Fix Issue 19731 - auto struct methods whose address is taken don't test invariants

src/dmd/dsymbolsem.d

@@ -4209,6 +4209,42 @@ private extern(C++) final class DsymbolSemanticVisitor : Visitor
         funcDeclarationSemantic(deld);
     }
 
+    /* https://issues.dlang.org/show_bug.cgi?id=19731
+     *
+     * Some aggregate member functions might have had
+     * semantic 3 ran on them despite being in semantic1
+     * (e.g. auto functions); if that is the case, then
+     * invariants will not be taken into account for them
+     * because at the time of the analysis it would appear
+     * as if the struct declaration does not have any
+     * invariants. To solve this issue, we need to redo
+     * semantic3 on the function declaration.
+     */
+    private void reinforceInvariant(AggregateDeclaration ad, Scope* sc)
+    {
+        // for each member
+        for(int i = 0; i < ad.members.dim; i++)
+        {
+            if (!(*ad.members)[i])
+                continue;
+            auto fd = (*ad.members)[i].isFuncDeclaration();
+            if (!fd || fd.generated || fd.semanticRun != PASS.semantic3done)
+                continue;
+
+            /* if it's a user defined function declaration and semantic3
+             * was already performed on it, create a syntax copy and
+             * redo the first semantic step.
+             */
+            auto err = global.startGagging();
+            auto fd_temp = fd.syntaxCopy(null);
+            if (auto cd = ad.isClassDeclaration())
+                cd.vtbl.remove(fd.vtblIndex);
+            fd_temp.dsymbolSemantic(sc);
+            global.endGagging(err);
+            (*ad.members)[i] = fd_temp;
+        }
+    }
+
     override void visit(StructDeclaration sd)
     {
         //printf("StructDeclaration::semantic(this=%p, '%s', sizeok = %d)\n", sd, sd.toPrettyChars(), sd.sizeok);
@@ -4356,6 +4392,8 @@ private extern(C++) final class DsymbolSemanticVisitor : Visitor
         }
 
         sd.inv = buildInv(sd, sc2);
+        if (sd.inv)
+            reinforceInvariant(sd, sc2);
 
         Module.dprogress++;
         sd.semanticRun = PASS.semanticdone;
@@ -4980,6 +5018,8 @@ private extern(C++) final class DsymbolSemanticVisitor : Visitor
         }
 
         cldec.inv = buildInv(cldec, sc2);
+        if (cldec.inv)
+            reinforceInvariant(cldec, sc2);
 
         Module.dprogress++;
         cldec.semanticRun = PASS.semanticdone;

test/runnable/test19731.d

@@ -0,0 +1,53 @@
+// PERMUTE_ARGS:
+struct Foo
+{
+    Object obj_;
+
+    invariant (obj_ !is null);
+
+    auto obj7()
+    {
+        return this.obj_;
+    }
+
+    enum compiles = __traits(compiles, &Foo.init.obj7);
+}
+
+class Foo2
+{
+    Object obj_;
+
+    invariant (obj_ !is null);
+
+    final auto obj7()
+    {
+        return this.obj_;
+    }
+
+    enum compiles = __traits(compiles, &Foo.init.obj7);
+}
+
+void main()
+{
+    import core.exception : AssertError;
+    Foo foo = Foo();
+    Foo2 foo2 = new Foo2();
+
+    try
+    {
+        foo.obj7.toString();
+    }
+    catch(AssertError)
+    {
+        try
+        {
+            foo2.obj7.toString();
+        }
+        catch(AssertError)
+        {
+            return;
+        }
+        assert(0);
+    }
+    assert(0);
+}