From 765ed13814b7547cc8c337b09d5bda098269e697 Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Mon, 9 Nov 2020 17:12:29 +0100
Subject: [PATCH] Immutables with literal values are pure.

---
 Changelog.md                                           |  1 +
 libsolidity/analysis/ViewPureChecker.cpp               | 10 ++++++++--
 .../standard_immutable_references/input.json           |  2 +-
 .../standard_immutable_references/output.json          |  2 +-
 .../syntaxTests/immutable/unrelated_reading.sol        |  2 +-
 .../syntaxTests/viewPureChecker/immutable.sol          |  1 -
 6 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/Changelog.md b/Changelog.md
index 949eeff1f..b566dd52e 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -2,6 +2,7 @@
 
 Language Features:
  * Ability to select the abi coder using ``pragma abicoder v1`` and ``pragma abicoder v2``.
+ * Immutable variables with literal number values are considered pure.
 
 Compiler Features:
  * SMTChecker: Add division by zero checks in the CHC engine.
diff --git a/libsolidity/analysis/ViewPureChecker.cpp b/libsolidity/analysis/ViewPureChecker.cpp
index f684bc289..a5ec40eb4 100644
--- a/libsolidity/analysis/ViewPureChecker.cpp
+++ b/libsolidity/analysis/ViewPureChecker.cpp
@@ -186,7 +186,13 @@ void ViewPureChecker::endVisit(Identifier const& _identifier)
 	bool writes = _identifier.annotation().willBeWrittenTo;
 	if (VariableDeclaration const* varDecl = dynamic_cast<VariableDeclaration const*>(declaration))
 	{
-		if (varDecl->isStateVariable() && !varDecl->isConstant())
+		if (varDecl->immutable())
+		{
+			// Immutables that are assigned literals are pure.
+			if (!(varDecl->value() && varDecl->value()->annotation().type->category() == Type::Category::RationalNumber))
+				mutability = StateMutability::View;
+		}
+		else if (varDecl->isStateVariable() && !varDecl->isConstant())
 			mutability = writes ? StateMutability::NonPayable : StateMutability::View;
 	}
 	else if (MagicVariableDeclaration const* magicVar = dynamic_cast<MagicVariableDeclaration const*>(declaration))
@@ -291,7 +297,7 @@ void ViewPureChecker::reportMutability(
 		m_currentFunction->stateMutability() == StateMutability::Pure ||
 		m_currentFunction->stateMutability() == StateMutability::NonPayable,
 		""
-				);
+	);
 }
 
 ViewPureChecker::MutabilityAndLocation const& ViewPureChecker::modifierMutability(
diff --git a/test/cmdlineTests/standard_immutable_references/input.json b/test/cmdlineTests/standard_immutable_references/input.json
index d81365c8a..6103dbed8 100644
--- a/test/cmdlineTests/standard_immutable_references/input.json
+++ b/test/cmdlineTests/standard_immutable_references/input.json
@@ -2,7 +2,7 @@
  "language": "Solidity",
  "sources": {
   "a.sol": {
-   "content": "// SPDX-License-Identifier: GPL-3.0\ncontract A { uint256 immutable x = 1; function f() public view returns (uint256) { return x; } }"
+   "content": "// SPDX-License-Identifier: GPL-3.0\ncontract A { uint256 immutable x = 1 + 3; function f() public pure returns (uint256) { return x; } }"
   }
  },
  "settings": {
diff --git a/test/cmdlineTests/standard_immutable_references/output.json b/test/cmdlineTests/standard_immutable_references/output.json
index 25537229f..2e17184ef 100644
--- a/test/cmdlineTests/standard_immutable_references/output.json
+++ b/test/cmdlineTests/standard_immutable_references/output.json
@@ -1,2 +1,2 @@
-{"contracts":{"a.sol":{"A":{"evm":{"deployedBytecode":{"generatedSources":[],"immutableReferences":{"3":[{"length":32,"start":77}]},"linkReferences":{},"object":"<BYTECODE REMOVED>","opcodes":"<OPCODES REMOVED>","sourceMap":"36:96:0:-:0;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;74:56;;;:::i;:::-;;;;;;;;;;;;;;;;;;;;108:7;126:1;119:8;;74:56;:::o"}}}}},"errors":[{"component":"general","errorCode":"3420","formattedMessage":"a.sol: Warning: Source file does not specify required compiler version!
+{"contracts":{"a.sol":{"A":{"evm":{"deployedBytecode":{"generatedSources":[],"immutableReferences":{"5":[{"length":32,"start":77}]},"linkReferences":{},"object":"<BYTECODE REMOVED>","opcodes":"<OPCODES REMOVED>","sourceMap":"36:100:0:-:0;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;78:56;;;:::i;:::-;;;;;;;;;;;;;;;;;;;;112:7;130:1;123:8;;78:56;:::o"}}}}},"errors":[{"component":"general","errorCode":"3420","formattedMessage":"a.sol: Warning: Source file does not specify required compiler version!
 ","message":"Source file does not specify required compiler version!","severity":"warning","sourceLocation":{"end":-1,"file":"a.sol","start":-1},"type":"Warning"}],"sources":{"a.sol":{"id":0}}}
diff --git a/test/libsolidity/syntaxTests/immutable/unrelated_reading.sol b/test/libsolidity/syntaxTests/immutable/unrelated_reading.sol
index 2b5614650..8eac18c7a 100644
--- a/test/libsolidity/syntaxTests/immutable/unrelated_reading.sol
+++ b/test/libsolidity/syntaxTests/immutable/unrelated_reading.sol
@@ -1,7 +1,7 @@
 contract C {
     uint immutable x = 1;
 
-    function readX() internal view returns(uint) {
+    function readX() internal pure returns(uint) {
         return x + 3;
     }
 }
diff --git a/test/libsolidity/syntaxTests/viewPureChecker/immutable.sol b/test/libsolidity/syntaxTests/viewPureChecker/immutable.sol
index 2ef5d1023..a1081959e 100644
--- a/test/libsolidity/syntaxTests/viewPureChecker/immutable.sol
+++ b/test/libsolidity/syntaxTests/viewPureChecker/immutable.sol
@@ -5,4 +5,3 @@ contract B {
     }
 }
 // ----
-// TypeError 2527: (100-101): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".