Adds syntax tests, documentation and changelog entry.

Refines comment for array utility function.

Changelog.md

@@ -1,5 +1,7 @@
 ### 0.5.0 (unreleased)
 
+Language Features:
+ * General: Support ``pop()`` for storage arrays.
 
 Breaking Changes:
  * Disallow conversions between bytesX and uintY of different size.

docs/types.rst

@@ -682,7 +682,7 @@ possible:
 It is planned to remove this restriction in the future but currently creates
 some complications because of how arrays are passed in the ABI.
 
-.. index:: ! array;length, length, push, !array;push
+.. index:: ! array;length, length, push, pop, !array;push, !array;pop
 
 Members
 ^^^^^^^
@@ -693,6 +693,8 @@ Members
     ``.length`` member. This does not happen automatically when attempting to access elements outside the current length. The size of memory arrays is fixed (but dynamic, i.e. it can depend on runtime parameters) once they are created.
 **push**:
      Dynamic storage arrays and ``bytes`` (not ``string``) have a member function called ``push`` that can be used to append an element at the end of the array. The function returns the new length.
+**pop**:
+     Dynamic storage arrays and ``bytes`` (not ``string``) have a member function called ``pop`` that can be used to remove an element from the end of the array.
 
 .. warning::
     It is not yet possible to use arrays of arrays in external functions.

libsolidity/codegen/ArrayUtils.cpp

@@ -840,7 +840,7 @@ void ArrayUtils::popStorageArrayElement(ArrayType const& _type) const
 				let length := and(div(slot_value, 2), 0x1f)
 				if iszero(length) { invalid() }
 
-				// Zero-out the suffix inlcluding the least significant byte.
+				// Zero-out the suffix including the least significant byte.
 				let mask := sub(exp(0x100, sub(33, length)), 1)
 				length := sub(length, 1)
 				slot_value := or(and(not(mask), slot_value), mul(length, 2))

libsolidity/codegen/ArrayUtils.h

@@ -73,7 +73,7 @@ public:
 	/// Stack pre: reference (excludes byte offset)
 	/// Stack post: new_length
 	void incrementDynamicArraySize(ArrayType const& _type) const;
-	/// Decrements the size of a dynamic array by one if length is nonzero. Returns otherwise.
+	/// Decrements the size of a dynamic array by one if length is nonzero. Causes an invalid instruction otherwise.
 	/// Clears the removed data element. In case of a byte array, this might move the data.
 	/// Stack pre: reference
 	/// Stack post:

test/libsolidity/syntaxTests/array/array_pop.sol

@@ -0,0 +1,7 @@
+contract C {
+    uint[] data;
+    function test() public {
+      data.pop();
+    }
+}
+// ----

test/libsolidity/syntaxTests/array/array_pop_arg.sol

@@ -0,0 +1,8 @@
+contract C {
+    uint[] data;
+    function test() public {
+      data.pop(5);
+    }
+}
+// ----
+// TypeError: (65-76): Wrong argument count for function call: 1 arguments given but expected 0.

test/libsolidity/syntaxTests/array/bytes_pop.sol

@@ -0,0 +1,7 @@
+contract C {
+    bytes data;
+    function test() public {
+      data.pop();
+    }
+}
+// ----

test/libsolidity/syntaxTests/array/dynamic_memory_array_pop.sol

@@ -0,0 +1,8 @@
+contract C {
+    function test() public {
+      uint[] memory data;
+      data.pop();
+    }
+}
+// ----
+// TypeError: (74-82): Member "pop" is not available in uint256[] memory outside of storage.

test/libsolidity/syntaxTests/array/no_array_pop.sol

@@ -0,0 +1,8 @@
+contract C {
+    uint data;
+    function test() public {
+      data.pop();
+    }
+}
+// ----
+// TypeError: (63-71): Member "pop" not found or not visible after argument-dependent lookup in uint256

test/libsolidity/syntaxTests/array/static_storage_array_pop.sol

@@ -0,0 +1,8 @@
+contract C {
+    uint[3] data;
+    function test() public {
+      data.pop();
+    }
+}
+// ----
+// TypeError: (66-74): Member "pop" not found or not visible after argument-dependent lookup in uint256[3] storage ref

test/libsolidity/syntaxTests/array/string_pop.sol

@@ -0,0 +1,8 @@
+contract C {
+    string data;
+    function test() public {
+      data.pop();
+    }
+}
+// ----
+// TypeError: (65-73): Member "pop" not found or not visible after argument-dependent lookup in string storage ref