From 290caad40254101faf324a05360a142d0ed88301 Mon Sep 17 00:00:00 2001
From: Mohamed Hegazy <mhegazy@microsoft.com>
Date: Sun, 17 Jul 2016 23:51:17 -0700
Subject: [PATCH] Fix #9636: Report unused type paramters only on last
 declaration

---
 src/compiler/checker.ts                       | 13 +++--
 .../reference/unusedTypeParameters6.js        | 16 ++++++
 .../reference/unusedTypeParameters6.symbols   | 13 +++++
 .../reference/unusedTypeParameters6.types     | 13 +++++
 .../reference/unusedTypeParameters7.js        | 16 ++++++
 .../reference/unusedTypeParameters7.symbols   | 13 +++++
 .../reference/unusedTypeParameters7.types     | 13 +++++
 .../unusedTypeParameters8.errors.txt          | 11 ++++
 .../reference/unusedTypeParameters8.js        | 16 ++++++
 .../reference/unusedTypeParameters9.js        | 30 +++++++++++
 .../reference/unusedTypeParameters9.symbols   | 53 +++++++++++++++++++
 .../reference/unusedTypeParameters9.types     | 53 +++++++++++++++++++
 tests/cases/compiler/unusedTypeParameters6.ts |  8 +++
 tests/cases/compiler/unusedTypeParameters7.ts |  8 +++
 tests/cases/compiler/unusedTypeParameters8.ts |  8 +++
 tests/cases/compiler/unusedTypeParameters9.ts | 17 ++++++
 16 files changed, 298 insertions(+), 3 deletions(-)
 create mode 100644 tests/baselines/reference/unusedTypeParameters6.js
 create mode 100644 tests/baselines/reference/unusedTypeParameters6.symbols
 create mode 100644 tests/baselines/reference/unusedTypeParameters6.types
 create mode 100644 tests/baselines/reference/unusedTypeParameters7.js
 create mode 100644 tests/baselines/reference/unusedTypeParameters7.symbols
 create mode 100644 tests/baselines/reference/unusedTypeParameters7.types
 create mode 100644 tests/baselines/reference/unusedTypeParameters8.errors.txt
 create mode 100644 tests/baselines/reference/unusedTypeParameters8.js
 create mode 100644 tests/baselines/reference/unusedTypeParameters9.js
 create mode 100644 tests/baselines/reference/unusedTypeParameters9.symbols
 create mode 100644 tests/baselines/reference/unusedTypeParameters9.types
 create mode 100644 tests/cases/compiler/unusedTypeParameters6.ts
 create mode 100644 tests/cases/compiler/unusedTypeParameters7.ts
 create mode 100644 tests/cases/compiler/unusedTypeParameters8.ts
 create mode 100644 tests/cases/compiler/unusedTypeParameters9.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index d6db67d3fa8..5ca952f883f 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -13274,7 +13274,7 @@ namespace ts {
                         checkAsyncFunctionReturnType(<FunctionLikeDeclaration>node);
                     }
                 }
-                if (!(<FunctionDeclaration>node).body) {
+                if (noUnusedIdentifiers && !(<FunctionDeclaration>node).body) {
                     checkUnusedTypeParameters(node);
                 }
             }
@@ -14609,8 +14609,15 @@ namespace ts {
         function checkUnusedTypeParameters(node: ClassDeclaration | ClassExpression | FunctionDeclaration | MethodDeclaration | FunctionExpression | ArrowFunction | ConstructorDeclaration | SignatureDeclaration | InterfaceDeclaration) {
             if (compilerOptions.noUnusedLocals && !isInAmbientContext(node)) {
                 if (node.typeParameters) {
+                    // Only report errors on the last declaration for the type parameter container;
+                    // this ensures that all uses have been accounted for.
+                    const symbol = node.symbol && getMergedSymbol(node.symbol);
+                    const lastDeclaration = symbol && symbol.declarations && lastOrUndefined(symbol.declarations);
+                    if (lastDeclaration !== node) {
+                        return;
+                    }
                     for (const typeParameter of node.typeParameters) {
-                        if (!typeParameter.symbol.isReferenced) {
+                        if (!getMergedSymbol(typeParameter.symbol).isReferenced) {
                             error(typeParameter.name, Diagnostics._0_is_declared_but_never_used, typeParameter.symbol.name);
                         }
                     }
@@ -16119,7 +16126,7 @@ namespace ts {
 
             if (produceDiagnostics) {
                 checkTypeForDuplicateIndexSignatures(node);
-                checkUnusedTypeParameters(node);
+                registerForUnusedIdentifiersCheck(node);
             }
         }
 
diff --git a/tests/baselines/reference/unusedTypeParameters6.js b/tests/baselines/reference/unusedTypeParameters6.js
new file mode 100644
index 00000000000..4c2b3a9d0ba
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters6.js
@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/unusedTypeParameters6.ts] ////
+
+//// [a.ts]
+
+class C<T> { }
+
+//// [b.ts]
+interface C<T> { a: T; }
+
+//// [a.js]
+var C = (function () {
+    function C() {
+    }
+    return C;
+}());
+//// [b.js]
diff --git a/tests/baselines/reference/unusedTypeParameters6.symbols b/tests/baselines/reference/unusedTypeParameters6.symbols
new file mode 100644
index 00000000000..bf20b44d347
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters6.symbols
@@ -0,0 +1,13 @@
+=== tests/cases/compiler/a.ts ===
+
+class C<T> { }
+>C : Symbol(C, Decl(a.ts, 0, 0), Decl(b.ts, 0, 0))
+>T : Symbol(T, Decl(a.ts, 1, 8), Decl(b.ts, 0, 12))
+
+=== tests/cases/compiler/b.ts ===
+interface C<T> { a: T; }
+>C : Symbol(C, Decl(a.ts, 0, 0), Decl(b.ts, 0, 0))
+>T : Symbol(T, Decl(a.ts, 1, 8), Decl(b.ts, 0, 12))
+>a : Symbol(C.a, Decl(b.ts, 0, 16))
+>T : Symbol(T, Decl(a.ts, 1, 8), Decl(b.ts, 0, 12))
+
diff --git a/tests/baselines/reference/unusedTypeParameters6.types b/tests/baselines/reference/unusedTypeParameters6.types
new file mode 100644
index 00000000000..165862c0080
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters6.types
@@ -0,0 +1,13 @@
+=== tests/cases/compiler/a.ts ===
+
+class C<T> { }
+>C : C<T>
+>T : T
+
+=== tests/cases/compiler/b.ts ===
+interface C<T> { a: T; }
+>C : C<T>
+>T : T
+>a : T
+>T : T
+
diff --git a/tests/baselines/reference/unusedTypeParameters7.js b/tests/baselines/reference/unusedTypeParameters7.js
new file mode 100644
index 00000000000..d63f7a0edc3
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters7.js
@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/unusedTypeParameters7.ts] ////
+
+//// [a.ts]
+
+class C<T> { a: T; }
+
+//// [b.ts]
+interface C<T> { }
+
+//// [a.js]
+var C = (function () {
+    function C() {
+    }
+    return C;
+}());
+//// [b.js]
diff --git a/tests/baselines/reference/unusedTypeParameters7.symbols b/tests/baselines/reference/unusedTypeParameters7.symbols
new file mode 100644
index 00000000000..79704b437a6
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters7.symbols
@@ -0,0 +1,13 @@
+=== tests/cases/compiler/a.ts ===
+
+class C<T> { a: T; }
+>C : Symbol(C, Decl(a.ts, 0, 0), Decl(b.ts, 0, 0))
+>T : Symbol(T, Decl(a.ts, 1, 8), Decl(b.ts, 0, 12))
+>a : Symbol(C.a, Decl(a.ts, 1, 12))
+>T : Symbol(T, Decl(a.ts, 1, 8), Decl(b.ts, 0, 12))
+
+=== tests/cases/compiler/b.ts ===
+interface C<T> { }
+>C : Symbol(C, Decl(a.ts, 0, 0), Decl(b.ts, 0, 0))
+>T : Symbol(T, Decl(a.ts, 1, 8), Decl(b.ts, 0, 12))
+
diff --git a/tests/baselines/reference/unusedTypeParameters7.types b/tests/baselines/reference/unusedTypeParameters7.types
new file mode 100644
index 00000000000..a52b4cee7ec
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters7.types
@@ -0,0 +1,13 @@
+=== tests/cases/compiler/a.ts ===
+
+class C<T> { a: T; }
+>C : C<T>
+>T : T
+>a : T
+>T : T
+
+=== tests/cases/compiler/b.ts ===
+interface C<T> { }
+>C : C<T>
+>T : T
+
diff --git a/tests/baselines/reference/unusedTypeParameters8.errors.txt b/tests/baselines/reference/unusedTypeParameters8.errors.txt
new file mode 100644
index 00000000000..d7928d36900
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters8.errors.txt
@@ -0,0 +1,11 @@
+tests/cases/compiler/b.ts(1,13): error TS6133: 'T' is declared but never used.
+
+
+==== tests/cases/compiler/a.ts (0 errors) ====
+    
+    class C<T> { }
+    
+==== tests/cases/compiler/b.ts (1 errors) ====
+    interface C<T> { }
+                ~
+!!! error TS6133: 'T' is declared but never used.
\ No newline at end of file
diff --git a/tests/baselines/reference/unusedTypeParameters8.js b/tests/baselines/reference/unusedTypeParameters8.js
new file mode 100644
index 00000000000..0c34373d315
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters8.js
@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/unusedTypeParameters8.ts] ////
+
+//// [a.ts]
+
+class C<T> { }
+
+//// [b.ts]
+interface C<T> { }
+
+//// [a.js]
+var C = (function () {
+    function C() {
+    }
+    return C;
+}());
+//// [b.js]
diff --git a/tests/baselines/reference/unusedTypeParameters9.js b/tests/baselines/reference/unusedTypeParameters9.js
new file mode 100644
index 00000000000..8d82921b076
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters9.js
@@ -0,0 +1,30 @@
+//// [unusedTypeParameters9.ts]
+
+// clas + interface
+class C1<T> { }
+interface C1<T> { a: T; }
+
+// interface + class
+class C2<T> { a: T; }
+interface C2<T> { }
+
+// interfaces
+interface C3<T> { a(c: (p: T) => void): void; }
+interface C3<T> { b: string; }
+interface C3<T> { c: number; }
+interface C3<T> { d: boolean;  }
+interface C3<T> { e: any; }
+
+//// [unusedTypeParameters9.js]
+// clas + interface
+var C1 = (function () {
+    function C1() {
+    }
+    return C1;
+}());
+// interface + class
+var C2 = (function () {
+    function C2() {
+    }
+    return C2;
+}());
diff --git a/tests/baselines/reference/unusedTypeParameters9.symbols b/tests/baselines/reference/unusedTypeParameters9.symbols
new file mode 100644
index 00000000000..6c4f6aab71c
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters9.symbols
@@ -0,0 +1,53 @@
+=== tests/cases/compiler/unusedTypeParameters9.ts ===
+
+// clas + interface
+class C1<T> { }
+>C1 : Symbol(C1, Decl(unusedTypeParameters9.ts, 0, 0), Decl(unusedTypeParameters9.ts, 2, 15))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 2, 9), Decl(unusedTypeParameters9.ts, 3, 13))
+
+interface C1<T> { a: T; }
+>C1 : Symbol(C1, Decl(unusedTypeParameters9.ts, 0, 0), Decl(unusedTypeParameters9.ts, 2, 15))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 2, 9), Decl(unusedTypeParameters9.ts, 3, 13))
+>a : Symbol(C1.a, Decl(unusedTypeParameters9.ts, 3, 17))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 2, 9), Decl(unusedTypeParameters9.ts, 3, 13))
+
+// interface + class
+class C2<T> { a: T; }
+>C2 : Symbol(C2, Decl(unusedTypeParameters9.ts, 3, 25), Decl(unusedTypeParameters9.ts, 6, 21))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 6, 9), Decl(unusedTypeParameters9.ts, 7, 13))
+>a : Symbol(C2.a, Decl(unusedTypeParameters9.ts, 6, 13))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 6, 9), Decl(unusedTypeParameters9.ts, 7, 13))
+
+interface C2<T> { }
+>C2 : Symbol(C2, Decl(unusedTypeParameters9.ts, 3, 25), Decl(unusedTypeParameters9.ts, 6, 21))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 6, 9), Decl(unusedTypeParameters9.ts, 7, 13))
+
+// interfaces
+interface C3<T> { a(c: (p: T) => void): void; }
+>C3 : Symbol(C3, Decl(unusedTypeParameters9.ts, 7, 19), Decl(unusedTypeParameters9.ts, 10, 47), Decl(unusedTypeParameters9.ts, 11, 30), Decl(unusedTypeParameters9.ts, 12, 30), Decl(unusedTypeParameters9.ts, 13, 32))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 10, 13), Decl(unusedTypeParameters9.ts, 11, 13), Decl(unusedTypeParameters9.ts, 12, 13), Decl(unusedTypeParameters9.ts, 13, 13), Decl(unusedTypeParameters9.ts, 14, 13))
+>a : Symbol(C3.a, Decl(unusedTypeParameters9.ts, 10, 17))
+>c : Symbol(c, Decl(unusedTypeParameters9.ts, 10, 20))
+>p : Symbol(p, Decl(unusedTypeParameters9.ts, 10, 24))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 10, 13), Decl(unusedTypeParameters9.ts, 11, 13), Decl(unusedTypeParameters9.ts, 12, 13), Decl(unusedTypeParameters9.ts, 13, 13), Decl(unusedTypeParameters9.ts, 14, 13))
+
+interface C3<T> { b: string; }
+>C3 : Symbol(C3, Decl(unusedTypeParameters9.ts, 7, 19), Decl(unusedTypeParameters9.ts, 10, 47), Decl(unusedTypeParameters9.ts, 11, 30), Decl(unusedTypeParameters9.ts, 12, 30), Decl(unusedTypeParameters9.ts, 13, 32))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 10, 13), Decl(unusedTypeParameters9.ts, 11, 13), Decl(unusedTypeParameters9.ts, 12, 13), Decl(unusedTypeParameters9.ts, 13, 13), Decl(unusedTypeParameters9.ts, 14, 13))
+>b : Symbol(C3.b, Decl(unusedTypeParameters9.ts, 11, 17))
+
+interface C3<T> { c: number; }
+>C3 : Symbol(C3, Decl(unusedTypeParameters9.ts, 7, 19), Decl(unusedTypeParameters9.ts, 10, 47), Decl(unusedTypeParameters9.ts, 11, 30), Decl(unusedTypeParameters9.ts, 12, 30), Decl(unusedTypeParameters9.ts, 13, 32))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 10, 13), Decl(unusedTypeParameters9.ts, 11, 13), Decl(unusedTypeParameters9.ts, 12, 13), Decl(unusedTypeParameters9.ts, 13, 13), Decl(unusedTypeParameters9.ts, 14, 13))
+>c : Symbol(C3.c, Decl(unusedTypeParameters9.ts, 12, 17))
+
+interface C3<T> { d: boolean;  }
+>C3 : Symbol(C3, Decl(unusedTypeParameters9.ts, 7, 19), Decl(unusedTypeParameters9.ts, 10, 47), Decl(unusedTypeParameters9.ts, 11, 30), Decl(unusedTypeParameters9.ts, 12, 30), Decl(unusedTypeParameters9.ts, 13, 32))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 10, 13), Decl(unusedTypeParameters9.ts, 11, 13), Decl(unusedTypeParameters9.ts, 12, 13), Decl(unusedTypeParameters9.ts, 13, 13), Decl(unusedTypeParameters9.ts, 14, 13))
+>d : Symbol(C3.d, Decl(unusedTypeParameters9.ts, 13, 17))
+
+interface C3<T> { e: any; }
+>C3 : Symbol(C3, Decl(unusedTypeParameters9.ts, 7, 19), Decl(unusedTypeParameters9.ts, 10, 47), Decl(unusedTypeParameters9.ts, 11, 30), Decl(unusedTypeParameters9.ts, 12, 30), Decl(unusedTypeParameters9.ts, 13, 32))
+>T : Symbol(T, Decl(unusedTypeParameters9.ts, 10, 13), Decl(unusedTypeParameters9.ts, 11, 13), Decl(unusedTypeParameters9.ts, 12, 13), Decl(unusedTypeParameters9.ts, 13, 13), Decl(unusedTypeParameters9.ts, 14, 13))
+>e : Symbol(C3.e, Decl(unusedTypeParameters9.ts, 14, 17))
+
diff --git a/tests/baselines/reference/unusedTypeParameters9.types b/tests/baselines/reference/unusedTypeParameters9.types
new file mode 100644
index 00000000000..58a75e67297
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters9.types
@@ -0,0 +1,53 @@
+=== tests/cases/compiler/unusedTypeParameters9.ts ===
+
+// clas + interface
+class C1<T> { }
+>C1 : C1<T>
+>T : T
+
+interface C1<T> { a: T; }
+>C1 : C1<T>
+>T : T
+>a : T
+>T : T
+
+// interface + class
+class C2<T> { a: T; }
+>C2 : C2<T>
+>T : T
+>a : T
+>T : T
+
+interface C2<T> { }
+>C2 : C2<T>
+>T : T
+
+// interfaces
+interface C3<T> { a(c: (p: T) => void): void; }
+>C3 : C3<T>
+>T : T
+>a : (c: (p: T) => void) => void
+>c : (p: T) => void
+>p : T
+>T : T
+
+interface C3<T> { b: string; }
+>C3 : C3<T>
+>T : T
+>b : string
+
+interface C3<T> { c: number; }
+>C3 : C3<T>
+>T : T
+>c : number
+
+interface C3<T> { d: boolean;  }
+>C3 : C3<T>
+>T : T
+>d : boolean
+
+interface C3<T> { e: any; }
+>C3 : C3<T>
+>T : T
+>e : any
+
diff --git a/tests/cases/compiler/unusedTypeParameters6.ts b/tests/cases/compiler/unusedTypeParameters6.ts
new file mode 100644
index 00000000000..f445665f4ea
--- /dev/null
+++ b/tests/cases/compiler/unusedTypeParameters6.ts
@@ -0,0 +1,8 @@
+//@noUnusedLocals:true
+//@noUnusedParameters:true
+
+// @fileName: a.ts
+class C<T> { }
+
+// @fileName: b.ts
+interface C<T> { a: T; }
\ No newline at end of file
diff --git a/tests/cases/compiler/unusedTypeParameters7.ts b/tests/cases/compiler/unusedTypeParameters7.ts
new file mode 100644
index 00000000000..87b42d97650
--- /dev/null
+++ b/tests/cases/compiler/unusedTypeParameters7.ts
@@ -0,0 +1,8 @@
+//@noUnusedLocals:true
+//@noUnusedParameters:true
+
+// @fileName: a.ts
+class C<T> { a: T; }
+
+// @fileName: b.ts
+interface C<T> { }
\ No newline at end of file
diff --git a/tests/cases/compiler/unusedTypeParameters8.ts b/tests/cases/compiler/unusedTypeParameters8.ts
new file mode 100644
index 00000000000..4034ed04c72
--- /dev/null
+++ b/tests/cases/compiler/unusedTypeParameters8.ts
@@ -0,0 +1,8 @@
+//@noUnusedLocals:true
+//@noUnusedParameters:true
+
+// @fileName: a.ts
+class C<T> { }
+
+// @fileName: b.ts
+interface C<T> { }
\ No newline at end of file
diff --git a/tests/cases/compiler/unusedTypeParameters9.ts b/tests/cases/compiler/unusedTypeParameters9.ts
new file mode 100644
index 00000000000..48581d4ab2e
--- /dev/null
+++ b/tests/cases/compiler/unusedTypeParameters9.ts
@@ -0,0 +1,17 @@
+//@noUnusedLocals:true
+//@noUnusedParameters:true
+
+// clas + interface
+class C1<T> { }
+interface C1<T> { a: T; }
+
+// interface + class
+class C2<T> { a: T; }
+interface C2<T> { }
+
+// interfaces
+interface C3<T> { a(c: (p: T) => void): void; }
+interface C3<T> { b: string; }
+interface C3<T> { c: number; }
+interface C3<T> { d: boolean;  }
+interface C3<T> { e: any; }
\ No newline at end of file