Merge pull request #4855 from 9rnsr/fix12829

Issue 12829 - Wrong error line number for closure allocation in @nogc function

src/declaration.h

@@ -654,6 +654,7 @@ class FuncDeclaration : public Declaration
     FuncDeclaration *isUnique();
     bool checkNestedReference(Scope *sc, Loc loc);
     bool needsClosure();
+    bool checkClosure();
     bool hasNestedFrameRefs();
     void buildResultVar(Scope *sc, Type *tret);
     Statement *mergeFrequire(Statement *);

src/func.d

@@ -2169,13 +2169,13 @@ public:
             sc2.callSuper = 0;
             sc2.pop();
         }
-        if (needsClosure())
+
+        if (checkClosure())
         {
-            if (setGC())
-                error("@nogc function allocates a closure with the GC");
-            else
-                printGCUsage(loc, "using closure causes GC allocation");
+            // We should be setting errors here instead of relying on the global error count.
+            //errors = true;
         }
+
         /* If function survived being marked as impure, then it is pure
          */
         if (flags & FUNCFLAGpurityInprocess)
@@ -3427,7 +3427,6 @@ public:
         for (size_t i = 0; i < closureVars.dim; i++)
         {
             VarDeclaration v = closureVars[i];
-            assert(v.isVarDeclaration());
             //printf("\tv = %s\n", v->toChars());
             for (size_t j = 0; j < v.nestedrefs.dim; j++)
             {
@@ -3496,6 +3495,65 @@ public:
         return true;
     }
 
+    /***********************************************
+     * Check that the function contains any closure.
+     * If it's @nogc, report suitable errors.
+     * This is mostly consistent with FuncDeclaration::needsClosure().
+     *
+     * Returns:
+     *      true if any errors occur.
+     */
+    final bool checkClosure()
+    {
+        if (!needsClosure())
+            return false;
+
+        if (setGC())
+        {
+            error("is @nogc yet allocates closures with the GC");
+            if (global.gag)     // need not report supplemental errors
+                return true;
+        }
+        else
+        {
+            printGCUsage(loc, "using closure causes GC allocation");
+            return false;
+        }
+
+        FuncDeclarations a;
+        foreach (v; closureVars)
+        {
+            foreach (f; v.nestedrefs)
+            {
+                assert(f !is this);
+
+            LcheckAncestorsOfANestedRef:
+                for (Dsymbol s = f; s && s !is this; s = s.parent)
+                {
+                    auto fx = s.isFuncDeclaration();
+                    if (!fx)
+                        continue;
+                    if (fx.isThis() ||
+                        fx.tookAddressOf ||
+                        checkEscapingSiblings(fx, this))
+                    {
+                        foreach (f2; a)
+                        {
+                            if (f2 == f)
+                                break LcheckAncestorsOfANestedRef;
+                        }
+                        a.push(f);
+                        .errorSupplemental(f.loc, "%s closes over variable %s at %s",
+                            f.toPrettyChars(), v.toChars(), v.loc.toChars());
+                        break LcheckAncestorsOfANestedRef;
+                    }
+                }
+            }
+        }
+
+        return true;
+    }
+
     /***********************************************
      * Determine if function's variables are referenced by a function
      * nested within it.

test/fail_compilation/diag12829.d

@@ -0,0 +1,37 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/diag12829.d(12): Error: function diag12829.test1 is @nogc yet allocates closures with the GC
+fail_compilation/diag12829.d(15):        diag12829.test1.__lambda1 closes over variable x at fail_compilation/diag12829.d(14)
+fail_compilation/diag12829.d(19):        diag12829.test1.bar closes over variable x at fail_compilation/diag12829.d(14)
+fail_compilation/diag12829.d(26): Error: function diag12829.test2 is @nogc yet allocates closures with the GC
+fail_compilation/diag12829.d(31):        diag12829.test2.S.foo closes over variable x at fail_compilation/diag12829.d(28)
+---
+*/
+
+auto test1() @nogc
+{
+    int x;
+    void delegate() @nogc foo = () {
+        int y = x;
+    };
+
+    void bar()
+    {
+        int y = x;
+    }
+    auto dg = &bar;
+}
+
+auto test2() @nogc
+{
+    int x;
+    struct S
+    {
+        void foo()
+        {
+            int y = x;
+        }
+    }
+    return S();
+}

test/fail_compilation/nogc3.d

@@ -44,8 +44,10 @@ fail_compilation/nogc3.d(36): Error: @nogc function 'nogc3.testCall' cannot call
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/nogc3.d(51): Error: function nogc3.testClosure1 @nogc function allocates a closure with the GC
-fail_compilation/nogc3.d(63): Error: function nogc3.testClosure3 @nogc function allocates a closure with the GC
+fail_compilation/nogc3.d(53): Error: function nogc3.testClosure1 is @nogc yet allocates closures with the GC
+fail_compilation/nogc3.d(56):        nogc3.testClosure1.bar closes over variable x at fail_compilation/nogc3.d(55)
+fail_compilation/nogc3.d(65): Error: function nogc3.testClosure3 is @nogc yet allocates closures with the GC
+fail_compilation/nogc3.d(68):        nogc3.testClosure3.bar closes over variable x at fail_compilation/nogc3.d(67)
 ---
 */
 @nogc auto testClosure1()