fix: check the start time in SablierV2LockupLinear._calculateStreamed…

…Amount (#941)

test: test streamedAmountOf when cliff time is zero and the stream is
PENDING
test: correct tree branches in streamedAmountOf

src/SablierV2LockupLinear.sol

@@ -187,10 +187,12 @@ contract SablierV2LockupLinear is
     /// - $d$ is the deposited amount.
     /// - $c$ is the cliff amount.
     function _calculateStreamedAmount(uint256 streamId) internal view override returns (uint128) {
-        // If the cliff time is in the future, return zero.
         uint256 cliffTime = uint256(_cliffs[streamId]);
+        uint256 startTime = uint256(_streams[streamId].startTime);
         uint256 blockTimestamp = block.timestamp;
-        if (cliffTime > blockTimestamp) {
+
+        // If the cliff time or the start time is in the future, return zero.
+        if (cliffTime > blockTimestamp || startTime > blockTimestamp) {
             return 0;
         }
 
@@ -204,7 +206,6 @@ contract SablierV2LockupLinear is
         // because there is no mix of amounts with different decimals.
         unchecked {
             // Calculate how much time has passed since the stream started, and the stream's total duration.
-            uint256 startTime = uint256(_streams[streamId].startTime);
             UD60x18 elapsedTime = ud(blockTimestamp - startTime);
             UD60x18 totalDuration = ud(endTime - startTime);
 

test/integration/concrete/lockup-linear/streamed-amount-of/streamedAmountOf.t.sol

@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: UNLICENSED
 pragma solidity >=0.8.22 <0.9.0;
 
+import { LockupLinear } from "src/types/DataTypes.sol";
+
 import { LockupLinear_Integration_Concrete_Test } from "../LockupLinear.t.sol";
 import { StreamedAmountOf_Integration_Concrete_Test } from "../../lockup/streamed-amount-of/streamedAmountOf.t.sol";
 
@@ -17,7 +19,28 @@ contract StreamedAmountOf_LockupLinear_Integration_Concrete_Test is
         StreamedAmountOf_Integration_Concrete_Test.setUp();
     }
 
-    function test_StreamedAmountOf_CliffTimeInThePast()
+    modifier givenStatusPendind() {
+        _;
+    }
+
+    function test_StreamedAmountOf_CliffTimeZero()
+        external
+        givenNotNull
+        givenStreamHasNotBeenCanceled
+        givenStatusPendind
+    {
+        vm.warp({ newTimestamp: defaults.START_TIME() - 1 });
+
+        LockupLinear.Timestamps memory timestamps = defaults.lockupLinearTimestamps();
+        timestamps.cliff = 0;
+        uint256 streamId = createDefaultStreamWithTimestamps(timestamps);
+
+        uint128 actualStreamedAmount = lockupLinear.streamedAmountOf(streamId);
+        uint128 expectedStreamedAmount = 0;
+        assertEq(actualStreamedAmount, expectedStreamedAmount, "streamedAmount");
+    }
+
+    function test_StreamedAmountOf_CliffTimeInTheFuture()
         external
         view
         givenNotNull
@@ -41,7 +64,7 @@ contract StreamedAmountOf_LockupLinear_Integration_Concrete_Test is
         assertEq(actualStreamedAmount, expectedStreamedAmount, "streamedAmount");
     }
 
-    function test_StreamedAmountOf_CliffTimeInTheFuture()
+    function test_StreamedAmountOf_CliffTimeInThePast()
         external
         givenNotNull
         givenStreamHasNotBeenCanceled

test/integration/concrete/lockup-linear/streamed-amount-of/streamedAmountOf.tree

@@ -1,8 +1,11 @@
 streamedAmountOf.t.sol
+├── given the stream's status is "PENDING"
+│  └── given the cliff time is zero
+│     └── it should return zero
 └── given the stream's status is "STREAMING"
-   ├── given the cliff time is in the past
+   ├── given the cliff time is in the future
    │  └── it should return zero
    ├── given the cliff time is in the present
    │  └── it should return the correct streamed amount
-   └── given the cliff time is in the future
+   └── given the cliff time is in the past
       └── it should return the correct streamed amount