Make error message less confusing

libsolidity/analysis/ViewPureChecker.cpp

@@ -256,10 +256,9 @@ void ViewPureChecker::reportMutability(
 		m_errorReporter.typeError(
 			8961_error,
 			_location,
-			"Function declared as " +
+			"Function cannot be declared as " +
 			stateMutabilityToString(m_currentFunction->stateMutability()) +
-			", but this expression (potentially) modifies the state and thus "
-			"requires non-payable (the default) or payable."
+			" because this expression (potentially) modifies the state."
 		);
 		m_errors = true;
 	}

test/libsolidity/syntaxTests/freeFunctions/free_mutability.sol

@@ -5,4 +5,4 @@ function f() {
 function g(uint[] storage x) pure { x[0] = 1; }
 // ----
 // Warning 2018: (0-39): Function state mutability can be restricted to pure
-// TypeError 8961: (76-80): Function declared as pure, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (76-80): Function cannot be declared as pure because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/multiSource/one_source.sol

@@ -4,4 +4,4 @@ contract A {
 	function f() public pure { x = 42; }
 }
 // ----
-// TypeError 8961: (SourceName:53-54): Function declared as pure, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (SourceName:53-54): Function cannot be declared as pure because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/access_to_base_member_function.sol

@@ -8,4 +8,4 @@ contract B is A {
     }
 }
 // ----
-// TypeError 8961: (100-105): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (100-105): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/access_to_base_member_struct.sol

@@ -15,7 +15,7 @@ contract B is A {
     }
 }
 // ----
-// TypeError 8961: (107-110): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
-// TypeError 8961: (166-171): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (107-110): Function cannot be declared as view because this expression (potentially) modifies the state.
+// TypeError 8961: (166-171): Function cannot be declared as view because this expression (potentially) modifies the state.
 // TypeError 2527: (244-247): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
 // TypeError 2527: (244-249): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".

test/libsolidity/syntaxTests/viewPureChecker/access_to_base_members.sol

@@ -12,4 +12,4 @@ contract B is A {
 }
 // ----
 // TypeError 2527: (107-110): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError 8961: (157-160): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (157-160): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/array/access_to_array_push_view.sol

@@ -5,4 +5,4 @@ contract A {
     }
 }
 // ----
-// TypeError 8961: (88-96): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (88-96): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/builtin_functions_view_fail.sol

@@ -20,8 +20,8 @@ contract C {
     }
 }
 // ----
-// TypeError 8961: (52-77): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
-// TypeError 8961: (132-153): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
-// TypeError 8961: (201-228): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
-// TypeError 8961: (293-323): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
-// TypeError 8961: (414-436): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (52-77): Function cannot be declared as view because this expression (potentially) modifies the state.
+// TypeError 8961: (132-153): Function cannot be declared as view because this expression (potentially) modifies the state.
+// TypeError 8961: (201-228): Function cannot be declared as view because this expression (potentially) modifies the state.
+// TypeError 8961: (293-323): Function cannot be declared as view because this expression (potentially) modifies the state.
+// TypeError 8961: (414-436): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/call_internal_functions_fail.sol

@@ -7,4 +7,4 @@ contract C {
 }
 // ----
 // TypeError 2527: (56-59): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError 8961: (130-133): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (130-133): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/creation_view_fail.sol

@@ -3,4 +3,4 @@ contract C {
     function f() public view { new D(); }
 }
 // ----
-// TypeError 8961: (58-65): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (58-65): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/function_types_fail.sol

@@ -13,6 +13,6 @@ contract C {
     }
 }
 // ----
-// TypeError 8961: (92-103): Function declared as pure, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (92-103): Function cannot be declared as pure because this expression (potentially) modifies the state.
 // TypeError 2527: (193-202): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError 8961: (289-300): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (289-300): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/gas_with_call_nonpayable.sol

@@ -8,5 +8,5 @@ contract C {
 	}
 }
 // ----
-// TypeError 8961: (90-109): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
-// TypeError 8961: (180-197): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (90-109): Function cannot be declared as view because this expression (potentially) modifies the state.
+// TypeError 8961: (180-197): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/local_storage_variables_fail.sol

@@ -12,4 +12,4 @@ contract C {
 }
 // ----
 // TypeError 2527: (100-101): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError 8961: (184-187): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (184-187): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/modifiers_fail.sol

@@ -9,4 +9,4 @@ contract C is D {
 }
 // ----
 // TypeError 2527: (154-162): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError 8961: (195-209): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (195-209): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/value_with_call_nonpayable.sol

@@ -8,5 +8,5 @@ contract C {
 	}
 }
 // ----
-// TypeError 8961: (90-111): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
-// TypeError 8961: (182-201): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (90-111): Function cannot be declared as view because this expression (potentially) modifies the state.
+// TypeError 8961: (182-201): Function cannot be declared as view because this expression (potentially) modifies the state.

test/libsolidity/syntaxTests/viewPureChecker/write_storage_fail.sol

@@ -3,4 +3,4 @@ contract C {
     function f() view public { x = 2; }
 }
 // ----
-// TypeError 8961: (56-57): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError 8961: (56-57): Function cannot be declared as view because this expression (potentially) modifies the state.