Fix a bug in coalescing types with GC

When a duplicate type is found is should no longer be considered used!

.travis.yml

@@ -172,7 +172,7 @@ matrix:
       install:
         - git clone https://github.com/WebAssembly/wabt
         - mkdir -p wabt/build
-        - (cd wabt/wabt && cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=sccache -DCMAKE_CXX_COMPILER_ARG1=c++ && cmake --build . -- -j4)
+        - (cd wabt/build && cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=sccache -DCMAKE_CXX_COMPILER_ARG1=c++ -DBUILD_TESTS=OFF && cmake --build . -- -j4)
         - export PATH=$PATH:`pwd`/wabt/build
       script: cargo test -p wasm-bindgen-gc
       if: branch = master

crates/gc/src/bitvec.rs

@@ -29,6 +29,15 @@ impl BitSet {
         }
     }
 
+    pub fn remove(&mut self, i: &u32) {
+        let i = *i as usize;
+        let idx = i / BITS;
+        let bit = 1 << (i % BITS);
+        if let Some(slot) = self.bits.get_mut(idx) {
+            *slot &= !bit;
+        }
+    }
+
     pub fn contains(&self, i: &u32) -> bool {
         let i = *i as usize;
         let idx = i / BITS;

crates/gc/src/lib.rs

@@ -51,7 +51,7 @@ impl Config {
 }
 
 fn run(config: &mut Config, module: &mut Module) {
-    let analysis = {
+    let mut analysis = {
         let mut cx = LiveContext::new(&module);
         cx.blacklist.insert("rust_eh_personality");
         cx.blacklist.insert("__indirect_function_table");
@@ -80,7 +80,7 @@ fn run(config: &mut Config, module: &mut Module) {
         cx.analysis
     };
 
-    let cx = RemapContext::new(&module, &analysis, config);
+    let cx = RemapContext::new(&module, &mut analysis, config);
     for i in (0..module.sections().len()).rev() {
         let retain = match module.sections_mut()[i] {
             Section::Unparsed { .. } => {
@@ -476,7 +476,7 @@ struct RemapContext<'a> {
 }
 
 impl<'a> RemapContext<'a> {
-    fn new(m: &Module, analysis: &'a Analysis, config: &'a Config) -> RemapContext<'a> {
+    fn new(m: &Module, analysis: &'a mut Analysis, config: &'a Config) -> RemapContext<'a> {
         let mut nfunctions = 0;
         let mut functions = Vec::new();
         let mut nglobals = 0;
@@ -494,6 +494,7 @@ impl<'a> RemapContext<'a> {
                 if analysis.types.contains(&(i as u32)) {
                     if let Some(prev) = map.get(&ty) {
                         types.push(*prev);
+                        analysis.types.remove(&(i as u32));
                         continue
                     }
                     map.insert(ty, ntypes);

crates/gc/tests/wat/remove-unused-type.wat

@@ -0,0 +1,34 @@
+(module
+  (type (func))
+  (type (func (param i32)))
+  (type (func (param i32)))
+  (type (func (result i32)))
+
+  (func $f1 (type 0))
+  (func $f2 (type 1))
+  (func $f3 (type 2))
+  (func $f4 (type 3)
+    i32.const 0
+  )
+
+  (export "a" (func $f1))
+  (export "b" (func $f2))
+  (export "c" (func $f3))
+  (export "d" (func $f4))
+  )
+
+;; STDOUT (update this section with `BLESS_TESTS=1` while running tests)
+;; (module
+;;   (type (;0;) (func))
+;;   (type (;1;) (func (param i32)))
+;;   (type (;2;) (func (result i32)))
+;;   (func $f1 (type 0))
+;;   (func $f2 (type 1) (param i32))
+;;   (func $f3 (type 1) (param i32))
+;;   (func $f4 (type 2) (result i32)
+;;     i32.const 0)
+;;   (export "a" (func $f1))
+;;   (export "b" (func $f2))
+;;   (export "c" (func $f3))
+;;   (export "d" (func $f4)))
+;; STDOUT