Add test for extcodesize check.

test/libsolidity/semanticTests/functionCall/external_call_at_construction_time.sol

@@ -0,0 +1,28 @@
+pragma solidity >= 0.6.0;
+
+// This tests skipping the extcodesize check.
+
+contract T {
+    constructor() { this.f(); }
+    function f() external {}
+}
+contract U {
+    constructor() { this.f(); }
+    function f() external returns (uint) {}
+}
+
+contract C {
+    function f(uint c) external returns (uint) {
+        if (c == 0) new T();
+        else if (c == 1) new U();
+        return 1 + c;
+    }
+}
+
+// ====
+// EVMVersion: >=byzantium
+// compileViaYul: also
+// ----
+// f(uint256): 0 -> FAILURE
+// f(uint256): 1 -> FAILURE
+// f(uint256): 2 -> 3

test/libsolidity/semanticTests/functionCall/external_call_to_nonexisting.sol

@@ -0,0 +1,36 @@
+// This tests skipping the extcodesize check.
+
+interface I {
+    function a() external pure;
+    function b() external;
+    function c() external payable;
+    function x() external returns (uint);
+    function y() external returns (string memory);
+}
+contract C {
+    I i = I(address(0xcafecafe));
+    constructor() payable {}
+    function f(uint c) external returns (uint) {
+        if (c == 0) i.a();
+        else if (c == 1) i.b();
+        else if (c == 2) i.c();
+        else if (c == 3) i.c{value: 1}();
+        else if (c == 4) i.x();
+        else if (c == 5) i.y();
+        return 1 + c;
+    }
+}
+
+// ====
+// compileViaYul: also
+// ----
+// constructor(), 1 ether ->
+// gas legacy: 465314
+// gas legacyOptimized: 510004
+// f(uint256): 0 -> FAILURE
+// f(uint256): 1 -> FAILURE
+// f(uint256): 2 -> FAILURE
+// f(uint256): 3 -> FAILURE
+// f(uint256): 4 -> FAILURE
+// f(uint256): 5 -> FAILURE
+// f(uint256): 6 -> 7

test/libsolidity/semanticTests/functionCall/external_call_to_nonexisting_debugstrings.sol

@@ -0,0 +1,39 @@
+pragma solidity >= 0.6.0;
+
+// This tests skipping the extcodesize check.
+
+interface I {
+    function a() external pure;
+    function b() external;
+    function c() external payable;
+    function x() external returns (uint);
+    function y() external returns (string memory);
+}
+contract C {
+    I i = I(address(0xcafecafe));
+    constructor() payable {}
+    function f(uint c) external returns (uint) {
+        if (c == 0) i.a();
+        else if (c == 1) i.b();
+        else if (c == 2) i.c();
+        else if (c == 3) i.c{value: 1}();
+        else if (c == 4) i.x();
+        else if (c == 5) i.y();
+        return 1 + c;
+    }
+}
+
+// ====
+// EVMVersion: >=byzantium
+// compileViaYul: also
+// revertStrings: debug
+// ----
+// constructor(), 1 ether ->
+// gas legacyOptimized: 510004
+// f(uint256): 0 -> FAILURE, hex"08c379a0", 0x20, 37, "Target contract does not contain", " code"
+// f(uint256): 1 -> FAILURE, hex"08c379a0", 0x20, 37, "Target contract does not contain", " code"
+// f(uint256): 2 -> FAILURE, hex"08c379a0", 0x20, 37, "Target contract does not contain", " code"
+// f(uint256): 3 -> FAILURE, hex"08c379a0", 0x20, 37, "Target contract does not contain", " code"
+// f(uint256): 4 -> FAILURE, hex"08c379a0", 0x20, 37, "Target contract does not contain", " code"
+// f(uint256): 5 -> FAILURE, hex"08c379a0", 0x20, 37, "Target contract does not contain", " code"
+// f(uint256): 6 -> 7

test/libsolidity/semanticTests/functionCall/precompile_extcodesize_check.sol

@@ -1,13 +1,21 @@
 interface Identity {
     function selectorAndAppendValue(uint value) external pure returns (uint);
 }
+interface ReturnMoreData {
+    function f(uint value) external pure returns (uint, uint, uint);
+}
 contract C {
     Identity constant i = Identity(address(0x0004));
     function testHighLevel() external pure returns (bool) {
-        // Should fail because `extcodesize(4) = 0`
+        // Works because the extcodesize check is skipped
+        // and the precompiled contract returns actual data.
         i.selectorAndAppendValue(5);
         return true;
     }
+    function testHighLevel2() external pure returns (uint, uint, uint) {
+        // Fails because the identity contract does not return enough data.
+        return ReturnMoreData(address(4)).f(2);
+    }
     function testLowLevel() external view returns (uint value) {
         (bool success, bytes memory ret) =
             address(4).staticcall(
@@ -23,3 +31,4 @@ contract C {
 // ----
 // testHighLevel() -> FAILURE
 // testLowLevel() -> 0xc76596d400000000000000000000000000000000000000000000000000000000
+// testHighLevel2() -> FAILURE