Turn warning about uninitialized storage returns into an error.

Changelog.md

@@ -17,6 +17,7 @@ Breaking Changes:
  * Commandline interface: Remove obsolete ``--formal`` option.
  * Commandline interface: Rename the ``--julia`` option to ``--yul``.
  * Commandline interface: Require ``-`` if standard input is used as source.
+ * Control Flow Analyzer: Turn warning about returning uninitialized storage pointers into an error.
  * General: ``continue`` in a ``do...while`` loop jumps to the condition (it used to jump to the loop body). Warning: this may silently change the semantics of existing code.
  * General: Disallow declaring empty structs.
  * General: Disallow raw ``callcode`` (was already deprecated in 0.4.12). It is still possible to use it via inline assembly.

libsolidity/analysis/ControlFlowAnalyzer.cpp

@@ -144,12 +144,12 @@ void ControlFlowAnalyzer::checkUnassignedStorageReturnValues(
 						ssl.append("Problematic end of function:", _function.location());
 				}
 
-			m_errorReporter.warning(
+			m_errorReporter.typeError(
 				returnVal->location(),
-				"This variable is of storage pointer type and might be returned without assignment. "
+				ssl,
-				"This can cause storage corruption. Assign the variable (potentially from itself) "
+				"This variable is of storage pointer type and might be returned without assignment and "
-				"to remove this warning.",
+				"could be used uninitialized. Assign the variable (potentially from itself) "
-				ssl
+				"to fix this error."
 			);
 		}
 	}

test/libsolidity/SolidityABIJSON.cpp

@@ -756,7 +756,7 @@ BOOST_AUTO_TEST_CASE(library_function)
 	char const* sourceCode = R"(
 		library test {
 			struct StructType { uint a; }
-			function f(StructType storage b, uint[] storage c, test d) public returns (uint[] memory e, StructType storage f) {}
+			function f(StructType storage b, uint[] storage c, test d) public returns (uint[] memory e, StructType storage f) { f = f; }
 		}
 	)";
 

test/libsolidity/syntaxTests/controlFlow/storageReturn/assembly_err.sol

@@ -0,0 +1,10 @@
+contract C {
+    struct S { bool f; }
+    S s;
+    function f() internal pure returns (S storage) {
+        assembly {
+        }
+    }
+}
+// ----
+// TypeError: (87-88): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/assembly_fine.sol

@@ -8,7 +8,7 @@ contract C {
     }
     function g(bool flag) internal returns (S storage c) {
         // control flow in assembly will not be analyzed for now,
-        // so this will not issue a warning
+        // so this will not issue an error
         assembly {
             if flag {
                 sstore(c_slot, sload(s_slot))
@@ -17,7 +17,7 @@ contract C {
     }
     function h() internal returns (S storage c) {
         // any reference from assembly will be sufficient for now,
-        // so this will not issue a warning
+        // so this will not issue an error
         assembly {
             sstore(s_slot, sload(c_slot))
         }

test/libsolidity/syntaxTests/controlFlow/storageReturn/assembly_warn.sol

@@ -1,10 +0,0 @@
-contract C {
-    struct S { bool f; }
-    S s;
-    function f() internal pure returns (S storage) {
-        assembly {
-        }
-    }
-}
-// ----
-// Warning: (87-88): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.

test/libsolidity/syntaxTests/controlFlow/storageReturn/dowhile_err.sol

@@ -0,0 +1,52 @@
+contract C {
+    struct S { bool f; }
+    S s;
+    function f() internal view returns (S storage c) {
+        do {
+            break;
+            c = s;
+        } while(false);
+    }
+    function g() internal view returns (S storage c) {
+        do {
+            if (s.f) {
+                continue;
+                c = s;
+            }
+            else {
+            }
+        } while(false);
+    }
+    function h() internal view returns (S storage c) {
+        do {
+            if (s.f) {
+                break;
+            }
+            else {
+                c = s;
+            }
+        } while(false);
+    }
+    function i() internal view returns (S storage c) {
+        do {
+            if (s.f) {
+                continue;
+            }
+            else {
+                c = s;
+            }
+        } while(false);
+    }
+    function j() internal view returns (S storage c) {
+        do {
+            continue;
+            c = s;
+        } while(false);
+    }
+}
+// ----
+// TypeError: (87-98): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (223-234): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (440-451): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (654-665): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (871-882): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/dowhile_warn.sol

@@ -1,52 +0,0 @@
-contract C {
-    struct S { bool f; }
-    S s;
-    function f() internal view returns (S storage c) {
-        do {
-            break;
-            c = s;
-        } while(false);
-    }
-    function g() internal view returns (S storage c) {
-        do {
-            if (s.f) {
-                continue;
-                c = s;
-            }
-            else {
-            }
-        } while(false);
-    }
-    function h() internal view returns (S storage c) {
-        do {
-            if (s.f) {
-                break;
-            }
-            else {
-                c = s;
-            }
-        } while(false);
-    }
-    function i() internal view returns (S storage c) {
-        do {
-            if (s.f) {
-                continue;
-            }
-            else {
-                c = s;
-            }
-        } while(false);
-    }
-    function j() internal view returns (S storage c) {
-        do {
-            continue;
-            c = s;
-        } while(false);
-    }
-}
-// ----
-// Warning: (87-98): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (223-234): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (440-451): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (654-665): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (871-882): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.

test/libsolidity/syntaxTests/controlFlow/storageReturn/emptyReturn_err.sol

@@ -0,0 +1,14 @@
+contract C {
+    struct S { bool f; }
+    S s;
+    function f() internal pure returns (S storage) { return; }
+    function g() internal view returns (S storage c, S storage) { c = s; return; }
+    function h() internal view returns (S storage, S storage d) { d = s; return; }
+    function i() internal pure returns (S storage, S storage) { return; }
+}
+// ----
+// TypeError: (87-88): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (163-164): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (233-234): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (316-317): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (327-328): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/emptyReturn_fine.sol

@@ -2,5 +2,6 @@ contract C {
     struct S { bool f; }
     S s;
     function f() internal view returns (S storage c, S storage d) { c = s; d = s; return; }
+    function g() internal view returns (S storage, S storage) { return (s,s); }
 }
 // ----

test/libsolidity/syntaxTests/controlFlow/storageReturn/emptyReturn_warn.sol

@@ -1,15 +0,0 @@
-contract C {
-    struct S { bool f; }
-    S s;
-    function f() internal pure returns (S storage) { return; }
-    function g() internal view returns (S storage c, S storage) { c = s; return; }
-    function h() internal view returns (S storage, S storage d) { d = s; return; }
-    function i() internal pure returns (S storage, S storage) { return; }
-    function j() internal view returns (S storage, S storage) { return (s,s); }
-}
-// ----
-// Warning: (87-88): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (163-164): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (233-234): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (316-317): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (327-328): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.

test/libsolidity/syntaxTests/controlFlow/storageReturn/for_err.sol

@@ -0,0 +1,16 @@
+contract C {
+    struct S { bool f; }
+    S s;
+    function f() internal view returns (S storage c) {
+        for(;; c = s) {
+        }
+    }
+    function g() internal view returns (S storage c) {
+        for(;;) {
+            c = s;
+        }
+    }
+}
+// ----
+// TypeError: (87-98): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (182-193): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/for_warn.sol

@@ -1,16 +0,0 @@
-contract C {
-    struct S { bool f; }
-    S s;
-    function f() internal view returns (S storage c) {
-        for(;; c = s) {
-        }
-    }
-    function g() internal view returns (S storage c) {
-        for(;;) {
-            c = s;
-        }
-    }
-}
-// ----
-// Warning: (87-98): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (182-193): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.

test/libsolidity/syntaxTests/controlFlow/storageReturn/if_err.sol

@@ -0,0 +1,18 @@
+contract C {
+    struct S { bool f; }
+    S s;
+    function f(bool flag) internal view returns (S storage c) {
+        if (flag) c = s;
+    }
+    function g(bool flag) internal returns (S storage c) {
+        if (flag) c = s;
+        else
+        {
+            if (!flag) c = s;
+            else s.f = true;
+        }
+    }
+}
+// ----
+// TypeError: (96-107): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (186-197): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/if_warn.sol

@@ -1,18 +0,0 @@
-contract C {
-    struct S { bool f; }
-    S s;
-    function f(bool flag) internal view returns (S storage c) {
-        if (flag) c = s;
-    }
-    function g(bool flag) internal returns (S storage c) {
-        if (flag) c = s;
-        else
-        {
-            if (!flag) c = s;
-            else s.f = true;
-        }
-    }
-}
-// ----
-// Warning: (96-107): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (186-197): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.

test/libsolidity/syntaxTests/controlFlow/storageReturn/modifier_err.sol

@@ -0,0 +1,22 @@
+contract C {
+    modifier revertIfNoReturn() {
+        _;
+        revert();
+    }
+    modifier ifFlag(bool flag) {
+        if (flag)
+            _;
+    }
+    struct S { uint a; }
+    S s;
+    function f(bool flag) ifFlag(flag) internal view returns(S storage) {
+        return s;
+    }
+
+    function g(bool flag) ifFlag(flag) revertIfNoReturn() internal view returns(S storage) {
+        return s;
+    }
+}
+// ----
+// TypeError: (249-250): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (367-368): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/modifier_warn.sol

@@ -1,22 +0,0 @@
-contract C {
-    modifier revertIfNoReturn() {
-        _;
-        revert();
-    }
-    modifier ifFlag(bool flag) {
-        if (flag)
-            _;
-    }
-    struct S { uint a; }
-    S s;
-    function f(bool flag) ifFlag(flag) internal view returns(S storage) {
-        return s;
-    }
-
-    function g(bool flag) ifFlag(flag) revertIfNoReturn() internal view returns(S storage) {
-        return s;
-    }
-}
-// ----
-// Warning: (249-250): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (367-368): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.

test/libsolidity/syntaxTests/controlFlow/storageReturn/short_circuit_err.sol

@@ -0,0 +1,18 @@
+contract C {
+    struct S { bool f; }
+    S s;
+    function f() internal view returns (S storage c) {
+        false && (c = s).f;
+    }
+    function g() internal view returns (S storage c) {
+        true || (c = s).f;
+    }
+    function h() internal view returns (S storage c) {
+        // expect error, although this is always fine
+        true && (false || (c = s).f);
+    }
+}
+// ----
+// TypeError: (87-98): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (176-187): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (264-275): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/short_circuit_warn.sol

@@ -1,18 +0,0 @@
-contract C {
-    struct S { bool f; }
-    S s;
-    function f() internal view returns (S storage c) {
-        false && (c = s).f;
-    }
-    function g() internal view returns (S storage c) {
-        true || (c = s).f;
-    }
-    function h() internal view returns (S storage c) {
-        // expect warning, although this is always fine
-        true && (false || (c = s).f);
-    }
-}
-// ----
-// Warning: (87-98): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (176-187): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (264-275): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.

test/libsolidity/syntaxTests/controlFlow/storageReturn/ternary_err.sol

@@ -0,0 +1,13 @@
+contract C {
+    struct S { bool f; }
+    S s;
+    function f(bool flag) internal view returns (S storage c) {
+        flag ? (c = s).f : false;
+    }
+    function g(bool flag) internal view returns (S storage c) {
+        flag ? false : (c = s).f;
+    }
+}
+// ----
+// TypeError: (96-107): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.
+// TypeError: (200-211): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/ternary_warn.sol

@@ -1,13 +0,0 @@
-contract C {
-    struct S { bool f; }
-    S s;
-    function f(bool flag) internal view returns (S storage c) {
-        flag ? (c = s).f : false;
-    }
-    function g(bool flag) internal view returns (S storage c) {
-        flag ? false : (c = s).f;
-    }
-}
-// ----
-// Warning: (96-107): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.
-// Warning: (200-211): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.

test/libsolidity/syntaxTests/controlFlow/storageReturn/while_err.sol

@@ -0,0 +1,11 @@
+contract C {
+    struct S { bool f; }
+    S s;
+    function f() internal view returns (S storage c) {
+        while(false) {
+            c = s;
+        }
+    }
+}
+// ----
+// TypeError: (87-98): This variable is of storage pointer type and might be returned without assignment and could be used uninitialized. Assign the variable (potentially from itself) to fix this error.

test/libsolidity/syntaxTests/controlFlow/storageReturn/while_warn.sol

@@ -1,11 +0,0 @@
-contract C {
-    struct S { bool f; }
-    S s;
-    function f() internal view returns (S storage c) {
-        while(false) {
-            c = s;
-        }
-    }
-}
-// ----
-// Warning: (87-98): This variable is of storage pointer type and might be returned without assignment. This can cause storage corruption. Assign the variable (potentially from itself) to remove this warning.