7,4 @@ contract C {
     }
 }
 // ----
-// TypeError: (115-116): Only direct number constants are supported by inline assembly.
+// TypeError: (115-116): Only direct number constants and references to such constants are supported by inline assembly.

test/libsolidity/syntaxTests/inlineAssembly/constant_bytes_ref.sol

@@ -0,0 +1,11 @@
+contract C {
+    bytes32 constant x = keccak256("abc");
+    bytes32 constant y = x;
+    function f() public pure returns (uint t) {
+        assembly {
+            t := y
+        }
+    }
+}
+// ----
+// TypeError: (168-169): Only direct number constants and references to such constants are supported by inline assembly.

test/libsolidity/syntaxTests/inlineAssembly/constant_ref.sol

@@ -8,4 +8,3 @@ contract C {
     }
 }
 // ----
-// TypeError: (134-135): Only direct number constants are supported by inline assembly.