Allow to distinguish out of gas from other traps (#4883)

* contracts: Allow to distinguish out of gas from other traps

When a contract encounters a runtime error a wasm trap is
triggered and the execution is halted. Currently, no matter
what was the cause for the trap it is always reported as:
DispatchError::Other("contract trapped during execution").

However, the trap that is triggered if a contract exhausts
its gas budget is particulary interesting. Therefore we add
a seperate error message for this cause:
DispatchError::Other("ran out of gas during contract execution").

A test is added hat executes a contract that never terminates.
Therefore it always exhausts is gas budget.

* fixup! contracts: Allow to distinguish out of gas from other traps

Remove overlong lines.

* fixup! contracts: Allow to distinguish out of gas from other traps

Rename Contract to Contracts

substrate/frame/contracts/src/tests.rs

@@ -722,6 +722,51 @@ fn dispatch_call_not_dispatched_after_top_level_transaction_failure() {
 	});
 }
 
+const CODE_RUN_OUT_OF_GAS: &str = r#"
+(module
+	(func (export "call")
+		(loop $inf (br $inf)) ;; just run out of gas
+		(unreachable)
+	)
+	(func (export "deploy"))
+)
+"#;
+
+#[test]
+fn run_out_of_gas() {
+	let (wasm, code_hash) = compile_module::<Test>(CODE_RUN_OUT_OF_GAS).unwrap();
+
+	ExtBuilder::default()
+		.existential_deposit(50)
+		.build()
+		.execute_with(|| {
+			Balances::deposit_creating(&ALICE, 1_000_000);
+
+			assert_ok!(Contracts::put_code(Origin::signed(ALICE), 100_000, wasm));
+
+			assert_ok!(Contracts::instantiate(
+				Origin::signed(ALICE),
+				100,
+				100_000,
+				code_hash.into(),
+				vec![],
+			));
+
+			// Call the contract with a fixed gas limit. It must run out of gas because it just
+			// loops forever.
+			assert_err!(
+				Contracts::call(
+					Origin::signed(ALICE),
+					BOB, // newly created account
+					0,
+					1000,
+					vec![],
+				),
+				"ran out of gas during contract execution"
+			);
+		});
+}
+
 const CODE_SET_RENT: &str = r#"
 (module
 	(import "env" "ext_dispatch_call" (func $ext_dispatch_call (param i32 i32)))