[REG2.031] Issue 14965 - Forward reference to inferred return type of function call when using auto return type

src/dcast.d

@@ -1913,6 +1913,15 @@ extern (C++) Expression castTo(Expression e, Scope* sc, Type t)
                 }
             }
 
+            if (auto f = isFuncAddress(e))
+            {
+                if (f.checkForwardRef(e.loc))
+                {
+                    result = new ErrorExp();
+                    return;
+                }
+            }
+
             visit(cast(Expression)e);
         }
 
@@ -2134,6 +2143,15 @@ extern (C++) Expression castTo(Expression e, Scope* sc, Type t)
                 }
             }
 
+            if (auto f = isFuncAddress(e))
+            {
+                if (f.checkForwardRef(e.loc))
+                {
+                    result = new ErrorExp();
+                    return;
+                }
+            }
+
             visit(cast(Expression)e);
         }
 
@@ -2180,6 +2198,15 @@ extern (C++) Expression castTo(Expression e, Scope* sc, Type t)
                 }
             }
 
+            if (auto f = isFuncAddress(e))
+            {
+                if (f.checkForwardRef(e.loc))
+                {
+                    result = new ErrorExp();
+                    return;
+                }
+            }
+
             visit(cast(Expression)e);
         }
 

src/expression.d

@@ -3866,13 +3866,10 @@ public:
             if (!f.functionSemantic())
                 return new ErrorExp();
 
-            if (!f.type.deco)
-            {
-                const(char)* trailMsg = f.inferRetType ? "inferred return type of function call " : "";
-                .error(loc, "forward reference to %s'%s'", trailMsg, f.toChars());
+            if (!hasOverloads && f.checkForwardRef(loc))
                 return new ErrorExp();
-            }
-            FuncDeclaration fd = s.isFuncDeclaration();
+
+            auto fd = s.isFuncDeclaration();
             fd.type = f.type;
             return new VarExp(loc, fd, hasOverloads);
         }
@@ -8200,13 +8197,10 @@ public:
             L1:
                 {
                     assert(ds);
-                    if (FuncDeclaration f = ds.isFuncDeclaration())
+                    if (auto f = ds.isFuncDeclaration())
                     {
-                        if (!f.type.deco)
-                        {
-                            error("forward reference to %s", f.toChars());
+                        if (f.checkForwardRef(loc))
                             return new ErrorExp();
-                        }
                     }
                     const(char)* s = mangle(ds);
                     Expression e = new StringExp(loc, cast(void*)s, strlen(s));
@@ -9903,7 +9897,7 @@ public:
         if (!type)
         {
             e1 = e1org; // Bugzilla 10922, avoid recursive expression printing
-            error("forward reference to inferred return type of function call %s", toChars());
+            error("forward reference to inferred return type of function call '%s'", toChars());
             return new ErrorExp();
         }
         if (f && f.tintro)
@@ -9986,6 +9980,46 @@ public:
     }
 }
 
+FuncDeclaration isFuncAddress(Expression e, bool* hasOverloads = null)
+{
+    if (e.op == TOKaddress)
+    {
+        auto ae1 = (cast(AddrExp)e).e1;
+        if (ae1.op == TOKvar)
+        {
+            auto ve = cast(VarExp)ae1;
+            if (hasOverloads)
+                *hasOverloads = ve.hasOverloads;
+            return ve.var.isFuncDeclaration();
+        }
+        if (ae1.op == TOKdotvar)
+        {
+            auto dve = cast(DotVarExp)ae1;
+            if (hasOverloads)
+                *hasOverloads = dve.hasOverloads;
+            return dve.var.isFuncDeclaration();
+        }
+    }
+    else
+    {
+        if (e.op == TOKsymoff)
+        {
+            auto soe = cast(SymOffExp)e;
+            if (hasOverloads)
+                *hasOverloads = soe.hasOverloads;
+            return soe.var.isFuncDeclaration();
+        }
+        if (e.op == TOKdelegate)
+        {
+            auto dge = cast(DelegateExp)e;
+            if (hasOverloads)
+                *hasOverloads = dge.hasOverloads;
+            return dge.func.isFuncDeclaration();
+        }
+    }
+    return null;
+}
+
 /***********************************************************
  */
 extern (C++) final class AddrExp : UnaExp
@@ -10054,14 +10088,15 @@ public:
             error("cannot take address of %s", e1.toChars());
             return new ErrorExp();
         }
-        if (!e1.type.deco)
+
+        bool hasOverloads;
+        if (auto f = isFuncAddress(this, &hasOverloads))
+        {
+            if (!hasOverloads && f.checkForwardRef(loc))
+                return new ErrorExp();
+        }
+        else if (!e1.type.deco)
         {
-            /* No deco means semantic() was not run on the type.
-             * We have to run semantic() on the symbol to get the right type:
-             *  auto x = &bar;
-             *  pure: int bar() { return 1;}
-             * otherwise the 'pure' is missing from the type assigned to x.
-             */
             if (e1.op == TOKvar)
             {
                 VarExp ve = cast(VarExp)e1;

src/func.d

@@ -2321,6 +2321,29 @@ public:
         return !errors && !semantic3Errors;
     }
 
+    /****************************************************
+     * Check that this function type is properly resolved.
+     * If not, report "forward reference error" and return true.
+     */
+    final bool checkForwardRef(Loc loc)
+    {
+        if (!functionSemantic())
+            return true;
+
+        /* No deco means the functionSemantic() call could not resolve
+         * forward referenes in the type of this function.
+         */
+        if (!type.deco)
+        {
+            bool inSemantic3 = (inferRetType && semanticRun >= PASSsemantic3);
+            .error(loc, "forward reference to %s'%s'",
+                (inSemantic3 ? "inferred return type of function " : "").ptr,
+                toChars());
+            return true;
+        }
+        return false;
+    }
+
     // called from semantic3
     final VarDeclaration declareThis(Scope* sc, AggregateDeclaration ad)
     {

src/init.d

@@ -785,20 +785,14 @@ public:
                 se.error("cannot infer type from %s %s", se.sds.kind(), se.toChars());
             return new ErrorInitializer();
         }
+
         // Give error for overloaded function addresses
-        if (exp.op == TOKsymoff)
+        bool hasOverloads;
+        if (auto f = isFuncAddress(exp, &hasOverloads))
         {
-            SymOffExp se = cast(SymOffExp)exp;
-            if (se.hasOverloads && !se.var.isFuncDeclaration().isUnique())
-            {
-                exp.error("cannot infer type from overloaded function symbol %s", exp.toChars());
+            if (f.checkForwardRef(loc))
                 return new ErrorInitializer();
-            }
-        }
-        if (exp.op == TOKdelegate)
-        {
-            DelegateExp se = cast(DelegateExp)exp;
-            if (se.hasOverloads && se.func.isFuncDeclaration() && !se.func.isFuncDeclaration().isUnique())
+            if (hasOverloads && !f.isUnique())
             {
                 exp.error("cannot infer type from overloaded function symbol %s", exp.toChars());
                 return new ErrorInitializer();

src/mtype.d

@@ -7549,6 +7549,17 @@ public:
              * template functions.
              */
         }
+        if (auto f = exp.op == TOKvar    ? (cast(   VarExp)exp).var.isFuncDeclaration()
+                   : exp.op == TOKdotvar ? (cast(DotVarExp)exp).var.isFuncDeclaration() : null)
+        {
+            if (f.checkForwardRef(loc))
+                goto Lerr;
+        }
+        if (auto f = isFuncAddress(exp))
+        {
+            if (f.checkForwardRef(loc))
+                goto Lerr;
+        }
 
         Type t = exp.type;
         if (!t)

src/statement.d

@@ -1150,7 +1150,13 @@ public:
             exp = exp.addDtorHook(sc);
             if (checkNonAssignmentArrayOp(exp))
                 exp = new ErrorExp();
+            if (auto f = isFuncAddress(exp))
+            {
+                if (f.checkForwardRef(exp.loc))
+                    exp = new ErrorExp();
+            }
             discardValue(exp);
+
             exp = exp.optimize(WANTvalue);
             exp = checkGC(sc, exp);
             if (exp.op == TOKerror)
@@ -4386,6 +4392,11 @@ public:
             exp = resolveProperties(sc, exp);
             if (exp.checkType())
                 exp = new ErrorExp();
+            if (auto f = isFuncAddress(exp))
+            {
+                if (fd.inferRetType && f.checkForwardRef(exp.loc))
+                    exp = new ErrorExp();
+            }
             if (checkNonAssignmentArrayOp(exp))
                 exp = new ErrorExp();
 

test/fail_compilation/diag7747.d

@@ -1,7 +1,7 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/diag7747.d(8): Error: forward reference to inferred return type of function call 'fact'
+fail_compilation/diag7747.d(8): Error: forward reference to inferred return type of function call 'fact(n - 1)'
 ---
 */
 

test/fail_compilation/fail12236.d

@@ -1,12 +1,12 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/fail12236.d(16): Error: forward reference to inferred return type of function call 'f1'
+fail_compilation/fail12236.d(16): Error: forward reference to inferred return type of function 'f1'
 fail_compilation/fail12236.d(16):        while evaluating pragma(msg, f1.mangleof)
-fail_compilation/fail12236.d(21): Error: forward reference to f2
+fail_compilation/fail12236.d(21): Error: forward reference to inferred return type of function 'f2'
 fail_compilation/fail12236.d(21):        while evaluating pragma(msg, f2(T)(T).mangleof)
 fail_compilation/fail12236.d(27): Error: template instance fail12236.f2!int error instantiating
-fail_compilation/fail12236.d(31): Error: forward reference to __lambda1
+fail_compilation/fail12236.d(31): Error: forward reference to inferred return type of function '__lambda1'
 fail_compilation/fail12236.d(31):        while evaluating pragma(msg, __lambda1.mangleof)
 ---
 */

test/fail_compilation/fail14965.d

@@ -0,0 +1,38 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/fail14965.d(19): Error: forward reference to inferred return type of function 'foo1'
+fail_compilation/fail14965.d(20): Error: forward reference to inferred return type of function 'foo2'
+fail_compilation/fail14965.d(22): Error: forward reference to inferred return type of function 'bar1'
+fail_compilation/fail14965.d(23): Error: forward reference to inferred return type of function 'bar2'
+fail_compilation/fail14965.d(25): Error: forward reference to inferred return type of function 'baz1'
+fail_compilation/fail14965.d(26): Error: forward reference to inferred return type of function 'baz2'
+fail_compilation/fail14965.d(30): Error: forward reference to inferred return type of function 'foo1'
+fail_compilation/fail14965.d(31): Error: forward reference to inferred return type of function 'foo2'
+fail_compilation/fail14965.d(33): Error: forward reference to inferred return type of function 'bar1'
+fail_compilation/fail14965.d(34): Error: forward reference to inferred return type of function 'bar2'
+fail_compilation/fail14965.d(36): Error: forward reference to inferred return type of function 'baz1'
+fail_compilation/fail14965.d(37): Error: forward reference to inferred return type of function 'baz2'
+---
+*/
+
+auto foo1() { alias F = typeof(foo1); }     // TypeTypeof
+auto foo2() { alias FP = typeof(&foo2); }   // TypeTypeof
+
+auto bar1() { auto fp = &bar1; }            // ExpInitializer
+auto bar2() { auto fp = cast(void function())&bar2; }   // castTo
+
+auto baz1() { return &baz1; }               // ReturnStatement
+auto baz2() { (&baz2); }                    // ExpStatement
+
+class C
+{
+    auto foo1() { alias F = typeof(this.foo1); }
+    auto foo2() { alias FP = typeof(&this.foo2); }
+
+    auto bar1() { auto fp = &this.bar1; }
+    auto bar2() { auto dg = cast(void delegate())&this.bar2; }
+
+    auto baz1() { return &baz1; }
+    auto baz2() { (&baz2); }
+}

test/fail_compilation/ice12235.d

@@ -1,8 +1,8 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/ice12235.d(14): Error: forward reference to __lambda1
-fail_compilation/ice12235.d(15): Error: forward reference to __lambda1
+fail_compilation/ice12235.d(14): Error: forward reference to inferred return type of function '__lambda1'
+fail_compilation/ice12235.d(15): Error: forward reference to inferred return type of function '__lambda1'
 fail_compilation/ice12235.d(15):        while evaluating pragma(msg, __lambda1.mangleof)
 ---
 */

test/fail_compilation/test9176.d

@@ -1,15 +1,17 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/test9176.d(12): Error: forward reference to inferred return type of function call 'get'
+fail_compilation/test9176.d(13): Error: forward reference to inferred return type of function call 'get()'
 ---
 */
 
 void foo(int x) {}
 static assert(!is(typeof(foo(S()))));
 
-struct S {
+struct S
+{
     auto get() { return get(); }
     alias get this;
 }
+
 void main(){}