Allow JS multiple declarations of ctor properties

src/compiler/binder.ts

@@ -298,8 +298,10 @@ namespace ts {
             const name = isDefaultExport && parent ? "default" : getDeclarationName(node);
 
             let symbol: Symbol;
-            if (name !== undefined) {
-
+            if (name === undefined) {
+                symbol = createSymbol(SymbolFlags.None, "__missing");
+            }
+            else {
                 // Check and see if the symbol table already has a symbol with this name.  If not,
                 // create a new symbol with this name and add it to the table.  Note that we don't
                 // give the new symbol any flags *yet*.  This ensures that it will not conflict
@@ -327,33 +329,37 @@ namespace ts {
                 }
 
                 if (symbol.flags & excludes) {
-                    if (node.name) {
-                        node.name.parent = node;
+                    if (symbol.isDiscardable) {
+                        // Javascript constructor-declared symbols can be discarded in favor of
+                        // prototype symbols like methods.
+                        symbol = symbolTable[name] = createSymbol(SymbolFlags.None, name);
                     }
+                    else {
+                        if (node.name) {
+                            node.name.parent = node;
+                        }
 
-                    // Report errors every position with duplicate declaration
-                    // Report errors on previous encountered declarations
-                    let message = symbol.flags & SymbolFlags.BlockScopedVariable
-                        ? Diagnostics.Cannot_redeclare_block_scoped_variable_0
-                        : Diagnostics.Duplicate_identifier_0;
+                        // Report errors every position with duplicate declaration
+                        // Report errors on previous encountered declarations
+                        let message = symbol.flags & SymbolFlags.BlockScopedVariable
+                            ? Diagnostics.Cannot_redeclare_block_scoped_variable_0
+                            : Diagnostics.Duplicate_identifier_0;
 
-                    forEach(symbol.declarations, declaration => {
-                        if (declaration.flags & NodeFlags.Default) {
-                            message = Diagnostics.A_module_cannot_have_multiple_default_exports;
-                        }
-                    });
+                        forEach(symbol.declarations, declaration => {
+                            if (declaration.flags & NodeFlags.Default) {
+                                message = Diagnostics.A_module_cannot_have_multiple_default_exports;
+                            }
+                        });
 
-                    forEach(symbol.declarations, declaration => {
-                        file.bindDiagnostics.push(createDiagnosticForNode(declaration.name || declaration, message, getDisplayName(declaration)));
-                    });
-                    file.bindDiagnostics.push(createDiagnosticForNode(node.name || node, message, getDisplayName(node)));
+                        forEach(symbol.declarations, declaration => {
+                            file.bindDiagnostics.push(createDiagnosticForNode(declaration.name || declaration, message, getDisplayName(declaration)));
+                        });
+                        file.bindDiagnostics.push(createDiagnosticForNode(node.name || node, message, getDisplayName(node)));
 
-                    symbol = createSymbol(SymbolFlags.None, name);
+                        symbol = createSymbol(SymbolFlags.None, name);
+                    }
                 }
             }
-            else {
-                symbol = createSymbol(SymbolFlags.None, "__missing");
-            }
 
             addDeclarationToSymbol(symbol, node, includes);
             symbol.parent = parent;
@@ -1967,7 +1973,7 @@ namespace ts {
         }
 
         function bindThisPropertyAssignment(node: BinaryExpression) {
-            // Declare a 'member' in case it turns out the container was an ES5 class or ES6 constructor
+            // Declare a 'member' if the container is an ES5 class or ES6 constructor
             let assignee: Node;
             if (container.kind === SyntaxKind.FunctionDeclaration || container.kind === SyntaxKind.FunctionExpression) {
                 assignee = container;
@@ -1980,7 +1986,9 @@ namespace ts {
             }
             assignee.symbol.members = assignee.symbol.members || {};
             // It's acceptable for multiple 'this' assignments of the same identifier to occur
-            declareSymbol(assignee.symbol.members, assignee.symbol, node, SymbolFlags.Property, SymbolFlags.PropertyExcludes & ~SymbolFlags.Property);
+            // AND it can be overwritten by subsequent method declarations
+            const symbol = declareSymbol(assignee.symbol.members, assignee.symbol, node, SymbolFlags.Property, SymbolFlags.PropertyExcludes & ~SymbolFlags.Property);
+            symbol.isDiscardable = true;
         }
 
         function bindPrototypePropertyAssignment(node: BinaryExpression) {

src/compiler/types.ts

@@ -2137,6 +2137,7 @@ namespace ts {
         /* @internal */ exportSymbol?: Symbol;  // Exported symbol associated with this symbol
         /* @internal */ constEnumOnlyModule?: boolean; // True if module contains only const enums or other modules with only const enums
         /* @internal */ isReferenced?: boolean; // True if the symbol is referenced elsewhere
+        /* @internal */ isDiscardable?: boolean; // True if a Javascript class property can be overwritten by a method
     }
 
     /* @internal */

tests/baselines/reference/multipleDeclarations.js

@@ -1,11 +1,38 @@
 //// [input.js]
-
 function C() {
     this.m = null;
 }
 C.prototype.m = function() {
     this.nothing();
-};
+}
+class X {
+    constructor() {
+        this.m = this.m.bind(this);
+        this.mistake = 'frankly, complete nonsense';
+    }
+    m() {
+    }
+    mistake() {
+    }
+}
+let x = new X();
+X.prototype.mistake = false;
+x.m();
+x.mistake;
+class Y {
+    mistake() {
+    }
+    m() {
+    }
+    constructor() {
+        this.m = this.m.bind(this);
+        this.mistake = 'even more nonsense';
+    }
+}
+Y.prototype.mistake = true;
+let y = new Y();
+y.m();
+y.mistake();
 
 
 //// [output.js]
@@ -15,3 +42,33 @@ function C() {
 C.prototype.m = function () {
     this.nothing();
 };
+var X = (function () {
+    function X() {
+        this.m = this.m.bind(this);
+        this.mistake = 'frankly, complete nonsense';
+    }
+    X.prototype.m = function () {
+    };
+    X.prototype.mistake = function () {
+    };
+    return X;
+}());
+var x = new X();
+X.prototype.mistake = false;
+x.m();
+x.mistake;
+var Y = (function () {
+    function Y() {
+        this.m = this.m.bind(this);
+        this.mistake = 'even more nonsense';
+    }
+    Y.prototype.mistake = function () {
+    };
+    Y.prototype.m = function () {
+    };
+    return Y;
+}());
+Y.prototype.mistake = true;
+var y = new Y();
+y.m();
+y.mistake();

tests/baselines/reference/multipleDeclarations.symbols

@@ -1,19 +1,106 @@
 === tests/cases/conformance/salsa/input.js ===
-
 function C() {
 >C : Symbol(C, Decl(input.js, 0, 0))
 
     this.m = null;
->m : Symbol(C.m, Decl(input.js, 1, 14), Decl(input.js, 3, 1))
+>m : Symbol(C.m, Decl(input.js, 0, 14), Decl(input.js, 2, 1))
 }
 C.prototype.m = function() {
->C.prototype : Symbol(C.m, Decl(input.js, 1, 14), Decl(input.js, 3, 1))
+>C.prototype : Symbol(C.m, Decl(input.js, 0, 14), Decl(input.js, 2, 1))
 >C : Symbol(C, Decl(input.js, 0, 0))
 >prototype : Symbol(Function.prototype, Decl(lib.d.ts, --, --))
->m : Symbol(C.m, Decl(input.js, 1, 14), Decl(input.js, 3, 1))
+>m : Symbol(C.m, Decl(input.js, 0, 14), Decl(input.js, 2, 1))
 
     this.nothing();
 >this : Symbol(C, Decl(input.js, 0, 0))
+}
+class X {
+>X : Symbol(X, Decl(input.js, 5, 1))
+
+    constructor() {
+        this.m = this.m.bind(this);
+>this.m : Symbol(X.m, Decl(input.js, 10, 5))
+>this : Symbol(X, Decl(input.js, 5, 1))
+>m : Symbol(X.m, Decl(input.js, 7, 19))
+>this.m.bind : Symbol(Function.bind, Decl(lib.d.ts, --, --))
+>this.m : Symbol(X.m, Decl(input.js, 10, 5))
+>this : Symbol(X, Decl(input.js, 5, 1))
+>m : Symbol(X.m, Decl(input.js, 10, 5))
+>bind : Symbol(Function.bind, Decl(lib.d.ts, --, --))
+>this : Symbol(X, Decl(input.js, 5, 1))
+
+        this.mistake = 'frankly, complete nonsense';
+>this.mistake : Symbol(X.mistake, Decl(input.js, 12, 5))
+>this : Symbol(X, Decl(input.js, 5, 1))
+>mistake : Symbol(X.mistake, Decl(input.js, 8, 35))
+    }
+    m() {
+>m : Symbol(X.m, Decl(input.js, 10, 5))
+    }
+    mistake() {
+>mistake : Symbol(X.mistake, Decl(input.js, 12, 5))
+    }
+}
+let x = new X();
+>x : Symbol(x, Decl(input.js, 16, 3))
+>X : Symbol(X, Decl(input.js, 5, 1))
+
+X.prototype.mistake = false;
+>X.prototype.mistake : Symbol(X.mistake, Decl(input.js, 12, 5))
+>X : Symbol(X, Decl(input.js, 5, 1))
+>prototype : Symbol(X.prototype)
+
+x.m();
+>x.m : Symbol(X.m, Decl(input.js, 10, 5))
+>x : Symbol(x, Decl(input.js, 16, 3))
+>m : Symbol(X.m, Decl(input.js, 10, 5))
+
+x.mistake;
+>x.mistake : Symbol(X.mistake, Decl(input.js, 12, 5))
+>x : Symbol(x, Decl(input.js, 16, 3))
+>mistake : Symbol(X.mistake, Decl(input.js, 12, 5))
+
+class Y {
+>Y : Symbol(Y, Decl(input.js, 19, 10))
+
+    mistake() {
+>mistake : Symbol(Y.mistake, Decl(input.js, 20, 9), Decl(input.js, 26, 35))
+    }
+    m() {
+>m : Symbol(Y.m, Decl(input.js, 22, 5), Decl(input.js, 25, 19))
+    }
+    constructor() {
+        this.m = this.m.bind(this);
+>this.m : Symbol(Y.m, Decl(input.js, 22, 5), Decl(input.js, 25, 19))
+>this : Symbol(Y, Decl(input.js, 19, 10))
+>m : Symbol(Y.m, Decl(input.js, 22, 5), Decl(input.js, 25, 19))
+>this.m : Symbol(Y.m, Decl(input.js, 22, 5), Decl(input.js, 25, 19))
+>this : Symbol(Y, Decl(input.js, 19, 10))
+>m : Symbol(Y.m, Decl(input.js, 22, 5), Decl(input.js, 25, 19))
+>this : Symbol(Y, Decl(input.js, 19, 10))
+
+        this.mistake = 'even more nonsense';
+>this.mistake : Symbol(Y.mistake, Decl(input.js, 20, 9), Decl(input.js, 26, 35))
+>this : Symbol(Y, Decl(input.js, 19, 10))
+>mistake : Symbol(Y.mistake, Decl(input.js, 20, 9), Decl(input.js, 26, 35))
+    }
+}
+Y.prototype.mistake = true;
+>Y.prototype.mistake : Symbol(Y.mistake, Decl(input.js, 20, 9), Decl(input.js, 26, 35))
+>Y : Symbol(Y, Decl(input.js, 19, 10))
+>prototype : Symbol(Y.prototype)
+
+let y = new Y();
+>y : Symbol(y, Decl(input.js, 31, 3))
+>Y : Symbol(Y, Decl(input.js, 19, 10))
+
+y.m();
+>y.m : Symbol(Y.m, Decl(input.js, 22, 5), Decl(input.js, 25, 19))
+>y : Symbol(y, Decl(input.js, 31, 3))
+>m : Symbol(Y.m, Decl(input.js, 22, 5), Decl(input.js, 25, 19))
 
-};
+y.mistake();
+>y.mistake : Symbol(Y.mistake, Decl(input.js, 20, 9), Decl(input.js, 26, 35))
+>y : Symbol(y, Decl(input.js, 31, 3))
+>mistake : Symbol(Y.mistake, Decl(input.js, 20, 9), Decl(input.js, 26, 35))