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Avoid synthesizing the parameterless struct constructor unnecessarily #72314

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Feb 28, 2024
Merged

Avoid synthesizing the parameterless struct constructor unnecessarily #72314

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4 changes: 3 additions & 1 deletion src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4663,7 +4663,9 @@ private void AddSynthesizedConstructorsIfNecessary(MembersAndInitializersBuilder
}

//kick out early if we've seen everything we're looking for
if (hasInstanceConstructor && hasStaticConstructor)
if (hasInstanceConstructor &&
hasParameterlessInstanceConstructor &&
hasStaticConstructor)
{
break;
}
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106 changes: 106 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/StructConstructorTests.cs
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Expand Up @@ -4792,5 +4792,111 @@ .maxstack 2
}
");
}

[Theory]
[InlineData("class")]
[InlineData("struct")]
[WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1598252")]
public void StaticAndInstanceConstructors_01(string type)
{
string source = $$"""
using System;
{{type}} S
{
static S()
{
Console.WriteLine("static constructor");
}
public S(int p)
{
Console.WriteLine("instance constructor: {0}", p);
}
public S() : this(0)
{
}
}
class Program
{
static void Main()
{
_ = new S();
}
}
""";

var comp = CreateCompilation(source, options: TestOptions.ReleaseExe);
VerifyExplicitlyDeclaredInstanceConstructors(
comp.GlobalNamespace.GetTypeMember("S"),
"S..ctor(System.Int32 p)",
"S..ctor()");
VerifyExplicitlyDeclaredInstanceConstructors(
((Compilation)comp).GlobalNamespace.GetTypeMember("S"),
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What is the difference when obtaining the type symbol in this way, versus without the cast?

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The symbols from Compilation are public API ISymbol, while the symbols from CSharpCompilation are internal Symbol. Since the ISymbol instances are generated from the Symbol instances, this additional test may not be that useful, but it seemed simple to include.

"S..ctor(System.Int32 p)",
"S..ctor()");

CompileAndVerify(comp, expectedOutput: """
static constructor
instance constructor: 0
""");
}

[Theory]
[InlineData("class")]
[InlineData("struct")]
public void StaticAndInstanceConstructors_02(string type)
{
string source = $$"""
using System;
{{type}} S
{
static S()
{
Console.WriteLine("static constructor");
}
public S()
{
Console.WriteLine("instance constructor");
}
}
class Program
{
static void Main()
{
_ = new S();
}
}
""";

var comp = CreateCompilation(source, options: TestOptions.ReleaseExe);
VerifyExplicitlyDeclaredInstanceConstructors(
comp.GlobalNamespace.GetTypeMember("S"),
"S..ctor()");
VerifyExplicitlyDeclaredInstanceConstructors(
((Compilation)comp).GlobalNamespace.GetTypeMember("S"),
"S..ctor()");

CompileAndVerify(comp, expectedOutput: """
static constructor
instance constructor
""");
}

private static void VerifyExplicitlyDeclaredInstanceConstructors(NamedTypeSymbol type, params string[] expectedConstructors)
{
var constructors = type.InstanceConstructors;
var members = type.GetMembers(".ctor");
Assert.True(members.SequenceEqual(constructors));
Assert.True(constructors.All(c => c is { IsStatic: false, IsImplicitConstructor: false }));
Assert.Equal(expectedConstructors, constructors.ToTestDisplayStrings());
}

private static void VerifyExplicitlyDeclaredInstanceConstructors(INamedTypeSymbol type, params string[] expectedConstructors)
{
var constructors = type.InstanceConstructors;
var members = type.GetMembers(".ctor");
Assert.True(members.SequenceEqual(constructors));
Assert.True(constructors.All(c => c is { IsStatic: false, IsImplicitlyDeclared: false }));
Assert.Equal(expectedConstructors, constructors.ToTestDisplayStrings());
}
}
}
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