TS 5: Add support for const type parameters

Author: Gerrit0

.config/.prettierignore

@@ -8,6 +8,7 @@
 ../src/test/renderer/specs
 ../src/test/renderer/testProject
 ../src/test/utils/options/readers/data/invalid2.json
+../src/test/converter2/behavior/constTypeParam.ts
 ../static/main.js
 ../example/docs/
 **/tmp

src/lib/converter/factories/signature.ts

@@ -284,10 +284,10 @@ function convertTypeParameters(
 
         // There's no way to determine directly from a ts.TypeParameter what it's variance modifiers are
         // so unfortunately we have to go back to the node for this...
-        const variance = getVariance(
-            param.getSymbol()?.declarations?.find(ts.isTypeParameterDeclaration)
-                ?.modifiers
-        );
+        const declaration = param
+            .getSymbol()
+            ?.declarations?.find(ts.isTypeParameterDeclaration);
+        const variance = getVariance(declaration?.modifiers);
 
         const paramRefl = new TypeParameterReflection(
             param.symbol.name,
@@ -296,6 +296,16 @@ function convertTypeParameters(
             parent,
             variance
         );
+
+        // No way to determine this from the type parameter itself, need to go back to the declaration
+        if (
+            declaration?.modifiers?.some(
+                (m) => m.kind === ts.SyntaxKind.ConstKeyword
+            )
+        ) {
+            paramRefl.flags.setFlag(ReflectionFlag.Const, true);
+        }
+
         context.registerReflection(paramRefl, param.getSymbol());
         context.trigger(ConverterEvents.CREATE_TYPE_PARAMETER, paramRefl);
 
@@ -329,6 +339,10 @@ export function createTypeParamReflection(
         context.scope,
         getVariance(param.modifiers)
     );
+    if (param.modifiers?.some((m) => m.kind === ts.SyntaxKind.ConstKeyword)) {
+        paramRefl.flags.setFlag(ReflectionFlag.Const, true);
+    }
+
     context.registerReflection(paramRefl, param.symbol);
 
     if (ts.isJSDocTemplateTag(param.parent)) {

src/lib/output/themes/default/partials/typeParameters.tsx

@@ -11,6 +11,7 @@ export function typeParameters(context: DefaultThemeRenderContext, typeParameter
                     {typeParameters?.map((item) => (
                         <li>
                             <h4>
+                                {item.flags.isConst && "const "}
                                 {item.varianceModifier ? `${item.varianceModifier} ` : ""}
                                 {item.name}
                                 {!!item.type && (

src/lib/output/themes/lib.tsx

@@ -98,6 +98,7 @@ export function renderTypeParametersSignature(
                     <span class="tsd-signature-symbol">{"<"}</span>
                     {join(<span class="tsd-signature-symbol">{", "}</span>, typeParameters, (item) => (
                         <>
+                            {item.flags.isConst && "const "}
                             {item.varianceModifier ? `${item.varianceModifier} ` : ""}
                             <span class="tsd-signature-type" data-tsd-kind={item.kindString}>
                                 {item.name}

src/test/behaviorTests.ts

@@ -142,6 +142,13 @@ export const behaviorTests: {
         );
     },
 
+    constTypeParam(project) {
+        const getNamesExactly = query(project, "getNamesExactly");
+        const typeParams = getNamesExactly.signatures?.[0].typeParameters;
+        equal(typeParams?.length, 1);
+        equal(typeParams[0].flags.isConst, true);
+    },
+
     declareGlobal(project) {
         equal(
             project.children?.map((c) => c.name),

src/test/converter2/behavior/constTypeParam.ts

@@ -0,0 +1,4 @@
+export type HasNames = { names: readonly string[] };
+export function getNamesExactly<const T extends HasNames>(arg: T): T["names"] {
+    return arg.names;
+}