Chore: Fix few build warnings, and make CI fail on warn

.github/workflows/examples.yml

@@ -33,6 +33,8 @@ jobs:
             --release
             --no-default-features
             --features mysql,postgres,sqlite
+        env:
+          RUSTFLAGS: -D warnings
 
       - uses: actions/upload-artifact@v3
         with:
@@ -157,10 +159,9 @@ jobs:
       # so we only check that it compiles.
       - name: Chat (Check)
         uses: actions-rs/cargo@v1
-        env:
         with:
           command: check
-          args: -p sqlx-example-postgres-check
+          args: -p sqlx-example-postgres-chat
 
       - name: Files (Setup)
         working-directory: examples/postgres/files

.github/workflows/sqlx.yml

@@ -55,13 +55,17 @@ jobs:
             --manifest-path sqlx-core/Cargo.toml
             --no-default-features
             --features json,offline,migrate,_rt-${{ matrix.runtime }},_tls-${{ matrix.tls }}
+        env:
+          RUSTFLAGS: -D warnings
 
       - uses: actions-rs/cargo@v1
         with:
           command: check
           args: >
             --no-default-features
             --features all-databases,_unstable-all-types,runtime-${{ matrix.runtime }},tls-${{ matrix.tls }},macros
+        env:
+          RUSTFLAGS: -D warnings
 
   test:
     name: Unit Test
@@ -189,7 +193,7 @@ jobs:
         env:
           SQLX_OFFLINE: true
           SQLX_OFFLINE_DIR: .sqlx
-          RUSTFLAGS: --cfg sqlite_ipaddr
+          RUSTFLAGS: -D warnings --cfg sqlite_ipaddr
           LD_LIBRARY_PATH: /tmp/sqlite3-lib
 
       # Test macros in offline mode (still needs DATABASE_URL to run)
@@ -233,7 +237,7 @@ jobs:
         env:
           # FIXME: needed to disable `ltree` tests in Postgres 9.6
           # but `PgLTree` should just fall back to text format
-          RUSTFLAGS: --cfg postgres_${{ matrix.postgres }}
+          RUSTFLAGS: -D warnings --cfg postgres_${{ matrix.postgres }}
         with:
           command: build
           args: >
@@ -289,7 +293,7 @@ jobs:
           SQLX_OFFLINE_DIR: .sqlx
           # FIXME: needed to disable `ltree` tests in Postgres 9.6
           # but `PgLTree` should just fall back to text format
-          RUSTFLAGS: --cfg postgres_${{ matrix.postgres }}
+          RUSTFLAGS: -D warnings --cfg postgres_${{ matrix.postgres }}
 
       # Test macros in offline mode (still needs DATABASE_URL to run)
       - uses: actions-rs/cargo@v1
@@ -399,7 +403,7 @@ jobs:
         env:
           SQLX_OFFLINE: true
           SQLX_OFFLINE_DIR: .sqlx
-          RUSTFLAGS: --cfg mysql_${{ matrix.mysql }}
+          RUSTFLAGS: -D warnings --cfg mysql_${{ matrix.mysql }}
 
       # Test macros in offline mode (still needs DATABASE_URL to run)
       # MySQL 5.7 supports TLS but not TLSv1.3 as required by RusTLS.
@@ -495,7 +499,7 @@ jobs:
         env:
           SQLX_OFFLINE: true
           SQLX_OFFLINE_DIR: .sqlx
-          RUSTFLAGS: --cfg mariadb_${{ matrix.mariadb }}
+          RUSTFLAGS: -D warnings --cfg mariadb_${{ matrix.mariadb }}
 
       # Test macros in offline mode (still needs DATABASE_URL to run)
       - uses: actions-rs/cargo@v1

sqlx-macros-core/src/database/mod.rs

@@ -39,10 +39,12 @@ pub trait DatabaseExt: Database {
     fn describe_blocking(query: &str, database_url: &str) -> sqlx_core::Result<Describe<Self>>;
 }
 
+#[allow(dead_code)]
 pub struct CachingDescribeBlocking<DB: DatabaseExt> {
     connections: Lazy<Mutex<HashMap<String, DB::Connection>>>,
 }
 
+#[allow(dead_code)]
 impl<DB: DatabaseExt> CachingDescribeBlocking<DB> {
     pub const fn new() -> Self {
         CachingDescribeBlocking {

sqlx-macros-core/src/test_attr.rs

@@ -1,15 +1,16 @@
-use proc_macro2::{Span, TokenStream};
+use proc_macro2::TokenStream;
 use quote::quote;
-use syn::LitStr;
 
+#[cfg(feature = "migrate")]
 struct Args {
-    fixtures: Vec<LitStr>,
+    fixtures: Vec<syn::LitStr>,
     migrations: MigrationsOpt,
 }
 
+#[cfg(feature = "migrate")]
 enum MigrationsOpt {
     InferredPath,
-    ExplicitPath(LitStr),
+    ExplicitPath(syn::LitStr),
     ExplicitMigrator(syn::Path),
     Disabled,
 }
@@ -89,7 +90,8 @@ fn expand_advanced(args: syn::AttributeArgs, input: syn::ItemFn) -> crate::Resul
             quote! { args.migrator(&#migrator); }
         }
         MigrationsOpt::InferredPath if !inputs.is_empty() => {
-            let migrations_path = crate::common::resolve_path("./migrations", Span::call_site())?;
+            let migrations_path =
+                crate::common::resolve_path("./migrations", proc_macro2::Span::call_site())?;
 
             if migrations_path.is_dir() {
                 let migrator = crate::migrate::expand_migrator(&migrations_path)?;

sqlx-sqlite/src/connection/mod.rs

@@ -258,7 +258,7 @@ impl LockedSqliteHandle<'_> {
     /// The progress handler callback must not do anything that will modify the database connection that invoked
     /// the progress handler. Note that sqlite3_prepare_v2() and sqlite3_step() both modify their database connections
     /// in this context.
-    pub fn set_progress_handler<F>(&mut self, num_ops: i32, mut callback: F)
+    pub fn set_progress_handler<F>(&mut self, num_ops: i32, callback: F)
     where
         F: FnMut() -> bool + Send + 'static,
     {