closes #32; fix missing diagnostic for duplicate qualifiers

index.html

@@ -88,6 +88,12 @@ <h2>C Declarations &amp; printf/scanf &#10132; Prose</h2>
         <div id="d-restrict-qualified-function" class="d-error" hidden>
             <span>Functions may not be restrict-qualified</span>
         </div>
+        <div id="d-duplicate-pointer-qualifier" class="d-error" hidden>
+            <span>Duplicate qualifier on pointer</span>
+        </div>
+        <div id="d-duplicate-function-qualifier" class="d-error" hidden>
+            <span>Duplicate qualifier on function</span>
+        </div>
         <div id="d-zero-size-array" class="d-warning" hidden>
             <span>Zero-size arrays are a non-standard extension</span>
         </div>

js/prose-decl.js

@@ -363,6 +363,18 @@ export class Explainer {
         }
     }
 
+    /**
+     * Checks whether there are duplicate qualifiers in the given list
+     * @param {string[]} qualifiers
+     * @param {'function' | 'pointer'} context
+     */
+    checkForDuplicateQualifiers(qualifiers, context) {
+        const withoutDuplicates = new Set(qualifiers.map(q => q === '_Atomic' ? 'atomic' : q))
+        if (withoutDuplicates.size !== qualifiers.length) {
+            this.showDiagnostic(`duplicate-${context}-qualifier`);
+        }
+    }
+
     /**
      * Throws if there is misuse of specifiers in the declaration specifier
      * sequence, depending on the provided kind of context.
@@ -508,6 +520,7 @@ export class Explainer {
                 break;
             }
             case '*': {
+                this.checkForDuplicateQualifiers(d.qualifiers, 'pointer');
                 const q = d.qualifiers
                     .sort(Explainer.compareSpecifiers)
                     .map(Explainer.remapSpecifierTextForReadability)
@@ -598,6 +611,7 @@ export class Explainer {
                     this.showDiagnostic('empty-function-parameters');
                 }
 
+                this.checkForDuplicateQualifiers(d.qualifiers, 'function');
                 let overrideFinal = d.qualifiers[d.qualifiers.length - 1];
                 if (!['override', 'final'].includes(overrideFinal)) {
                     overrideFinal = undefined;

test/test.js

@@ -258,4 +258,20 @@ describe('Examples', function () {
             assert.ok(!diagnostics.includes('constexpr-implicit-const'));
         });
     });
+
+    code = 'void() const const';
+    describe(code, function () {
+        const diagnostics = codeToProse(code).diagnostics;
+        it('rejects duplicate qualifiers on function', function() {
+            assert.ok(diagnostics.includes('duplicate-function-qualifier'));
+        });
+    });
+
+    code = 'void * const const';
+    describe(code, function () {
+        const diagnostics = codeToProse(code).diagnostics;
+        it('rejects duplicate qualifiers on pointer', function() {
+            assert.ok(diagnostics.includes('duplicate-pointer-qualifier'));
+        });
+    });
 });