chore: bump Motoko to v1.7.0

.sources/VERSIONS

@@ -50,7 +50,7 @@ chain-fusion-signer   v0.3.0
 papi                  v0.1.1                                                    168bc9d
 ic-pub-key            v1.0.1                                                    f89fa55
 icp-cli               v0.2.3                                                    caeac37
-motoko                v1.6.0                                                     b818df6
+motoko                v1.7.0                                                     1e65e26
 motoko-core           v2.4.0                                                    cd37dbf
 cdk-rs                ic-cdk v0.20.1 / ic-cdk-timers v1.0.0 / ic-cdk-executor v2.0.0  317f55c
 candid                2025-12-18  # candid v0.10.20, didc v0.5.4                2e4a2cf

docs/languages/motoko/reference/changelog.md

@@ -22,13 +22,34 @@ $(dfx cache show)/moc --version
 
 # Motoko compiler changelog
 
+## 1.7.0 (2026-04-29)
+
+* motoko (`moc`)
+
+  * feat: Add null-coalescing operator `??` (#5722).
+    `e1 ?? e2` evaluates to the unwrapped contents of `e1` when `e1` is `?v`,
+    otherwise to `e2`. The right-hand side is evaluated lazily (short-circuit).
+    For example, `opt ?? defaultValue` replaces the verbose
+    `switch opt { case (?v) v; case null defaultValue }`.
+    The right-hand side may be a block (e.g. `opt ?? { let x = 1; x }`),
+    a `do`-block, or a `Prim.trap` for fail-fast unwrapping. Because `{ ... }`
+    on the right is parsed as a block, a bare record literal must be wrapped
+    in extra braces or parentheses, e.g. `opt ?? ({ x = 0 })` or
+    `opt ?? {{ x = 0 }}`.
+
+  * perf: Compile enhanced multi-migration chains as per-step functions instead of one deeply-nested inlined expression, avoiding the wasm-function complexity limit hit by long chains (#6065).
+
+  * bugfix: Preserve GC-only roots (blob deduplication table, migration functions list) across graph-copy upgrades, and defer actor type compatibility checks to `ICStableRead` so enhanced multi-migration chains with multiple pending steps are accepted (#5993).
+
+  * bugfix: Clearer error when installing a Motoko canister over a non-Motoko or otherwise incompatible canister (#6044).
+
 ## 1.6.0 (2026-04-21)
 
 * motoko (`moc`)
 
-  * bugfix: Fix `moc.js` resolution of relative flag paths (e.g. `--enhanced-migration`, `--actor-idl`): resolve against the project root (via new `setProjectRoot` API) instead of the source file's directory, matching native `moc` behavior. The language server should call `setProjectRoot(path)` before processing files.
+  * feat: expose caller attributes feature through primitives (#5970).
 
-  * feat: expose caller attributes feature through prim (#5970)
+  * bugfix: Fix `moc.js` resolution of relative flag paths (e.g. `--enhanced-migration`, `--actor-idl`): resolve against the project root (via new `setProjectRoot` API) instead of the source file's directory, matching native `moc` behavior. The language server should call `setProjectRoot(path)` before processing files (#6015).
 
 ## 1.5.1 (2026-04-13)
 

docs/languages/motoko/reference/motoko-grammar.md

@@ -64,6 +64,7 @@ This section describes the concrete syntax, or grammar, of Motoko. The specifica
 <typ_un> ::= 
     <typ_nullary>
     '?' <typ_un>
+    '??' <typ_un>
     'weak' <typ_un>
 
 <typ_pre> ::= 
@@ -217,6 +218,7 @@ This section describes the concrete syntax, or grammar, of Motoko. The specifica
     '#' <id>
     '#' <id> <exp_nullary>
     '?' <exp_un>
+    '??' <exp_un>
     <unop> <exp_un>
     <unassign> <exp_un>
     'actor' <exp_plain>
@@ -237,6 +239,7 @@ This section describes the concrete syntax, or grammar, of Motoko. The specifica
 <exp_nondec> ::= 
     <exp_bin>
     <exp_bin> ':=' <exp>
+    <exp_bin> '??' <exp_nest>
     <exp_bin> <binassign> <exp>
     'return' <exp>?
     <parenthetical>? 'async' <exp_nest>
@@ -320,6 +323,7 @@ This section describes the concrete syntax, or grammar, of Motoko. The specifica
     '#' <id>
     '#' <id> <pat_nullary>
     '?' <pat_un>
+    '??' <pat_un>
     <unop> <lit>
 
 <pat_bin> ::=