Merge pull request #30287 from HassanElDesouky/SR-12311

[SR-12311] Improve diagnostic for read-only properties

Author: Harlan Haskins

include/swift/AST/DiagnosticsSema.def

@@ -1973,8 +1973,8 @@ WARNING(protocol_usable_from_inline_warn,none,
         "protocol %select{refined|used}0 by '@usableFromInline' protocol "
         "should be '@usableForInline' or public", (bool))
 ERROR(protocol_property_must_be_computed_var,none,
-      "immutable property requirement must be declared as 'var' with a "
-      "'{ get }' specifier", ())
+      "protocols cannot require properties to be immutable; declare read-only "
+      "properties by using 'var' with a '{ get }' specifier", ())
 ERROR(protocol_property_must_be_computed,none,
       "property in protocol must have explicit { get } or { get set } specifier",
       ())

test/decl/protocol/protocols.swift

@@ -17,7 +17,7 @@ protocol Test {
   var subminor : Int  // expected-error {{property in protocol must have explicit { get } or { get set } specifier}} {{21-21= { get <#set#> \}}}
   static var staticProperty: Int // expected-error{{property in protocol must have explicit { get } or { get set } specifier}} {{33-33= { get <#set#> \}}}
 
-  let bugfix // expected-error {{type annotation missing in pattern}} expected-error {{immutable property requirement must be declared as 'var' with a '{ get }' specifier}}
+  let bugfix // expected-error {{type annotation missing in pattern}} expected-error {{protocols cannot require properties to be immutable; declare read-only properties by using 'var' with a '{ get }' specifier}}
   var comment // expected-error {{type annotation missing in pattern}} expected-error {{property in protocol must have explicit { get } or { get set } specifier}}
 }
 
@@ -458,7 +458,7 @@ protocol ShouldntCrash {
   let fullName: String { get }  // expected-error {{'let' declarations cannot be computed properties}} {{3-6=var}}
 
   // <rdar://problem/17200672> Let in protocol causes unclear errors and crashes
-  let fullName2: String  // expected-error {{immutable property requirement must be declared as 'var' with a '{ get }' specifier}} {{3-6=var}} {{24-24= { get \}}}
+  let fullName2: String  // expected-error {{protocols cannot require properties to be immutable; declare read-only properties by using 'var' with a '{ get }' specifier}} {{3-6=var}} {{24-24= { get \}}}
 
   // <rdar://problem/16789886> Assert on protocol property requirement without a type
   var propertyWithoutType { get } // expected-error {{type annotation missing in pattern}}
@@ -514,7 +514,7 @@ class C4 : P4 { // expected-error {{type 'C4' does not conform to protocol 'P4'}
 // <rdar://problem/25185722> Crash with invalid 'let' property in protocol
 protocol LetThereBeCrash {
   let x: Int
-  // expected-error@-1 {{immutable property requirement must be declared as 'var' with a '{ get }' specifier}} {{13-13= { get \}}}
+  // expected-error@-1 {{protocols cannot require properties to be immutable; declare read-only properties by using 'var' with a '{ get }' specifier}} {{13-13= { get \}}}
   // expected-note@-2 {{declared here}}
 }
 

test/decl/var/properties.swift

@@ -884,7 +884,7 @@ protocol ProtocolWillSetDidSet4 {
   var a: Int { didSet willSet } // expected-error {{property in protocol must have explicit { get } or { get set } specifier}} {{14-32={ get <#set#> \}}} expected-error 2 {{expected get or set in a protocol property}}
 }
 protocol ProtocolWillSetDidSet5 {
-  let a: Int { didSet willSet }  // expected-error {{immutable property requirement must be declared as 'var' with a '{ get }' specifier}} {{3-6=var}} {{13-13= { get \}}} {{none}} expected-error 2 {{expected get or set in a protocol property}} expected-error {{'let' declarations cannot be computed properties}} {{3-6=var}}
+  let a: Int { didSet willSet }  // expected-error {{protocols cannot require properties to be immutable; declare read-only properties by using 'var' with a '{ get }' specifier}} {{3-6=var}} {{13-13= { get \}}} {{none}} expected-error 2 {{expected get or set in a protocol property}} expected-error {{'let' declarations cannot be computed properties}} {{3-6=var}}
 }
 
 var globalDidsetWillSet: Int {  // expected-error {{non-member observing properties require an initializer}}

test/decl/var/static_var.swift

@@ -177,8 +177,8 @@ protocol P {  // expected-note{{extended type declared here}}
   class var v2: Int { get } // expected-error {{class properties are only allowed within classes; use 'static' to declare a requirement fulfilled by either a static or class property}} {{3-8=static}}
   static final var v3: Int { get } // expected-error {{only classes and class members may be marked with 'final'}}
 
-  static let l1: Int // expected-error {{immutable property requirement must be declared as 'var' with a '{ get }' specifier}}
-  class let l2: Int // expected-error {{class properties are only allowed within classes; use 'static' to declare a requirement fulfilled by either a static or class property}} {{3-8=static}} expected-error {{immutable property requirement must be declared as 'var' with a '{ get }' specifier}}
+  static let l1: Int // expected-error {{protocols cannot require properties to be immutable; declare read-only properties by using 'var' with a '{ get }' specifier}}
+  class let l2: Int // expected-error {{class properties are only allowed within classes; use 'static' to declare a requirement fulfilled by either a static or class property}} {{3-8=static}} expected-error {{protocols cannot require properties to be immutable; declare read-only properties by using 'var' with a '{ get }' specifier}}
 }
 
 extension P {