Sol -> Yul Generation: Implicit conversions

test/libsolidity/semanticTests/viaYul/implicit_cast_assignment.sol

@@ -0,0 +1,14 @@
+// Tests IRGeneratorForStatements::visit(Assignment const& _assignment)
+contract C {
+    function f() public pure returns (uint16 x) {
+        uint8 y;
+        assembly {
+            y := 0x12345678
+        }
+        x = y;
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// f() -> 0x78

test/libsolidity/semanticTests/viaYul/implicit_cast_function_call.sol

@@ -0,0 +1,17 @@
+// IRGeneratorForStatements::visit(FunctionCall const& _functionCall)
+contract C {
+    function f(uint b) public pure returns (uint x) {
+        x = b;
+    }
+    function g() public pure returns (uint x) {
+        uint8 a;
+        assembly {
+            a := 0x12345678
+        }
+        x = f(a);
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// g() -> 0x78

test/libsolidity/semanticTests/viaYul/implicit_cast_local_assignment.sol

@@ -0,0 +1,13 @@
+// IRGeneratorForStatements::visit(VariableDeclarationStatement const& _varDeclStatement)
+contract C {
+    function f() public pure returns (uint y) {
+        uint8 a;
+        assembly { a := 0x12345678 }
+        uint z = a;
+        y = z;
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// f() -> 0x78