Introduce deprecations towards v2

.github/workflows/ci.yml

@@ -37,7 +37,6 @@ jobs:
       with:
         platform: ${{ matrix.platform }}
         swift: ~${{ matrix.swift }}
-        warnings-as-errors: true
   linux:
     name: Linux (Swift ${{ matrix.swift }})
     runs-on: ubuntu-latest
@@ -53,4 +52,4 @@ jobs:
       image: swift:${{ matrix.swift }}
     steps:
     - uses: actions/checkout@v2
-    - run: swift test --enable-test-discovery --parallel -Xswiftc -warnings-as-errors
+    - run: swift test --enable-test-discovery --parallel

Sources/PreciseDecimal/PreciseDecimal.swift

@@ -3,29 +3,49 @@ import Foundation
 public struct PreciseDecimal {
     public var value: Decimal
 
+    @available(*, deprecated, message: "PreciseDecimal.init(_:) is deprecated and will be removed in version 2. Use PreciseDecimal.init(string:) instead.")
     public init<I: FixedWidthInteger>(_ value: I) {
         self.value = Decimal(precise: value)
     }
 
+    @available(*, deprecated, message: "PreciseDecimal.init(_:) loses precision past the 6th decimal place, so it is deprecated and will be removed in version 2. Use PreciseDecimal.init(string:) instead.")
     public init(_ value: Double) {
         self.value = Decimal(precise: value)
     }
+
+    public init?(string: String) {
+        guard let decimal = Decimal(string: string) else {
+            return nil
+        }
+        self.value = decimal
+    }
 }
 
 extension PreciseDecimal: Hashable {}
 
 extension PreciseDecimal: ExpressibleByIntegerLiteral {
+    @available(*, deprecated, message: "Initialization via integer literals is deprecated and will be removed in version 2. Use a String literal instead.")
     public init(integerLiteral value: IntegerLiteralType) {
         self.init(Double(value))
     }
 }
 
 extension PreciseDecimal: ExpressibleByFloatLiteral {
+    @available(*, deprecated, message: "Initialization via floating-point literals loses precision past the 6th decimal place, so it is deprecated and will be removed in version 2. Use a String literal instead.")
     public init(floatLiteral value: FloatLiteralType) {
         self.init(value)
     }
 }
 
+extension PreciseDecimal: ExpressibleByStringLiteral {
+    public init(stringLiteral value: StringLiteralType) {
+        guard let _self = Self(string: value) else {
+            fatalError("Invalid PreciseDecimal string literal: \(value)")
+        }
+        self = _self
+    }
+}
+
 extension PreciseDecimal: Codable {
     public init(from decoder: Decoder) throws {
         let container = try decoder.singleValueContainer()
@@ -43,13 +63,15 @@ extension PreciseDecimal: CustomDebugStringConvertible {
 }
 
 extension Decimal {
+    @available(*, deprecated, message: "PreciseDecimal.init(precise:) loses precision past the 6th decimal place, so it is deprecated and will be removed in version 2. Use PreciseDecimal.init(string:) instead.")
     public init<I: FixedWidthInteger>(precise value: I) {
         guard let decimal = Self(string: String(value)) else {
             preconditionFailure("Failed to convert FixedWidthInteger '\(value)' to Decimal")
         }
         self = decimal
     }
 
+    @available(*, deprecated, message: "PreciseDecimal.init(precise:) loses precision past the 6th decimal place, so it is deprecated and will be removed in version 2. Use PreciseDecimal.init(string:) instead.")
     public init(precise value: Double) {
         guard let decimal = Self(string: String(value)) else {
             preconditionFailure("Failed to convert Double '\(value)' to Decimal")

Tests/PreciseDecimalTests/InitTests.swift

@@ -2,7 +2,7 @@ import XCTest
 import PreciseDecimal
 
 final class InitTests: XCTestCase {
-    func testIntegers() {
+    func testIntegers() throws {
         assertInteger(0, "0")
         assertInteger(1, "1")
         assertInteger(2, "2")
@@ -32,9 +32,39 @@ final class InitTests: XCTestCase {
         assertLiteral(42, "42")
         assertLiteral(100, "100")
         assertLiteral(69420, "69420")
+
+        try assertString("0", "0")
+        try assertString("1", "1")
+        try assertString("2", "2")
+        try assertString("3", "3")
+        try assertString("4", "4")
+        try assertString("5", "5")
+        try assertString("6", "6")
+        try assertString("7", "7")
+        try assertString("8", "8")
+        try assertString("9", "9")
+        try assertString("10", "10")
+        try assertString("42", "42")
+        try assertString("100", "100")
+        try assertString("69420", "69420")
+
+        assertLiteral("0", "0")
+        assertLiteral("1", "1")
+        assertLiteral("2", "2")
+        assertLiteral("3", "3")
+        assertLiteral("4", "4")
+        assertLiteral("5", "5")
+        assertLiteral("6", "6")
+        assertLiteral("7", "7")
+        assertLiteral("8", "8")
+        assertLiteral("9", "9")
+        assertLiteral("10", "10")
+        assertLiteral("42", "42")
+        assertLiteral("100", "100")
+        assertLiteral("69420", "69420")
     }
 
-    func testOneDecimal() {
+    func testOneDecimal() throws {
         assertDouble(0.0, "0")
         assertDouble(0.2, "0.2")
         assertDouble(0.5, "0.5")
@@ -54,9 +84,29 @@ final class InitTests: XCTestCase {
         assertLiteral(1.5, "1.5")
         assertLiteral(420.6, "420.6")
         assertLiteral(42069.4, "42069.4")
+
+        try assertString("0.0", "0")
+        try assertString("0.2", "0.2")
+        try assertString("0.5", "0.5")
+        try assertString("0.7", "0.7")
+        try assertString("1.0", "1")
+        try assertString("1.2", "1.2")
+        try assertString("1.5", "1.5")
+        try assertString("420.6", "420.6")
+        try assertString("42069.4", "42069.4")
+
+        assertLiteral("0.0", "0")
+        assertLiteral("0.2", "0.2")
+        assertLiteral("0.5", "0.5")
+        assertLiteral("0.7", "0.7")
+        assertLiteral("1.0", "1")
+        assertLiteral("1.2", "1.2")
+        assertLiteral("1.5", "1.5")
+        assertLiteral("420.6", "420.6")
+        assertLiteral("42069.4", "42069.4")
     }
 
-    func testTwoDecimals() {
+    func testTwoDecimals() throws {
         assertDouble(0.00, "0")
         assertDouble(0.25, "0.25")
         assertDouble(0.50, "0.5")
@@ -72,9 +122,25 @@ final class InitTests: XCTestCase {
         assertLiteral(1.00, "1")
         assertLiteral(1.25, "1.25")
         assertLiteral(1.50, "1.5")
+
+        try assertString("0.00", "0")
+        try assertString("0.25", "0.25")
+        try assertString("0.50", "0.5")
+        try assertString("0.75", "0.75")
+        try assertString("1.00", "1")
+        try assertString("1.25", "1.25")
+        try assertString("1.50", "1.5")
+
+        assertLiteral("0.00", "0")
+        assertLiteral("0.25", "0.25")
+        assertLiteral("0.50", "0.5")
+        assertLiteral("0.75", "0.75")
+        assertLiteral("1.00", "1")
+        assertLiteral("1.25", "1.25")
+        assertLiteral("1.50", "1.5")
     }
 
-    func testThreeDecimals() {
+    func testThreeDecimals() throws {
         assertDouble(1.111, "1.111")
         assertDouble(2.222, "2.222")
         assertDouble(3.133, "3.133")
@@ -88,6 +154,24 @@ final class InitTests: XCTestCase {
         assertLiteral(3.333, "3.333")
         assertLiteral(69.420, "69.42")
         assertLiteral(69.421, "69.421")
+
+        try assertString("1.111", "1.111")
+        try assertString("2.222", "2.222")
+        try assertString("3.133", "3.133")
+        try assertString("3.333", "3.333")
+        try assertString("69.420", "69.42")
+        try assertString("69.421", "69.421")
+
+        assertLiteral("1.111", "1.111")
+        assertLiteral("2.222", "2.222")
+        assertLiteral("3.133", "3.133")
+        assertLiteral("3.333", "3.333")
+        assertLiteral("69.420", "69.42")
+        assertLiteral("69.421", "69.421")
+    }
+
+    func testInvalidInput() {
+        XCTAssertNil(PreciseDecimal(string: "abc"))
     }
 }
 
@@ -118,6 +202,15 @@ private extension InitTests {
         )
     }
 
+    func assertString(_ sut: String, _ expected: String, line: UInt = #line) throws {
+        let decimal = try XCTUnwrap(PreciseDecimal(string: sut)?.value)
+        assertDecimal(
+            decimal,
+            expected,
+            line: line
+        )
+    }
+
     func assertLiteral(_ preciseDecimal: PreciseDecimal, _ string: String, line: UInt = #line) {
         assertDecimal(
             preciseDecimal.value,